Archive of news items from the academic webpage of Howard Haber

This website contains an archive of news items that previously appeared on Howard Haber's academic web page.

News items from 2024

December 3, 2024: My paper in collaboration with Sumit Banik, Guglielmo Coloretti, and Andreas Crivellin, entitled Correlating EDMs and A→γγ in the 2HDM in light of the diphoton excesses at 95 GeV and 152 GeV, was posted on the arXiv. A link to this paper can be found in Section II of this website.

The correlations of Higgs decays to photons and with electric dipole moments (EDMs) in the CP-violating flavor-aligned two-Higgs-doublet model (2HDM) are examined. In the approximate alignment limit of the 2HDM (favored by the LHC Higgs data), the neutral scalar spectrum consists of a Standard Model (SM)-like Higgs boson and two approximate eigenstates of CP (denoted by the CP-even H and the CP-odd A). Nevertheless, CP-violating effects in the scalar self-couplings may be present such as a coupling of A to a pair of charged scalars H⁺H^-, which can yield (via a loop-induced process) a sizable branching ratio for A→γγ. These CP-violating effects also generate non-zero EDMs for the electron, the neutron and the proton. We examine these correlations for the cases of m_A=95 GeV and m_A=152 GeV where interesting excesses in the diphoton spectrum have been observed at the LHC. These excesses can be explained via the decay of A while being consistent with the experimental bound for the electron EDM in regions of parameter space that can be tested with future neutron and proton EDM measurements.

October 25, 2024: My talk entitled Flavor-nondiagonal neutral Higgs Yukawa couplings revisited, given at the Extended Scalar Sectors From All Angles workshop at CERN, has been posted to Section VII of this website.

September 4, 2024: My paper entitled Explicit form for the most general Lorentz transformation revisited was published in the journal Symmetry. A link to this paper can be found in Section II of this website.

Explicit formuale for the 4x4 Lorentz transformation matrices corresponding to a pure boost and a pure three-dimensional rotation are very well-known. Significantly less well-known is the explicit formula for a general Lorentz transformation with arbitrary boost and rotation parameters. We revisit this more general formula by presenting two different derivations, which are shown to yield the same result. The first derivation evaluates the exponential of a 4x4 matrix by making use of the Lagrange interpolating polynomial. The second derivation exploits the assertion that for two-component spinors η and χ, the spinor product ησ^μχ^† is a Lorentz four-vector. As a result, the formula for a general Lorentz transformation reduces to the computation of the trace of a product of 2x2 matrices.

September 3, 2024: My talk entitled Flavor-nondiagonal neutral Higgs Yukawa couplings revisited, given at the 2024 Workshop on Multi-Higgs Models in Lisbon, Portugal, at the Instituto Superior Técnico, has been posted to Section VII of this website.

August 1, 2024: The 2024 edition of the Review of Particle Physics, published today in Physical Review D, provides a comprehensive review of the field of particle physics and of related areas in cosmology. Topics include Higgs bosons, supersymmetry, big bang nucleosynthesis, probability, statistics, and accelerators and detectors. The latest update of my Supersymmetry Theory review in collaboration with Ben Allanach, which appears in the Review of Particle Physics, can be found in Section III of the academic website.

June 10, 2024: My talk entitled Classes of complete dark photon models constrained by Z Physics, given at the 31st International Conference on Supersymmetry and Unification of Fundamental Interactions: Theory meets Experiment (SUSY 2024), has been posted to Section VII of the academic website.

June 5, 2024: My talk entitled Flavor-nondiagonal neutral Higgs Yukawa couplings revisited, given at PLANCK 2024: 26th International Conference from the Planck Scale to the Electroweak Scale, has been posted to Section VII of the academic website.

May 1, 2024: My talk entitled Classes of complete dark photon models constrained by Z Physics, given at the CATCH22+2 International Conference at the Dublin Institute for Advanced Studies in Dublin, Ireland, has been posted to Section VII of the academic website.

March 12, 2024: My presentation to Physics 205 can be found in Section V of the academic website.

March 1, 2024: Some notes entitled Acceleration and Force in Special Relativity, which include a treatment of the instantaneous rest frame of an accelerating particle, have been posted to Section VI of the academic website.

February 28, 2024: A pedagogical presentation of the Thomas precession and the celebrated BMT equation has been posted to Section VI of the academic website.

February 25, 2024: Some notes on the origin of vector spherical harmonics entitled The tensor spherical harmonics, which employs the formalism of addition of angular momentum in quantum mechanics, has been posted to Section VI of the academic website. In the ﬁnal section of these notes, the application of vector spherical harmonics to the electromagnetic multipole radiation ﬁelds is exhibited.

February 19, 2024: I could not find in the literature closed-form expressions for the two-loop Barr-Zee diagram integrals. So, I went ahead and derived these results, which can be expressed in terms of dilogarithms or the Clausen function (depending on the value of a parameter). A short note presenting the derivation, entitled Evaluating integrals arising from Barr-Zee diagrams, has been posted to Section VI of the academic website.

February 13, 2024: Today, my paper in collaboration with Miguel Bento and Joao Silva, entitled Classes of complete dark photon models constrained by Z-physics, was published in Physics Letters B. A link to this paper can be found in Section II of thise academic website.

Dark Matter models that employ a vector portal to a dark sector are usually treated as an effective theory that incorporates kinetic mixing of the photon with a new U(1) gauge boson, with the Z boson integrated out. However, a more complete theory must employ the full SU(2)_L×U(1)_Y×U(1)_Y' gauge group, in which kinetic mixing of the Z boson with the new U(1) gauge boson is taken into account. The importance of the more complete analysis is demonstrated by an example where the parameter space of the effective theory that yields the observed dark matter relic density is in conflict with a suitably defined electroweak ρ parameter that is deduced from a global fit to Z physics data.

January 9, 2024: The 2023 update of the Supersymmetry (Theory) review that appears in the Review of Particle Physics by the Particle Data Group (PDG) was published online on December 1, 2023 (see news item below). To make it widely accessuble, this review was posted on the arXiv today. A link to the arXiv version of this review can be found in Section II of this website.

News items from 2023

December 29, 2023: The 2024 Particle Physics conference schedule has been posted to Section VIII of this website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

December 21, 2023: My paper entitled Explicit form for the most general Lorentz transformation revisited was posted on the arXiv. A link to this paper can be found in Section II of this website.

December 1, 2023: The 2023 update of the review articles appearing the Review of Particle Physics by the Particle Data Group (PDG) is now published on the PDG web site. Included among these review articles is the newly revised Supersymmetry, Part I (Theory), which is co-authored by myself and Ben Allanach.

November 10, 2023: Today, my paper in collaboration with Miguel Bento and Joao Silva, entitled Classes of complete dark photon models constrained by Z-physics, was posted on the arXiv. A link to this paper can be found in Section II of thise academic website.

October 30, 2023: Today, my paper entitled Higgs Boson Physics: The View Ahead was published in a special issue of Letters in High Energy Physics (LHEP) on Higgs physics, and beyond, after 10 years since the discovery. A link to this paper can be found in Section II of the academic website.

October 13, 2023: Today, my paper in collaboration with Miguel Bento and Joao Silva, entitled Tree-level Unitarity in SU(2)_L×U(1)_Y×U(1)_Y' Models, was published in JHEP. A link to this paper can be found in Section II of the academic website.

In models with a U(1) gauge extension beyond the Standard Model, one can derive sum rules for the couplings of the theory that are a consequence of tree-level unitarity. In this paper, we provide a comprehensive list of coupling sum rules for a general SU(2)_L×U(1)_Y×U(1)_Y' gauge theory coupled to an arbitrary set of fermion and scalar multiplets. For the case of a minimal extension of the Standard Model with a U(1)_Y' gauge boson, the definitions of the weak mixing angle and the electroweak ρ parameter are clarified, and a generalized ρ parameter (denoted by ρ′) is defined. The latter naturally follows from the unitarity sum rules developed in this paper.

September 28, 2023: Today, my paper in collaboration with Joseph (Zippy) Connel and Pedro Ferreira, entitled Accommodating Hints of New Heavy Scalars in the Framework of the Flavor-Aligned Two-Higgs-Doublet Model, was published in Physical Review D. A link to this paper can be found in Section II of the academic website.

Searches for new neutral Higgs bosons of an extended Higgs sector at the LHC can be interpreted in the framework of the two-Higgs doublet model. By employing generic flavor-aligned Higgs–fermion Yukawa couplings, we propose an analysis that uses experimental data to determine whether flavor alignment is a consequence of a symmetry that is either exact or at most softly broken. We illustrate our proposal in two different scenarios based on a few 3 sigma (local) excesses observed by the ATLAS and CMS Collaborations in their searches for heavy scalars at Run 2 of the LHC.

September 13, 2023: My talk entitled Scalar revelations at future e⁺e^- colliders, given at Scalars 2023 at the University of Warsaw in Warsaw, Poland, has been posted to Section VII of the academic website.

September 6, 2023: My talk entitled Signals of new heavy scalars in the flavor-aligned 2HDM, given at Higgs Days at Santander 2023, has been posted to Section VII of the academic website.

July 21, 2023: My talk entitled Supersymmetry Confronts a SM-Like Higgs Boson, given at the XXX International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2023), has been posted to Section VII of the academic website.

July 13, 2023: Two lectures, entitled Supersymmetry and Higgs Physics were presented today at the pre-SUSY school 2023 at the University of Southampton in Southampton, England. This four day school precedes the The XXX International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2023), which will take place the following week. The lecture slides have been posted to Section VII of the academic website.

June 30, 2023: Physical copies of our textbook, From Spinors to Supersymmetry, co-authored by Herbi K. Dreiner, Howard E. Haber and Stephen P. Martin, have now arrived from the publisher. On the following day, I made the ten-mile bike ride from the Aspen Center for Physics to Maroon Lake (elevation gain of 1700 ft.), which is one of my favorite bike rides that I have done many times before. But, on this ride, I took along a copy of the book in order to have the following photo taken:

June 7, 2023: The textbook, entitled From Spinors to Supersymmetry, co-authored by Herbi K. Dreiner, Howard E. Haber and Stephen P. Martin, is now officially published and available from Cambridge University Press. Click here for an overview. For further details on purchasing a copy, check out this link . It is also available from Amazon via the following link.

June 6, 2023: Today, my paper in collaboration with Miguel Bento and Joao Silva, entitled Tree-level Unitarity in SU(2)_L×U(1)_Y×U(1)_Y' Models, was posted on the arXiv. A link to this paper can be found in Section II of the academic website.

June 5, 2023: My talk entitled Signals of new heavy scalars in the flavor-aligned 2HDM, given at the 6th International Workshop on "Higgs as a Probe of New Physics" (HPNP2023), at Osaka University, in Osaka, Japan, has been posted to Section VII of the academic website.

May 28, 2023: My talk entitled My Journey through Physics with Marcela and Carlos, given at Beyond the SM from Colliders to the Early Universe: a symposium in honor of Marcela Carena and Carlos Wagner on the occasion of their 60th birthdays, at the University of Chicago in Chicago, IL USA, has been posted to Section VII of the academic website.

May 22, 2023: My talk entitled Higgs Boson Physics—The View Ahead, given at PLANCK 2023: The 25th International Conference from the Planck Scale to the Electroweak Scale, at the University of Warsaw in Warsaw, Poland, has been posted to Section VII of the academic website.

May 17, 2023: My talk entitled P-even, CP-violating Signals in ScalarMediated Processes, given at the International Workshop on Future Linear Colliders (LCWS2023), at SLAC National Accelerator Laboraotry in Menlo Park, CA USA, has been posted to Section VII of the academic website.

March 28, 2023: My talk entitled Adventures from spinors to SUSY, given at the "Herbi Fest"--Pursuing Physics Beyond the Standard Model: a symposium in honor of Herbi Dreiner on the occasion of his 60th birthday, at the Bethe Center for Theoretical Physics, University of Bonn, in Bonn, Germany, has been posted to Section VII of the academic website.

March 7, 2023: My presentation to Physics 205 can be found in Section V of the academic website.

February 28, 2023: Today, my paper in collaboration with Joseph (Zippy) Connel and Pedro Ferreira, entitled Accommodating Hints of New Heavy Scalars in the Framework of the Flavor-Aligned Two-Higgs-Doublet Model, was posted on the arXiv. A link to this paper can be found in Section II of the academic website.

January 2, 2023: The 2023 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2022

December 18, 2022: Today I posted a short note to Section VI of the academic website entitled Exponentiating the Lie algebra of the Lorentz group. In one method, the 4x4 Lorentz transformation matrix (for arbitrary boost and rotation parameters) is obtained by an explict computation of the exponential of the corresponding element of the SO(1,3) Lie algebra. In a second method, the four-vector nature of the spinor product with a free spacetime index is used to to obtain the matrix Λ, which only requires the exponentiation of 2x2 matrices. The two methods are shown to yield the same expression for Λ.

December 1, 2022: Cambridge University Press has announced the availability of a new textbook, entitled From Spinors to Supersymmetry, co-authored by Herbi K. Dreiner, Howard E. Haber and Stephen P. Martin, with an expected publication date of June 2023. Pre-orders are now available. For further details, check out this link .

November 30, 2022: Today, my paper in collaboration with Venus Keus and Rui Santos, entitled P-even, CP-violating Signals in Scalar-Mediated Processes, was pusblished in Physical Review D. A link to this paper can be found in Section II of the academic website.

November 17, 2022: I gave a talk at the IDT-WG3-Phys Open Meeting, which meets once each month to discuss topics assoicated with the ILC and other future e⁺e^- colliders. My talk entitled P-even, CP-violating Signals in Scalar-Mediated Processes is posted to Section VII of the academic website.

October 5, 2022: My contribution to the Proceedings of the 7th Symposium on Prospects in the Physics of Discrete Symmetries, DISCRETE 2020-2021, entitled A natural mechanism for a SM-like Higgs boson in the 2HDM without decoupling, was published today by the Proceedings of Science. The writeup of my plenary talk can be found in Section II of the academic website.

October 4, 2022: My contribution to the Septeber, 2022 CERN EP Newsletter of the EP Department, entitled Higgs Boson Physics - The View Ahead is now available on the arXiv. [PDF]

September 29, 2022: My contribution to the Septeber, 2022 CERN EP Newsletter of the EP Department, entitled Higgs Boson Physics - The View Ahead, was posted to https://ep-news.web.cern.ch/content/higgs-boson-physics-view-ahead. This was one of the contributions to the 10th anniversary of the Higgs boson celebrated this year at CERN.

August 30, 2022: My talk entitled P-even, CP-violating Signals in Scalar-Mediated Processes, given at the Workshop on Multi-Higgs Models at the Instituto Superior Técnico in Lisbon, Portugal, has been posted to Section VII of the academic website.

August 10, 2022: The 2022 edition of the Review of Particle Physics, published today in Progress of Theoretical and Experimental Physics (PTEP), provides a comprehensive review of the field of particle physics and of related areas in cosmology. Topics include Higgs bosons, supersymmetry, big bang nucleosynthesis, probability, statistics, and accelerators and detectors. The latest update of my Supersymmetry Theory review in collaboration with Ben Allanach, which appears in the Review of Particle Physics, can be found in Section III of the academic website.

June 29, 2022: My talk entitled The anapole moment of a charged lepton in softly-broken Supersymmetric QED, given at the SUSY-2022 conference held at the University of Ioannina in Ioannina, Greece, has been posted to Section VII of the academic website.

The talk introduces the properties of the anapole moment of a pointlike charged particle. A one-loop computation of the static anapole moment of the electron (or muon) in softly-broken supersymmetric QED is presented. Some subtelties encountered in extending this result to the full MSSM are discussed.

June 22, 2022: Today, my paper in collaboration with Venus Keus and Rui Santos, entitled P-even, CP-violating Signals in Scalar-Mediated Processes, was posted on the arXiv. A link to this paper can be found in Section II of the academic website.

New sources of neutral scalar-mediated CP violation that arise in extended Higgs sectors can originate in the Yukawa sector or in the structure of the scalar potential. Most treatments in the literature focus on CP-violating Yukawa interactions of neutral scalars, which is an example of P-odd CP violation since it derives from the mixing of two C-even operators of opposite sign P. In contrast, CP-violation arising from the scalar potential is P-even CP-violation, which can be observed by detecting three bosonic processes (suitably chosen) that are incompatible with the presence of a CP-symmetric scalar potential and/or vacuum. The discovery potential of such signals at various future multi-TeV lepton (and γγ) colliders is assessed. The potential for detecting loop-induced P-even, CP-violating phenomena is also considered.

June 13, 2022: Today, Physical Review D posted an erratum to my paper in collaboration with João P. Silva, entitled Exceptional regions of the 2HDM parameter space that appeared a year ago in Physical Review D 103, 115012 (2021). A link to this paper and the erratum can be found in Section II of the academic website.

May 25, 2022: The review entitled Two-component spinor techniques and Feynman rules for quantum field theory and supersymmetry that was published in Physics Reports in 2010 has now been superseded by a new (slightly enhanced) version, which corrects all errors in the published review that have come to the attention of the three authors. This new version is now available on the arXiv, where it appears as version 6 of arXiv:0812.1594 [hep-ph]. Further details can be found in Section III of the academic website.

May 16, 2022: The writeup of my talk, entitled A natural mechanism for a SM-like Higgs boson in the 2HDM without decoupling, which was given at the DISCRETE 2020-2021 conference held in Bergen, Norway on December 3, 2021 has now appeared on the arXiv. [PDF]

February 8, 2022: My presentation to Physics 205 can be found in Section V of the academic website.

February 7, 2022: Stefano Profumo organized Howie-Fest-70 to celebrate my recent retirement and 70th birthday. The zoom event was recorded, and the recording can be found on the event website. A direct link to the MP4 recording can be found at this link.

January 1, 2022: The 2022 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2021

December 8, 2021: Today, I was the (remote) speaker at the NJNU Particle Physics Group weekly seminar series, held at Nanjing Normal University in China. The title of the talk that I gave was Why is the Higgs boson SM-like?. A copy of the slides can be found here: [PDF].

December 3, 2021: My talk entitled A natural mechanism for a SM-like Higgs boson in the 2HDM without decoupling, given at the DISCRETE 2020-2021 conference held in Bergen, Norway has been posted to Section VII of the academic website.

The talk discusses a framework for approximate Higgs alignment that is rspsonsible for the SM-like nature of the observed Higgs boson. A softly-broken symmetry of the bosonic sector of the theory will generate violations of the Higgs alignment limit that can be naturally small. This symmetry can be extended to the Yukawa sector by adding vector-like partners to the SM fermions.

December 1, 2021: The 2021 update of the review articles appearing the Review of Particle Physics by the Particle Data Group (PDG) is now published on the PDG web site. Included among these review articles is the newly revised Supersymmetry, Part I (Theory), which is co-authored by myself and Ben Allanach.

August 30, 2021: My talk entitled Exceptional regions of the 2HDM parameter space, given at the Charged Higgs Online Workshop has been posted to Section VII of the academic website.

August 27, 2021: My lecture entitled Higgs Boson Physics—The View Ahead was the final lecture of the 49th SLAC Summer Institute (SSI 2021). The slides of the lecture have been posted to Section VII of the academic website.

June 10, 2021: Today, my paper in collaboration with João P. Silva, entitled Exceptional regions of the 2HDM parameter space, was published in Physical Review D. A link to this paper can be found in Section II of the academic website.

May 25, 2021: Today, my paper in collaboration with Patrick Draper and Andreas Ekstedt, entitled A natural mechanism for approximate Higgs alignment in the 2HDM, was published in JHEP. A link to this paper can be found in Section II of the academic website.

In this paper, we provide a mechanism for obtaining an approximate Higgs alignment suggested by the LHC Higgs data as a consequence of a softly broken global symmetry of the two-Higgs doublet model (2HDM) Lagrangian. However, this can only be accomplished if the Yukawa sector of the theory is extended. Thus, we propose an extended 2HDM with vector-like top quark partners, where explicit mass terms in the top sector provide the source of the soft symmetry breaking of a generalized CP symmetry. In this way, we can realize approximate Higgs alignment without a significant fine-tuning of the model parameters. The implications of the current LHC bounds on vector-like top quark partners for the success of our proposed scenario are explored.

May 25, 2011: Today, the report of the "Precision SUSY Higgs Mass Calculation Initiative", co-authored with Pietro Slavich et al., was published in the European Physics Journal C. A link to this paper can be found in Section III of the academic website.

Predictions for the Higgs masses are a distinctive feature of supersymmetric extensions of the Standard Model, where they play a crucial role in constraining the parameter space. The "Precision SUSY Higgs Mass Calculation Initiative" (KUTS) was launched in 2014 to provide a forum for discussions between the different groups involved in these efforts. This report aims to present a comprehensive overview of the current status of Higgs-mass calculations in supersymmetric models, to document the many advances that were achieved in recent years and were discussed during the KUTS meetings, and to outline the prospects for future improvements in these calculations.

May 21, 2021: Today, I was the speaker at the SLAC Theory seminar (which is still being held remotely in these pandemic times). The title of the talk that I gave was Adventures in Nima-Land. A copy of the slides can be found here: [PDF]

March 27, 2021: My talk entitled Exceptional regions of the 2HDM parameter space, given at the 5th International Workshop on "Higgs as a Probe of New Physics" Special Edition 2021 (HPNP2021) hosted by Osaka University in Japan and held online, has been posted to Section VII of the academic website. The talk discusses some of the exception features of the softly broken GCP2-symmetric 2HDM scalar potential, with some focus on the Higgs alignment limit and the custodial symmetry limit. Implications of the Yukawa sector are addressed at the end of this talk.

March 10, 2021: Today I posted a short note to Section VI of the academic website entitled Rational approximations to log 2. In this note, a sequence of rational numbers {r_n}, which yield approximations to log 2 that monotonically improve as n increases, is obtained by examining a suitably chosen sequence of integrals.

February 22, 2021: My pedagogical review entitled A tale of three diagonalizations was published today in the International Journal of Modern Physics A. A link to this paper can be found in Section II of the academic website.

In addition to the diagonalization of a normal matrix by a unitary similarity transformation, there are two other types of diagonalization procedures that sometimes arise in quantum theory applications--the singular value decomposition and the Autonne-Takagi factorization. In these notes, each of these diagonalization procedures for the most general 2×2 matrices for which the corresponding diagonalization is possible is explicitly derived and analytical results in each of the three cases are presented.

February 16, 2021: My paper in collaboration with João P. Silva, entitled Exceptional regions of the 2HDM parameter space, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

This paper provides a comprehensive treatment of the exceptional region of the 2HDM parameter space (dubbed the ERPS4) whose scalar potential parameters (using the standard parameterization) satisfy λ₁= λ₂ and λ₆= -λ₇. Such a scalar potential exhibits a generalized CP symmetry, called GCP2, that is softly-broken if m₁₁≠ m₂₂ and/or m₁₂ ≠ 0. Many of the special features of the ERPS4 are highlighted, as well as the properties of even more specialized cases within the ERPS4 framework in which additional constraints on the scalar potential parameters are imposed. Implications for CP violation, the Higgs alignment limit and custodial symmetry are examined.

January 20, 2021: My review entitled Useful relations among the generators in the defining and adjoint representations of SU(N) was published today in SciPost Physics Lecture Notes. A link to this paper can be found in Section II of the academic website.

There are numerous relations among the generators in the defining and adjoint representations of SU(N). These include Casimir operators, formulae for traces of products of generators, etc. Many of these relations are well known and others are more obscure. There are multiple sources for the various identities that are reviewed in this note, but there is no single reference that I am aware of that contains all of them. I have collected many of the relevant identities and assembled them in this short review.

January 19, 2021: My presentation to Physics 205 can be found in Section V of the academic website.

January 1, 2021: The 2021 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2020

December 31, 2020: The report of the "Precision SUSY Higgs Mass Calculation Initiative", co-authored with Pietro Slavich et al., has appeared on the arXiv today. A link to this paper can be found in Section II of the academic website.

November 30, 2020: My paper in collaboration with Patrick Draper and Andreas Ekstedt, entitled A natural mechanism for approximate Higgs alignment in the 2HDM, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

September 10, 2020: A pedagogical note entitled A tale of three diagonalizations was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

August 14, 2020: The 2020 edition of the Review of Particle Physics, published today in Progress of Theoretical and Experimental Physics (PTEP), provides a comprehensive review of the field of particle physics and of related areas in cosmology. Topics include Higgs bosons, supersymmetry, big bang nucleosynthesis, probability, statistics, and accelerators and detectors. The latest update of my Supersymmetry Theory review in collaboration with Ben Allanach, which appears in the Review of Particle Physics, can be found in Section III of the academic website.

August 1, 2020: As of today, I have been recalled to active service for three years (without salary). My new title at the University is Research Professor of Physics. This will permit me to continue my research activities in theoretical particle physics. I look forward to continuing my collaborations both here and abroad (at least via zoom until the day arrives that will allow us to travel once again).

July 1, 2020: I have officially retired from the University of California, Santa Cruz, and henceforth my designation will be Distinguished Professor of Physics Emeritus. Although my teaching duties are now complete, I am still supervising two Ph.D. students, and I will consider the possibility of teaching occasionally in the future if the opportunity presents itself.

May 30, 2020: I have written some notes that provide an explicit computation of the finite part of the Passarino-Veltman function B₀(p²;m₁²,m₂²), which appears in the evaluation of one-loop self-energy diagrams. This note has been posted to Section VI of the academic website.

April 20, 2020: I have posted two sets of notes to Section VI of the academic website. The first note consists of a careful derivation of the expression for the Feynman propagator of scalar field theory, Δ_F(x) in coordinate space (in four spacetime dimensions). Two different treatments are given and various subtleties of the calculations are emphasized. Δ_F(x) is an example of a generalized function (or distribution). In the second note, I provide a practical introduction to generalized functions that is particularly useful in mathematical physics applications, focusing on identifying the most common generalized functions employed in physics and the methods for manipulating them.

March 29, 2020: I have prepared a note entitled, Evaluating the one-loop function arising in h→γγ. This note has been posted to Section VI of the academic website.

March 20, 2020: My paper in collaboration with Rafael Boto, Tiago V. Fernandes, Jorge C. Romao and Joao P. Silva, entitled Basis-independent treatment of the complex 2HDM, was published today in Physical Review D. A link to this paper can be found in Section II of the academic website.

January 22, 2020: My presentation to Physics 205 can be found in Section V of the academic website.

January 6, 2020: My paper in collaboration with Rafael Boto, Tiago V. Fernandes, Jorge C. Romao and Joao P. Silva, entitled Basis-independent treatment of the C2HDM, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

The C2HDM is the most general CP-violating two Higgs doublet model that possesses a softly-broken Z₂ symmetry. To get a better sense of the significance of the C2HDM parameters, we have analyzed this model by employing a basis-independent formalism. Using this method, we have obtained the constraints that enforce the softly-broken Z₂ symmetry. One can then relate the C2HDM parameters to basis-independent quantities up to a two-fold ambiguity, which we then resolve. We have also obtained basis-independent constraints that govern the presence of spontaneous CP violation.

January 1, 2020: The 2020 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2019

December 31, 2019: My review entitled Useful relations among the generators in the defining and adjoint representations of SU(N) was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

December 6, 2019: The 2019 update of the review articles appearing the Review of Particle Physics by the Particle Data Group (PDG) is now published on the PDG web site. More than half of the 119 review articles were revised, many of them very significantly. Included among these review articles is the newly revised Supersymmetry, Part I (Theory), which is now co-authored by myself and Ben Allanach.

September 20, 2019: My talk entitled Future Perspectives (Part 2), given at Higgs Days at Santander 2019 in Santander, Spain, has been posted to Section VII of the academic website.

September 14, 2019: At the Scalars 2019 conference in Warsaw, Poland, I gave two talks. The first talk, entitled Approximate alignment without decoupling in the 2HDM naturally, was given in response to the original invitation to the conference. The second talk, a brief 15 minute presentation that served as the concluding talk of the meeting, was entitled The Future of Particle Physics---A Theorist’s Perspective, and was given due to a request by the main organizer of the conference. Both talks have been posted to Section VII of the academic website.

September 11, 2019: The 1985 Physics Reports review by Howard Haber and Gordon Kane, The Search for Supersymmetry: Probing Physics Beyond the Standard Model, has reached 5,000 citations. It is now in the all-time Top 30 (excluding PDG-RPP) according to INSPIRE HEP.

August 15, 2019: I gave two talks collectively called Higgs Bosons: Past, Present and Future at the Sorak Symposium reminiscence on Particle Physics held at the NakSan Beach Hotel in Yang Yang, South Korea. The first talk was entitled, The incomplete and biased history of the Higgs boson, and the second talk was entitled, Quo Vadis Higgs (or what the current Higgs data is trying to tell us). Both talks have been posted to Section VII of the academic website.

May 27, 2019: My talk entitled Approximate alignment without decoupling in the 2HDM naturally, given at the 7th RISE Collaboration Workshop: NonMinimalHiggs in Helsinki, Finland, has been posted to Section VII of the academic website.

February 18, 2019: My talk entitled Symmetries and Mass Degeneracies in the Scalar Sector, given at HPNP2019 in Osaka, Japan, has been posted to Section VII of the academic website. This talk incorporates a number of new results and understandings as compared to the two previous presentations on the same subject given in September 2018 in Lisbon and in December 2018 in Warsaw.

January 30, 2019: I have written a set of notes entitled A tale of three diagonalizations, which presents an explicit computation of the diagonalization of a 2x2 matrix. This problem often arises in my work, and I have grown tired of continually rederiving these result when needed. So, these results now appear in one place for future reference. In addition to considering the diagonalization of a normal 2x2 matrix by a unitary similarity transformation, these notes also include an analysis of the singular value decomposition of a complex 2x2 matrix and the Autonne-Takagi factorization of a complex symmetric 2x2 matrix. These notes have been posted to Section VI of the academic website.

January 9, 2019: My presentation to Physics 205 can be found in Section V of the academic website.

January 5, 2019: The 2019 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

January 4, 2019: My paper in collaboration with Odd Magne Ogreid, Per Osland and Margarida Nesbitt Rebelo entitled Symmetries and Mass Degeneracies in the Scalar Sector was published today by the Journal of High Energy Physics (JHEP). A link to this paper can be found in Section II of the academic website.

In this work, we explore some aspects of multi-Higgs doublet models that lead to mass degeneracies among some of the physical scalars. Natural scalar mass degeneracies are possible only in the inert two Higgs doublet model (IDM). In the case of three doublets, we introduce and analyze the replicated inert doublet model, which possesses two inert doublets of scalars. We then generalize this model to obtain a scalar potential, which is physically equivalent to a scalar potential first proposed by Ivanov and Silva (IS), with a CP4 symmetry that guarantees the existence of pairwise degenerate scalar states among two of the neutral CP-even, CP-odd and charged Higgs scalars. The properties of the CP4-symmetric IS model that is not invariant under the conventional CP transformation are examined.

News items from 2018

December 31, 2018: Five years after its initial publication, version 4 of The ILC Higgs White paper, which corrects numerous typographical and other minor errors in Chapter 1: Higgs Theory, has been reposted to the arXiv. A link to this paper can be found in Section III of the academic website.

December 10, 2018: My paper in collaboration with Bohdan Grzadkowski, Odd Magne Ogreid and Per Osland entitled Heavy Higgs boson decays in the alignment limit of the 2HDM was published today by the Journal of High Energy Physics (JHEP). A link to this paper can be found in Section II of the academic website.

December 6, 2018: My talk entitled Symmetries and Mass Degeneracies in the Scalar Sector, given at the 5th HARMONIA Warsaw-Lisbon-Catania-Dresden meeting at the OCHOTA campus of the University of Warsaw, in Warsaw, Poland, has been posted to Section VII of the academic website.

October 23, 2018: My paper in collaboration with Miguel P. Bento, Jorge C. Romao and Joao P. Silva, entitled Multi-Higgs doublet models: the Higgs-fermion couplings and their sum rules was published today by the Journal of High Energy Physics (JHEP). A link to this paper can be found in Section II of the academic website.

September 26, 2018: My talk entitled Discussion on Future Colliders, given at the GGI Workshop: "Beyond the Standard Model: Where do we go from here?", at the Galileo Galilei Institute for Theoretical Physics in Arcetri, Florence, Italy, has been posted to Section VII of the academic website.

September 17, 2018: My Viewpoint entitled "Higgs Decay into Bottom Quarks Seen at Last", published online by the American Physical Society in their weekly mailing, "This Week in Physics," describes the significance of the CMS publication, Observation of Higgs Boson Decay to Bottom Quarks, which appeared today in Physical Review Letters. A link to the Viewpoint can be found at the end of Section II of the academic website.

September 4, 2018: My talk entitled Symmetries and Mass Degeneracies in the Scalar Sector, given at the Workshop on Multi-Higgs Models at the Instituto Superior Técnico in Lisbon, Portugal, has been posted to Section VII of the academic website.

August 30, 2018: My talk entitled Beyond Standard Model: Where do we go from here?, given at the GGI Workshop: "Beyond the Standard Model: Where do we go from here?", at the Galileo Galilei Institute for Theoretical Physics in Arcetri, Florence, Italy, has been posted to Section VII of the academic website.

August 28, 2018: My paper in collaboration with O.M. Ogreid, P. Osland and M.N. Rebelo, entitled Symmetries and Mass Degeneracies in the Scalar Sector was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we explore some aspects of CP conserving models with two and three SU(2) scalar doublets that lead to mass degeneracies among some of the physical scalars. Natural scalar mass degeneracies are possible in the inert two Higgs doublet model (IDM). In the case of three doublets, we introduce and analyze the replicated inert doublet model, which possesses two inert doublets of scalars. We then generalize this model to obtain a scalar potential, first proposed by Ivanov and Silva (IS), with a CP4 symmetry that guarantees the existence of pairwise degenerate scalar states among two of the neutral CP-even, CP-odd and charged Higgs scalars. The symmetries of the model permit a term in the IS scalar potential with a complex coefficient that cannot be removed by any redefinition of the scalar fields within the class of Higgs bases (in which case, we say that no real Higgs basis exists and the conventional CP symmetry is absent). Moreover, we demonstrate that it is possible to physically distinguish between the existence or nonexistence of a real Higgs basis despite the fact that no CP-violating observables exist in either case.

August 23, 2018: My paper in collaboration with Miguel P. Bento, Jorge C. Romao and Joao P. Silva, entitled Multi-Higgs doublet models: the Higgs-fermion couplings and their sum rules was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

This is the second of a series of papers that explores the physical parameterization, sum rules and unitarity bounds arising from a non-minimal scalar sector of the Standard Model (SM) that consists of N Higgs doublets. In this paper, we focus on the structure and implication of the Yukawa interactions that couple the N scalar doublets to the SM fermions. We employ the charged Higgs basis introduced in our previous paper. Based on the structure of the Yukawa Lagrangian of the model (and as a consequence of tree-level unitarity), one may deduce numerous sum rules, several of which have not appeared previously in the literature. These sum rules can be used to uncover intimate relations between the structure of the Higgs-fermion couplings and the scalar/gauge couplings. In particular, we demonstrate that the approximate alignment limit imposes significant constraints on the Higgs-fermion couplings of the model.

August 17, 2018: The 60th anniversary edition of the Review of Particle Physics, published in Physical Review D, provides a comprehensive review of the field of particle physics and of related areas in cosmology. Topics include Higgs bosons, supersymmetry, big bang nucleosynthesis, probability, statistics, and accelerators and detectors. My update of the Supersymmetry Theory review, which appears in the Review of Particle Physics, can be found in Section III of the academic website.

August 15, 2018: A written version of my 2016 TASI Lectures entitled Supersymmetric Theories and Models was published in Chapter 6 of TASI 2016: Anticipating the Next Discoveries in Particle Physics, edited by Rouven Essig and Ian Low (World Scientific, Singapore, 2018) pp. 355--499. The written review was a collaborative effort with Laurel Stephenson Haskins. A link to the these lectures can also be found in Section III of the academic website.

August 7, 2018: My paper in collaboration with Bohdan Grzadkowski, Odd Magne Ogreid and Per Osland entitled Heavy Higgs boson decays in the alignment limit of the 2HDM, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this work, we consider the theoretical properties and the phenomenological implications of a generic two Higgs doublet model (2HDM) in the Higgs alignment limit, where the neutral scalar field H₁ coincides with the properties of the Standard Model (SM) Higgs boson. The properties of the two other heavier neutral Higgs scalars, H₂ and H₃, in the alignment limit are tightly constrained and correlated. Observables that could be used to test the alignment scenario at the LHC are defined and discussed. The couplings of the Higgs bosons away from their exact alignment values are determined to leading order, and some consequences are elucidated. Appendices provide a convenient list of 2HDM Feynman rules expressed directly in terms of experimentally observable quantities.

August 6, 2018: My talk entitled The woefully incomplete, unabashedly biased history of the Higgs Boson, given at the 46th SLAC Summer Institute: Standard Model at 50--Successes and Challenges at SLAC in Stanford, CA USA, has been posted to Section VII of the academic website.

June 1, 2018: My talk entitled Beyond the Standard Model Higgs Boson, given at MASS2018: Origin of Mass at the High Energy and Intensity Frontier, at CP³ Origins in Odense, Denmark, has been posted to Section VII of the academic website.

May 22, 2018: My talk entitled Approximate Higgs alignment without decoupling, given at PLANCK 2018: 21th International Conference from the Planck Scale to the Electroweak Scale, in Bonn, Germany, has been posted to Section VII of the academic website.

May 16, 2018: The writeup of my talk given at the 53rd Rencontres de Moriond, QCD and High Energy Interactions Session in La Thuile, Aosta Valley, Italy on March 20, 2018 has now appeared on the arXiv. [PDF]

March 20, 2018: My talk entitled Approximate Higgs alignment without decoupling, given at Rencontres de Moriond: QCD and High Energy Interactions, in La Thuile, Aosta Valley, Italy has been posted to Section VII of the academic website.

February 20, 2018: My talk entitled Mass Degeneracies in Extended Higgs Sectors, given at the TRIUMF Theory Workshop on New Physics and the Higgs at TRIUMF in Vacouver, Canada has been posted to Section VII of the academic website.

February 5, 2018: Notes on the Matrix Exponential and Logarithm have been posted to Section VI of the academic website.

January 23, 2018: My presentation to Physics 205 can be found in Section V of the academic website.

January 5, 2018: The 2018 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2017

December 19, 2017: A written version of my 2016 TASI Lectures entitled Supersymmetric Theories and Models was posted today as a preprint on the arXiv, thanks to a collaborative effort with my co-author Laurel Stephenson Haskins. A link to the written version of these lectures can be found in Section II of the academic website.

November 30, 2017: My talk entitled Replicating the Higgs Doublet, given at Scalars 2017 at the Unversity of Warsaw in Warsaw, Poland, has been posted to Section VII of the academic website.

November 15, 2017: My paper in collaboration with Miguel Bento, J.C. Romao and Joao Silva entitled Multi-Higgs doublet models: physical parametrization, sum rules and unitarity bounds was published in the Journal of High Energy Physics (JHEP). A link to this paper can be found in Section II of the academic website.

In this work, we examine the structure of a Higgs sector consisting of N Higgs doublets. We demonstrate the good features of the so-called charged Higgs basis, which allow us to explicitly identify the physical parameters of the model. We also derive simple forms for the couplings of the Higgs bosons and vector bosons for and some of the Goldstone boson interactions. These results are applied in the derivation of Higgs coupling sum rules and tree-level unitarity bounds that restrict the size of the quartic scalar couplings.

November 6, 2017: My paper in collaboration with Sven Heinemeyer and Tim Stefaniak, entitled The Impact of Two-Loop Effects on the Scenario of MSSM Higgs Alignment without Decoupling, was published in European Physical Journal C. A link to this paper can be found in Section II of the academic website.

In this work, we assesed the impact of the leading two-loop O(α_s h_t²) corrections to the Higgs alignment condition in the MSSM. These corrections are sizable and important in the relevant regions of parameter space and furthermore give rise to solutions of the alignment condition that are not present in the approximate one-loop description. The implications for phenomenologically viable regions of the MSSM parameter space were considered.

September 29, 2017: My talk entitled Alignment in Models of Extended Higgs Sectors, given at the NTU workshop: "Energy Frontier in Particle Physics: LHC and Future Colliders" at National Taiwan University in Taipei, Taiwan, has been posted to Section VII of the academic website.

September 12, 2017: My talk entitled Non-minimal Higgs sectors, given at the GGI Workshop: "Collider Physics and the Cosmos" at the Galileo Galilei Institute for Theoretical Physics in Arcetri, Florence, Italy, has been posted to Section VII of the academic website.

August 31, 2017: My paper in collaboration with Miguel Bento, J.C. Romao and Joao Silva entitled Multi-Higgs doublet models: physical parametrization, sum rules and unitarity bounds, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this work, we examine the structure of a Higgs sector consisting of N Higgs doublets. We show that the interactions of the gauge bosons with the physical Higgs scalars and the Goldstone bosons are determined by an N x 2N matrix. This matrix depends on (N-1)(2N-1) real parameters that are associated with the mixing of the neutral Higgs fields in the so-called charged Higgs basis. Among these parameters, N-1 are unphysical (and can be removed by rephasing the physical charged Higgs fields), and the remaining 2(N-1)² parameters are physical. We also derive a particularly simple form for the cubic interactions and some of the quartic interactions of the Goldstone bosons with the physical Higgs scalars. These results are applied in the derivation of Higgs coupling sum rules and tree-level unitarity bounds that restrict the size of the quartic scalar couplings.

August 15, 2017: My paper in collaboration with Sven Heinemeyer and Tim Stefaniak, entitled The Impact of Two-Loop Effects on the Scenario of MSSM Higgs Alignment without Decoupling, was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In the Higgs sector of the MSSM, alignment without decoupling is possible only in a parameter regime where there is an accidental cancellation of tree-level and radiative loop-level effects. In this paper we assess the impact of the leading two-loop O(α_s h_t²) corrections to the Higgs alignment condition in the MSSM. These corrections are sizable and important in the relevant regions of parameter space and furthermore give rise to solutions of the alignment condition that are not present in the approximate one-loop description. We provide a comprehensive numerical comparison of the alignment condition obtained in the approximate one-loop and two-loop approximations, and discuss its implications for phenomenologically viable regions of the MSSM parameter space.

July 16, 2017: In response to a question posed by Joao P. Silva, I have shown that an arbitrary 2n x 2n real orthogonal antisymmetric matrix can be parameterized by n(n−1) continuous angular parameters, and I ave provide an algorithm for constructing the general form for such a matrix in a set of notes entitled Parameterization of real orthogonal antisymmetric matrices. These notes have been posted to Section VI of the academic website.

June 23, 2017: My paper in collaboration with Stefania Gori and Edward Santos entitled High scale flavor alignment in two-Higgs doublet models and its phenomenology was published in the Journal of High Energy Physics (JHEP). A link to this paper can be found in Section II of the academic website.

In this paper, we considered the two Higgs doublet model (2HDM) in which flavor alignment is imposed at the Planck scale, resulting in the generation of Higgs-mediated FCNCs at the electroweak scale via renormalization group running. Using the current experimental bounds on flavor changing observables, constraints were derived on the aligned 2HDM parameter space, and its implications for Higgs boson phenomenology were analyzed.

June 15, 2017: A set of notes entitled Useful relations among the generators in the defining and adjoint representations of SU(N) has been posted to Section VI of the academic website.

June 9, 2017: In the Championship game vs. the Bad News Brewskis, Re-Entry claimed the Championship T-shirts with a riveting 15--11 victory. An eight run second inning provided a big lead early, and Re-Entry was able to withstand eight Bad News Brewskis runs over the last three innings, as their comeback fell short by four runs. With this win, Re-Entry claims a sweep with two straight softball championships over the 2016--2017 academic year. For further details, check out the UCSC Coed Softball Re-Entry Team Webpage.

May 28, 2017: My talk entitled In search of natural Higgs alignment without decoupling in the 2HDM, given at the 2nd HARMONIA Warsaw-Lisbon-Catania-Dresden meeting at the University of Warsaw in Warsaw, Poland, has been posted to Section VII of the academic website.

May 22, 2017: My talk entitled Alignment in extended Higgs models, given at PLANCK 2017 in Warsaw, Poland, has been posted to Section VII of the academic website.

March 20, 2017: My paper in collaboration with Stefania Gori and Edward Santos entitled High scale flavor alignment in two-Higgs doublet models and its phenomenology was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

One way to suppress Higgs-mediated flavor changing neutral currents (FCNCs) in the two Higgs doublet model (2HDM) is to demand that all Yukawa coupling matrices are diagonal when expressed in the basis of mass-eigenstate fermion fields. In this paper, we examine the 2HDM in which the flavor alignment condition is imposed at a very high energy scale. Renormalization group evolution then yields small neutral Higgs-mediated FCNCs at the electroweak scale, which can be constrained by experimental bounds on flavor changing observables. In the favored parameter region, the implications for Higgs boson phenomenology are analyzed.

March 6, 2017: My talk entitled High scale flavor-aligned 2HDM, given at the 3rd RISE Collaboration Meeting: NonMinimalHiggs in Toyama, Japan, has been posted to Section VII of the academic website.

March 1, 2017: My talk entitled A Theorist's Outlook for Higgs physics beyond the Standard Model, given at HPNP2017 in Toyama, Japan, has been posted to Section VII of the academic website.

February 3, 2017: My paper in collaboration with Philip Bechtle, Sven Heinemeyer, Tim Stefaniak, Oscar Stål, Georg Weiglein, and Lisa Zeune entitled The Light and Heavy Higgs Interpretation of the MSSM was published on my birthday in European Physical Journal C. A link to this paper can be found in Section II of the academic website.

In this paper, various MSSM interpretations of the Higgs signal at 125 GeV, in which the observed Higgs boson is identified with either the lightest or heaviest CP-even Higgs scalar of the MSSM. Regions close to the alignment limit without decoupling are still allowed and offer good prospects for upcoming LHC searches and searches at future colliders.

January 30, 2017: At the Maria Goeppert Mayer Award, Sakurai Prize Session of the April APS Meeting 2017, I gave a talk entitled Beyond the Standard Model Higgs Boson. The slides from the talk has been posted to Section VII of the academic website.

January 29, 2017: The APS prize and award winners were recognized at a ceremony held at the April APS Meeting 2017. The co-recipients of the J.J. Sakurai Prize for Theoretical Particle Physics received their awards during the APS Prizes and Awards Ceremonial Session.

January 23, 2017: My presentation to Physics 205 can be found in Section V of the academic website.

January 10, 2017: The official writeup of my talk given at the Sixth International Workshop on the Prospects for Charged Higgs Discovery at Colliders (CHARGED 2016) in Uppsala, Sweden on October 6, 2016 has now appeared on the arXiv. [Postscript | PDF]

January 2, 2017: The 2017 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2016

December 16, 2016: My talk entitled High scale flavor alignment in the 2HDM and its phenomenology, given at the Helsinki Higgs Forum in Helsinki, Finland, has been posted to Section VII of the academic website.

November 18, 2016: After a season of rainouts and forfeits, Team Re-Entry finally got to play a meaningful game, as the two undefeated teams of the UCSC Coed Softball league met in the Championship game. Re-Entry dominated "Where my pitches at" with a convincing 15--2 victory in a game that was called early due to the impending darkness. The three year drought is now over, as Re-Entry claimed its eleventh championship since 1996. For further details, check out the UCSC Coed Softball Re-Entry Team Webpage.

November 17, 2016: Q&A: What more can we learn about the Higgs? Four physicists (myself included) discuss Higgs boson research since the discovery with Angela Anderson of Symmetry Magazine (a joint Fermilab/SLAC publication).

November 11, 2016: My talk entitled SUSY and the alignment limit, given at Higgs Couplings 2016 at SLAC has been posted to Section VII of the academic website.

October 10, 2016: The American Physical Society has announced that Gordon Kane, Howard Haber, John Gunion and Sally Dawson have been awarded the 2017 J.J. Sakurai Prize for Theoretical Particle Physics. Further details can be found at https://www.aps.org/units/dpf/awards/sakurai.cfm and at the UC Santa Cruz Newscenter.

October 6, 2016: My talk entitled Future Higgs Studies: A Theorist's Outlook, given at the Sixth International Workshop on the Prospects for Charged Higgs Discovery at Colliders (CHARGED 2016) in Uppsala, Sweden has been posted to Section VII of the academic website.

October 4, 2016: The 2016 edition of the Review of Particle Physics is now available on the Web. Included are the Summary Tables, Particle Listings, pdgLive and Review articles, including my updated review of Supersymmety Theory. The Review of Particle Physics is now published in the October, 2016 issue of Chinese Physics C. A hard copy of the review can be obtained here. [PDF]

September 26, 2016: An erratum to my paper in collaboration with Pedro Ferreira and Edward Santos, entitled Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale, was published today in Physical Review D. A link to the published erratum can be found in Section II of the academic website.

September 20, 2016: My talk entitled Alignment without decoupling in the MSSM, given at Higgs Days at Santander 2016 in Santander, Spain has been posted to Section VII of the academic website.

September 6, 2016: My talk entitled Flavor violation via Planck scale alignment in the 2HDM, given at the Workshop on Multi-Higgs Models in Lisbon, Portugal, has been posted to Section VII of the academic website.

September 2, 2016: My talk entitled Higgs Hunting 2016 Theory Summary Talk, given at Higgs Hunting 2016 in Paris, France, has been posted to Section VII of the academic website.

August 3, 2016: My paper in collaboration with Philip Bechtle, Sven Heinemeyer, Tim Stefaniak, Oscar Stål, Georg Weiglein, and Lisa Zeune entitled The Light and Heavy Higgs Interpretation of the MSSM was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we performed a parameter scan of the eight-parameter pMSSM taking into account the experimental Higgs boson results from Run I of the LHC as well as additional low-energy observables. We investigated various MSSM interpretations of the Higgs signal at 125 GeV, in which the observed Higgs boson is identified with either the lightest or heaviest CP-even Higgs scalar of the MSSM. We identified regions close to the alignment limit without decoupling, in which the other Higgs scalars of the MSSM can also be light, offering good prospects for upcoming LHC searches and searches at future colliders.

July 26, 2016: My paper in collaboration with Michael Dine, Patrick Draper and Laurel Stephenson Haskins entitled Perturbation Theory in Supersymmetric QED: Infrared Divergences and Gauge Invariance was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we investigated some aspects of the perturbation theory in N=1 supersymmetric gauge theories with massive charged matter. In general gauges, infrared divergences and nonlocal behavior arise in 1PI diagrams, associated with a 1/k⁴ term in the propagator for the vector superfield. We have examined this structure in supersymmetric QED. The IR divergences are gauge-dependent and must cancel in physical quantities like the electron pole mass. However, this cancellation takes place in a nontrivial way, amounting to a reorganization of the perturbative series from powers of e² to powers of e (where e is the γe⁺e^- coupling constant).

July 6, 2016: My talk entitled Extended Higgs sectors and the alignment limit, given at the 24rd International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2016) has been posted to Section VII of the academic website.

July 1, 2016: Today I gave the last of three lectures entitled SM and SUSY Higgs at pre-SUSY 2016 in Melbourne, Australia. Links to the PDF slides of the three lectures can be found in Section VII of the academic website.

June 21, 2016: My paper in collaboration with Patrick Draper and Josh Ruderman entitled Partially Natural Two Higgs Doublet Models was published today in the Journal of High Energy Physics (JHEP). This paper examines the number of independent fine-tunings required in the two Higgs doublet model (2HDM) and demonstrates under what circumstances the number of fine-tunings of the 2HDM can be reduced to the one fine tuning that sets the electroweak scale in the Standard Model. A link to this paper can be found in Section II of the academic website.

June 15, 2016: Today I gave the last of four lectures entitled Supersymmetric Theory and Models at the 2016 Theoretical Advanced Study Institute (TASI 2016) in Boulder, CO. Links to the PDF slides of the four lectures can be found in Section VII of the academic website.

June 6, 2016: The erratum to my paper in collaboration with Oscal Stål entitled New LHC Benchmarks for the CP-conserving Two-Higgs-Doublet Model was published today in European Physical Journal C. A link to this erratum can be found in Section II of the academic website.

June 3, 2016: The Re-Entry softball team met up with the Might Shmucks in the Championship game of the UCSC Friday late afternoon coed softball league. Re-Entry came back from an eight run deficit to take a one run lead in the penultimate inning. After giving up two runs in the top of the last inning, Re-Entry attempted one last comeback. But, with the tying and winning runs on base, Re-Entry was unable to produce the game winning hit. The result was a one run loss in the Championship game for the third time since the fall of 2012. For further details, check out the UCSC Coed Softball Re-Entry Team Webpage.

May 17, 2016: A corrected version of my paper in collaboration with Oscal Stål entitled New LHC Benchmarks for the CP-conserving Two-Higgs-Doublet Model was uploaded today to the arXiv. A link to this paper can be found in Section II of the academic website. An official erratum will be published soon in the European Physics Journal C.

May 12, 2016: My paper in collaboration with Patrick Draper and Josh Ruderman entitled Partially Natural Two Higgs Doublet Models was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we consider the implications of a discovery of new light fundamental scalars other than the Standard Model Higgs boson, under the assumption that the electroweak symmetry breaking scale is fine-tuned (perhaps as a result of selection effects). In this latter case, the common wisdom is that all additional elementary scalars must be heavy. We discuss counterexamples where the Higgs boson is light because of fine-tuning, and a second scalar doublet is light because a discrete symmetry relates its mass to the mass of the Standard Model Higgs boson. Our examples require new vectorlike fermions at the electroweak scale, and the models possess a rich electroweak vacuum structure.

April 18, 2016: My talk entitled Revisiting the 2012 Higgs Wishlist, given at the KITP Workshop on Experimental Challenges for the LHC Run II has been posted to Section VII of the academic website.

February 29, 2016: My paper in collaboration with Jérémy Bernon, John F. Gunion, Yun Jiang and Sabine Kraml entitled Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models. II.: m_H=125 GeV was published today in Physical Review D. In this paper, we examine the theoretical structure and the phenomenological implications of the alignment regime of the 2HDM (with and without decoupling) where the couplings of the heavier of the two CP-even Higgs scalars are nearly indistinguishable from those of the Standard Model (SM) Higgs boson. Implications for Run 2 at the LHC, including expectations for observing the non-SM-like scalar states, are considered. A link to this paper can be found in Section II of the academic website.

February 19, 2016: The Particle Data Group (PDG) announces that updated PDG review articles for the 2016 edition of the Review of Particle Physics are now available at http://pdg.lbl.gov/. In particular, check out my updated review of Supersymmetry, Part I (Theory).

February 17, 2016: My paper, in collaboration with Marcela Carena, Ian Low, Nausheen Shah and Carlos Wagner, entitled Alignment limit of the NMSSM Higgs sector was published today in Physical Review D. In this paper, we identify the Higgs alignment region of the NMSSM parameter space where the observed Higgs boson is predicted to have SM-like properties. The alignment limit in the NMSSM leads to a well defined spectrum in the Higgs and Higgsino sectors, and yields a rich and interesting Higgs boson phenomenology that can be tested at the LHC. A link to this paper can be found in Section II of the academic website.

January 11, 2016: My presentation to Physics 205 can be found in Section V of the academic website.

January 3, 2016: The 2016 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not intended to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2015

December 31, 2015: My three year term as Secretary-Treasurer of the Division of Particles and Fields of the American Physical Society has now come to an end. Best of luck to my successor, Kate Scholberg!

December 6, 2015: The 1st RISE Collaboration Meeting: NonMinimalHiggs took place on December 6--8, 2015 as an adjunct to the Scalars 2015 Conference held at the University of Warsaw. I presented by vidyo link the Santa Cruz node of the RISE Collaboration [PDF]

November 13, 2015: My paper in collaboration with Jérémy Bernon, John F. Gunion, Yun Jiang and Sabine Kraml entitled Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models: Part 2: m_H=125 GeV was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we consider CP-conserving Two-Higgs-Doublet Models (2HDMs) of Type I and Type II near the alignment limit in which the heavier of the two CP-even Higgs bosons, H, is the SM-like state of mass 125 GeV. We review the theoretical structure and analyze the phenomenological implications of this particular realization of the alignment limit, which contains at least one (and perhaps more than one) scalar Higgs state with a mass below 125 GeV. For the numerical analysis, all relevant pre-LHC constraints, constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for additional Higgs-like states are employed, and the implications for Run 2 at the LHC are elucidated.

November 2, 2015: My paper in collaboration with Marcela Carena, Ian Low, Nausheen Shah and Carlos Wagner On the Alignment Limit of the NMSSM Higgs Sector was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, an attractive region of the NMSSM parameter space is identified in which the alignment limit is realized and the observed Higgs boson is predicted to have SM-like properties. Analytic expressions for the alignment conditions are derived and are shown to point toward a more natural region of parameter space for electroweak symmetry breaking. Moreover, the alignment limit in the NMSSM leads to a well defined spectrum in the Higgs and Higgsino sectors, and yields a rich and interesting Higgs boson phenomenology that can be tested at the LHC.

October 15, 2015: My paper in collaboration with Oscal Stål entitled New LHC Benchmarks for the CP-conserving Two-Higgs-Doublet Model was published today in European Physical Journal C. This paper presents a strategy to study the parameter space of the CP-conserving, two-Higgs-doublet Model (2HDM) with Type I or II Yukawa couplings. Benchmark points, lines and planes are established by specifying the observed Higgs boson mass and its coupling strength to vector boson pairs, the mass of the second CP-even Higgs boson, the ratio of neutral Higgs vevs, and three additional dimensionless parameters. Our benchmark scenarios capture different aspects of non-standard Higgs phenomenology that are of interest for future LHC Higgs searches. A link to this paper can be found in Section II of the academic website.

October 6, 2015: My paper in collaboration with Jérémy Bernon, John F. Gunion, Yun Jiang and Sabine Kraml entitled Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models: m_h=125 GeV was published today in Physical Review D. In this paper, we examine the theoretical structure and the phenomenological implications of the alignment regime of the 2HDM (with and without decoupling) where the couplings of the lighter of the two CP-even Higgs scalars are nearly indistinguishable from those of the Standard Model (SM) Higgs boson. Implications for Run 2 at the LHC, including expectations for observing the non-SM-like scalar states, are considered. A link to this paper can be found in Section II of the academic website.

August 24, 2015: My talk entitled Partially Natural Two Higgs Doublet Models, given at the 23rd International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2015) has been posted to Section VII of the academic website.

August 3, 2015: My paper, in collaboration with Pedro Ferreira and Edward Santos, entitled Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale, was published today in Physical Review D. This paper examines the constraints on the two Higgs doublet model (2HDM) due to the stability of the scalar potential and absence of Landau poles at energy scales below the Planck scale. The parameter regimes of the 2HDM with a 125 GeV SM-like Higgs boson that are stable and perturbative up to the Planck scale yield significant constraints on the heavy scalar spectrum. A link to this paper can be found in Section II of the academic website.

July 16, 2015: My paper in collaboration with Oscal Stål entitled New LHC Benchmarks for the CP-conserving Two-Higgs-Doublet Model was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we introduce a strategy to study the parameter space of the general, CP-conserving, two-Higgs-doublet Model (2HDM) with a softly broken Z₂-symmetry by means of a new hybrid basis of parameters consisting of the measured values of the mass of the observed Higgs boson and its coupling strength to vector boson pairs, the mass of the second CP-even Higgs boson, the ratio of neutral Higgs vevs, and three additional dimensionless parameters. We use these input parameters to perform numerical scans of the 2HDM parameter space, surveying the available parameter regions and analyzing the model constraints. Using these results, we define a number of benchmark scenarios that capture different aspects of non-standard Higgs phenomenology that are of interest for future LHC Higgs searches.

July 6, 2015: My paper in collaboration with Jérémy Bernon, John F. Gunion, Yun Jiang and Sabine Kraml entitled Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models:Part 1: m_h=125 GeV was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we focus on the alignment regime of the 2HDM parameter regime where the couplings of the lighter of the two CP-even Higgs scalars are nearly indistinguishable from those of the Standard Model (SM) Higgs boson. We review the theoretical structure and analyze the phenomenological implications of the alignment limit without decoupling, in which the masses of the non-SM-like Higgs scalars are not significantly larger than the SM-like Higgs boson. For the numerical analysis, we perform scans of the 2HDM parameter space, taking into account all relevant pre-LHC constraints, the latest constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for other Higgs-like states. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are considered.

July 1, 2015: An expanded version of the June 23 talk entitled, LHC Benchmarks for the CP-conserving Two-Higgs-Doublet Model was presented at an LIP seminar at the Laboratorio de Instrumentacao e Fisica Experimental de Particulas in Lisbon, Portugal. The slides from the seminar have been posted to Section VII of the academic website.

June 23, 2015: I gave a talk via vidyo to the 2HDM subgroup of the LHC Higgs Cross Section Working Group at CERN entitled LHC Benchmarks for the CP-conserving 2HDM, which has been posted to Section VII of the academic website.

June 10, 2015: Version 2 of the paper entitled Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale was re-posted today on the arXiv. The revised version adds a number of references, corrects some typographical errors, and adds a clarifying footnote. A link to the revised paper can be found in Section II of the academic website.

June 9, 2015: My Ph.D. student Laura Fava passed her Ph.D. thesis defense. Congratulations Laura!!!

June 7, 2015: After many years of toil, we get to celebrate the new Ph.D.'s.

May 29, 2015: Team Re-Entry's attempt to reclaim the UCSC Intramurals Coed Softball Championship just falls short when the umpires rule that the dramatic walk-off game winning two run homerun by A.J. was foul. Unable to overcome that unfathomable call, instead of celebrating the 5--4 victory, Re-Entry was on the losing end of a 4--3 heartbreaking loss to the Master Batters. For more details, click on this link.

May 28, 2015: My Ph.D. student Eddie Santos passed his Ph.D. thesis defense. Congratulations Eddie!!!

May 20, 2015: My talk entitled The Alignment Limit of the MSSM Higgs sector--the Impact of Radiative Corrections, given at the Third KUTS Workshop at LPTHE in Paris, France has been posted to Section VII of the academic website.

May 18, 2015: My paper in collaboration with Pedro Ferreira and Edward Santos entitled Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

In this paper, we examined the constraints on the two Higgs doublet model (2HDM) due to the stability of the scalar potential and absence of Landau poles at energy scales below the Planck scale. Using basis independent techniques, we exhibited regimes of the 2HDM parameter space with a 125 GeV SM-like Higgs boson that is stable and perturbative up to the Planck scale. Implications for the heavy scalar spectrum were presented.

April 20, 2015: My talk entitled Partially Natural Two Higgs Doublet Models, given at the 4th MCTP Spring Symposium on Higgs Boson Physics in the Standard Model and Beyond has been posted to Section VII of the academic website.

March 10, 2015: The speaker list for the SCIPP Reunion Theory Symposium is now set. The Theory Symposium will take place on UCSC campus in ISB 102 from 2--6 pm on Friday April 24, 2015. For further details, check out the SCIPP Theory Symposium webpage.

March 6, 2015: Higgs boson a la carte? Check out the article in Fermilab Today that reports on my recent paper with Marcela Carena, Ian Low, Nausheen Shah and Carlos Wagner that was published last month in Physical Review D.

February 14, 2015: My talk entitled Constraints on the alignment limit of the MSSM Higgs sector, given at the The 2nd Toyama International Workshop on "Higgs as a Probe of New Physics 2015" (HPNP2015) has been posted to Section VII of the academic website. This talk is a shorter version of the seminar that I gave in January at the Lawrence Berkeley National Laboratory (with a few minor updates).

February 3, 2015: My paper, in collaboration with Marcela Carena, Ian Low, Nausheen Shah and Carlos Wagner, entitled Complementarity between nonstandard Higgs boson searches and precision Higgs boson measurements in the MSSM was published on my birthday in Physical Review D. This paper discusses the viability of alignment without decoupling in the MSSM Higgs sector. Approximate alignment can be achieved via an accidental cancellation between tree-level and loop-level contributions. However precision Higgs data combined with the LHC search for heavier Higgs states that decay into τ⁺τ^- already places strong constraints on this scenario. A link to this paper can be found in Section II of the academic website.

January 28, 2015: I gave a talk at Lawrence Berkeley National Laboratory entitled Constraints on the alignment limit of the MSSM Higgs sector. The slides from the talk can be found here: [PDF]

January 18, 2015: An expanded version of my notes entitled Notes on antisymmetric matrices and the pfaffian have been posted to Section VI of the academic website.

January 12, 2015: My presentation to Physics 205 can be found in Section V of the academic website.

January 7, 2015: The 2015 Particle Physics conference schedule has been posted to Section VIII of the academic website. Although not meant to be comprehensive, it covers many conferences that overlap with my research interests.

News items from 2014

October 31, 2014: Version 2 of the paper entitled Complementarity Between Non-Standard Higgs Searches and Precision Higgs Measurements in the MSSM was re-posted today on the arXiv. The revised version adds a short discussion on possible symmetries that may govern the alignment limit of the two-Higgs doublet model, in contrast to the case of the MSSM where the alignment limit, if present, is the result of an accidental cancellation of tree-level and loop-level contributions. A link to the revised paper can be found in Section II of the academic website.

October 29, 2014: The San Francisco Giants win the World Series in the deciding Game 7, with a 3--2 win over the Kansas City Royals. What an epic game! Three hours of high drama and a once in a lifetime pitching performance by Madison Bumgarner to earn a five inning save.

October 21, 2014: My paper in collaboration with Marcela Carena, Ian Low, Nausheen Shah and Carlos Wagner entitled Complementarity Between Non-Standard Higgs Searches and Precision Higgs Measurements in the MSSM was posted today on the arXiv. A link to this paper in Section II of the academic website.

This paper examines the conventional wisdom that the constraints of the precision Higgs data implies that additional non Standard Model (SM)--like Higgs bosons of the MSSM should be heavy, with masses larger than about 400 GeV. We demonstrate that this conclusion does not hold when the theory approaches the conditions for "alignment independent of decoupling", where the lightest CP-even Higgs boson has SM-like tree-level couplings to fermions and gauge bosons, independently of the non-standard Higgs boson masses. We find that precision Higgs measurements and direct searches are complementary, and may soon be able to probe the region of non-SM-like Higgs boson with masses below the top quark pair mass threshold of 350 GeV and low to moderate values of tan β.

September 25, 2014: My talk entitled Constraints on the alignment limit of the MSSM Higgs sector, given at the IFT Program on Physics Challenges in the face of LHC-14 at the Instituto de Fisica Teórica in Madrid, Spain has been posted to Section VII of the academic website. This talk updates the one of the same title given in Lisbon four weeks earlier.

September 23, 2014: My talk entitled Motivations for a stable scalar in an extended Higgs sector, given at the IFT Program on Physics Challenges in the face of LHC-14 at the Instituto de Fisica Teórica in Madrid, Spain has been posted to Section VII of the academic website.

September 9, 2014: My talk entitled 2HDM Benchmarks--Theoretical Framework, given at Higgs Days at Santander 2014 has been posted to Section VII of the academic website.

September 3, 2014: The 2014 edition of the Review of Particle Physics is now available on the Web. Included are the Summary Tables, Particle Listings, pdgLive and Review articles, including my updated review of Supersymmety Theory. The Review of Particle Physics is now published in the August, 2014 issue of Chinese Physics C. A hard copy of the review can be obtained here. [PDF]

September 2, 2014: My talk entitled Constraints on the alignment limit of the MSSM Higgs sector, given at the Workshop on Multi-Higgs Models in Lisbon, Portugal has been posted to Section VII of the academic website.

July 22, 2014: My talk entitled Can the Hbb coupling be equal in magnitude to its SM value but opposite in sign?, given at the SUSY 2014 Conference in Manchester, UK, has been posted to Section VII of the academic website.

June 13, 2014: I gave a talk via vidyo to the Workshop of the LHC Higgs Cross Section Working Group at CERN entitled 2HDM---Report on recent activities, which has been posted to Section VII of the academic website.

June 6, 2014: Team Re-Entry's attempt to win its third consecutive UCSC Intramurals Coed Softball Championship was thwarted by Team Musashi. For more details on the 18--12 loss in the Championship game, click on this link.

June 3, 2014: My paper in collaboration with Pedro Ferreira, Rui Santos and John Gunion, entitled Probing wrong-sign Yukawa couplings at the LHC and a future linear collider was published today in Physical Review D. This paper discusses the possibility that all couplings of the recently discovered Higgs boson are close to their Standard Model values in magnitude, but the overall sign of Higgs coupling to down-type fermions is reversed as compared to its Standard Model value. Prospects for detecting this wrong-sign Yukawa coupling at the LHC and ILC are investigated. A link to this paper can be found in Section II of the academic website.

May 15, 2014: I gave a talk to the Higgs/Electroweak Symmetry Breaking and Beyond Standard Model/Cosmology joint session at the AWLC14 meeting at Fermilab entitled Probing wrong-sign Yukawa couplings, which has been posted to Section VII of the academic website.

May 12, 2014: I gave a plenary talk at the AWLC14 meeting at Fermilab entitled Higgs Physics, which has been posted to Section VII of the academic website.

April 11, 2014: A short talk entitled Some Issues for Precision Higgs Mass Computations, given via Vidyo to the KUTS Workshop (I) at the Max-Planck-Institut für Physik in Munich, has been posted to Section VII of the academic website.

March 28, 2014: My talk entitled Precision Higgs and Future Colliders given at Gunion Fest, held at the University of California, Davis, has been posted to Section VII of the academic website. Follwoing the evening banquet, I gave the after dinner talk entitled Celebating more than 30 years of friendship and collaboration, which can be found here: [PDF | Powerpoint]

March 27, 2014: Version 2 of the paper entitled Probing wrong-sign Yukawa couplings at the LHC and a future linear collider was re-posted today on the arXiv. The revised version includes a new Appendix B, which examines whether there exist regions of the MSSM Higgs parameter space in which the hbb coupling is equal in magnitude to its Standard Model value but opposite in sign. A link to this paper can be found in Section II of the academic website.

March 20, 2014: My paper in collaboration with Pedro Ferreira, Jack Gunion and Rui Santos entitled Probing wrong-sign Yukawa couplings at the LHC and a future linear collider was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

This paper discusses the possibility that all couplings of the recently discovered Higgs boson are close to their Standard Model values in magnitude, but the overall sign of Higgs coupling to down-type fermions is reversed as compared to its Standard Model value. The possibility of achieving this in a Type-II two Higgs doublet model is demonstrated, and the prospects for detecting this wrong-sign Yukawa coupling at the LHC and ILC are investigated.

March 14, 2014: My talk at the biannual Bay Area Particle Theory Seminar, entitled Decoupling and Alignment in Light of the Higgs data, can be found here: [PDF]. It has also been posted to Section VII of the academic website.

March 9, 2014: I was interviewed on KUSP radio in Santa Cruz by Robert Pollie for his weekly radio program entitled The 7th Avenue Project: Thinking Persons' Radio. The interview focused on the Higgs boson and can be found here: [HTML | mp3]

February 11, 2014: Howard Haber and Abraham Seiden delivered the 48th annual UCSC Faculty Research Lecture, entitled The Higgs Boson Unleashed. For further information, see this news link. The slides can be found here: [PDF | Powerpoint] (these are very large files of 44 MB and 63 MB respectively).

January 13, 2014: My presentation to Physics 205 can be found in Section V of the academic website.

January 8, 2014: The revised version of the Higgs Working Group Report of the Snowmass 2013 Community Planning Study was posted to the arXiv. The authors of the ILC Higgs White paper have now been included as co-authors of the Higgs Working Group report. [PDF]

January 3, 2014: Better late than never. The official writeup of my talk given at the 2013 Toyama International Workshop on Higgs as a Probe of New Physics (HPNP2013) on February 14, 2013 has finally appeared (with a new title) on the arXiv [Postscript | PDF] and can be found in the Proceedings of the Workshop.

News items from 2013

December 31, 2013: The third and final revised version of the ILC Higgs White Paper has been re-posted to the arXiv [PDF].

December 25, 2013: Good Times, a weekly Santa Cruz newspaper, reports on UC Santa Cruz's top scientific breakthroughs of 2013. One of the research stories, entitled "All Hail the Higgs Boson" describes the role of SCIPP physicists in the discovery of the Higgs boson and includes quotes from yours truly. [HTML]

December 19, 2013: The 2013 partial update for the 2014 edition of the "Reviews, Tables, Plots" section of the Review of Particle Physics by the Particle Data Group is now available here. This includes the 2013 update of my review, Supersymmetry, Part I (Theory).

December 6, 2013: Team Re-Entry wins its second consecutive UCSC Intramurals Coed Softball Championship in dominant fashion with a 26--1 victory over Team Jopo. For more details click on this link.

November 15, 2013: I gave the summary talk for the Higgs/EWSB Working Group at the International Linear Collider meeting, LCWS-2013, which was held in Japan. This talk has been posted to Section VII of the academic website.

November 12, 2013: My talk entitled The Higgs Boson: Past, Present and Future given at the 2013 Inter-Acadamy Seoul Science Forum, held in Seoul, South Korea has been posted to Section VII of the academic website.

October 23, 2013: A revised version of the ILC Higgs White Paper has been re-posted to the arXiv [PDF].

October 18, 2013: Howard Haber and Abraham Seiden have been chosen as the 2013 UCSC Founders Day Dinner Faculty Research Lecturers for their highly distinguished research records and for playing major roles in the successful search for the Higgs boson! [HTML]

October 2, 2013: The ILC Higgs White Paper, a comprehensive review of theoretical and experimental aspects of the precision Higgs program at the International Linear Collider (ILC), has been contributed to the 2013 Snowmass Proceedings. This document has also been posted to the arXiv [PDF]. A link to the most recent version of this paper can be found in Section III of the academic website.

September 21, 2013: Pictures from the Higgs Days 2013 meeting have been posted to the Santander section of my webpage of photographs.

September 18, 2013: My talk entitled 2HDM Theory and a strategy for benchmarks given at Higgs Days 2013 in Santander, Spain has been posted to Section VII of the academic website.

September 15, 2013: My talk entitled Higgs Physics at the ILC given at Scalars 2013 in Warsaw, Poland has been posted to Section VII of the academic website.

August 26, 2013: My paper in collaboration with Patrick Draper, entitled Decoupling of the right-handed neutrino contribution to the Higgs mass in supersymmetric models, was published today in the European Physical Journal C. This paper demonstrates that the contributions from the right-handed neutrino sector to the computation of the mass of the lightest CP-even Higgs boson of the MSSM are negligibly small, as expected from the decoupling theorem (thereby disproving a suggestion in the literature that such contributions could be as large as a few GeV). A link to this paper can be found in Section II of the academic website.

July 25, 2013: My talk entitled Higgs physics--approaching the decoupling limit, given at Higgs Hunting 2013 in Orsay, France, has been posted to Section VII of the acadmeic website.

July 8, 2013: My talk entitled Decoupling and the MSSM Higgs Mass, given at the KITP workshop entitled "LHC--The First Part of the Journey," has been posted to Section VII of the academic website.

July 2, 2013: My talk entitled BSM Higgs Physics at the ILC given at the Snowmass Seattle Energy Frontier Workshop at the University of Washington in Seattle has been posted to Section VII of the academic website.

June 7, 2013: Team Re-Entry wins the Spring UCSC Intramurals Coed Softball Championship in decisive fashion with a 20--5 victory over its opponent. For more details click on this link.

May 20, 2013: My talk entitled The MSSM Higgs Mass Revisited given at the Planck 2013 Conference in Bonn has been posted to Section VII of the academic website.

May 15, 2013: My talk entitled 2HDM Benchmarks for LHC Higgs Studies for the BSM Heavy Higgs meeting at CERN updates a similar talk given last month at UC Davis. A link to this latest version has been posted to Section VII of the academic website.

April 24, 2013: My paper in collaboration with Patrick Draper, entitled Decoupling of the right-handed neutrino contribution to the Higgs mass in supersymmetric models was posted today on the arXiv. A link to this paper can be found in Section II of the academic website.

April 23, 2013: My talk entitled 2HDM Benchmarks for LHC Higgs Studies given at the HEFTI workshop on the LHC Higgs Signal at UC Davis has been posted to Section VII of the academic website.

March 22, 2013: A preliminary note entitled Toward a set of 2HDM benchmarks has been posted to Section VI of the academic website and was contributed to the LHC HXSWG BSM Heavy Higgs Meeting (listed in Section VII of the academic website).

March 12, 2013: My paper in collaboration with P.M. Ferreira, Rui Santos and Joao P. Silva investigating the viability of two near mass-degenerate Higgs bosons with a mass of about 125 GeV is now published in Physical Review D. A link to this paper is given in Section II of the academic website.

March 11, 2013: My talk entitled A Higgs Hunter's Perspective, given at the Aspen Particle Physics Winter Conference, Higgs Quo Vadis, has been posted to Section VII of the academic website.

February 25, 2013: My presentation to Physics 205 can be found in Section V of the academic website.

February 14, 2013: My talk entitled Alternative futures for the Higgs data: are we approaching or receding from the decoupling limit?, given at HPNP2013 in Toyoma, Japan, has been posted to Section VII of the academic website.

January 10, 2013: My talk entitled A Higgs Hunter's Perspective, given at the Higgs Symposium at the Higgs Centre for Theoretical Physics, University of Edinburgh, has been posted to Section VII of the academic website.

January 4--6, 2013: The Search for Fundamental Physics: Higgs Bosons & Supersymmetry, a Symposium in Honor of Michael Dine and Howard Haber on the occasion of their 60th Birthdays.

News items from 2012

December 21, 2012: My talk entitled: Workshop Summary: Revisiting the Higgs Wishlist, given at the KITP Miniprogram: Higgs Identification, has been posted to Section VII of the academic website.

December 7, 2012: My talk entitled Mass-Degenerate-Higgs Hunters Explore the Two-Higgs-Doublet Model, given at the West Coast LHC Theory meeting held at UC Riverside, can be downloaded from Section VII of the academic website.

November 29, 2012: I gave the UCSC colloquium entitled The Higgs Boson Unleashed. [PDF | PPTX]

November 13, 2012: A preprint on two-Higgs-doublet models that can accommodate an enhanced γγ signal and a slightly different invariant mass peak in the ZZ^*→4 leptons and γγ channels was posted to the arXiv. A link to this preprint is located in Section II of the academic website.

October 24, 2012: My talk on the Two-Higgs Doublet Model, presented at the 2012 ATLAS Analysis Jamboree on Higgs Searches, can be downloaded from Section VII of the academic website.

October 7, 2012: In the annual SLAC softball game, Team Research built an early sixteen run lead, and then barely held on to defeat Team Accelerator 18--17. Meanwhile, the UCSC intramural coed softball league kicks off its fall season on October 19. See Section IX of the academic website for further details.

September 18, 2012: My favorite 126 GeV interpretation, presented at Higgs Days at Santander 2012, can be downloaded from Section VII of the academic website.

August 31, 2012: My talk on the necessary conditions for spontaneous CP violation presented at the Multi-Higgs Workshop in Lisbon can be downloaded from Section VII of the academic website.

July 23--24, 2012: My two lectures entitled EWSB Basics, presented at the 40th SLAC Summer Institute, can be downloaded from Section VII of the academic website.

July 4, 2012: Search for Higgs boson reveals new particle (for further details, see the CERN update in the search for the Higgs boson).

The History of Particle Physics at the Aspen Center for Physics, by Howard Haber and Joseph Lykken

June 7, 2012: Presentation of a talk entitled "Homing in on the Higgs Boson" to the SPS Chapter at UC Santa Cruz [PDF]

March 13, 2012: American Physical Society Viewpoint by Howard E. Haber:
Homing in on the Higgs Boson.

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Last Updated: December 3, 2024

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