FALL QUARTER 2011 


Tuesday, December 13: 10:30am 
Location: ISB 102 
Yurii Maravin (Kansas State) 
Title: Studies of diboson production at CMS 
Study of diboson production is an important test of the standard model because of its sensitivity to the selfinteraction between gauge bosons via trilinear gauge couplings. These selfinteractions are a direct consequence of the nonAbelian gauge symmetry of the standard model and are a necessary ingredient to construct renormalizable theories involving massive gauge bosons that satisfy unitarity. In this talk results of studying diboson production at CMS are described, based on the analysis of 2010 and 2011 data sets. 

Thursday, December 8: 11:00am 
Location: NS2 307 
Jessica Goodman (UCI) 
Title: Rsymmetry Matching in SUSY Breaking Models 
Low energy descriptions of metastable supersymmetry breaking models often possess an accidental Rsymmetry. This creates an obstacle when constructing viable extensions of the Standard Model since an unbroken Rsymmetry forbids gaugino masses. It has been shown that the Rsymmetry can be broken in O'Raifeartaighlike models where some chiral superfields carry negative Rcharge. This could allow one to write terms in the superpotential with negative exponents. Unless forbidden by symmetries of a UV completion, these terms would be generated dynamically and destabilize the SUSY breaking minimum. I will discuss UV completions of these Rsymmetry breaking O'Raifeartaigh models and show that the Rsymmetry of the IR description can be mapped to an anomalous or anomalyfree Rsymmetry of the UV theory. 

Tuesday, November 22: 10:30am 
Location: ISB 310 
JeanFrancois Arguin (LBL) 
Title: Improving the sensitivity of the top quark charge asymmetry measurements at the LHC 
Abstract:
Recent measurements of the top quark charge asymmetry performed at both CDF and DZero produced tantalizing deviations from the SM prediction. Given that the dataset for these analyses will not improved dramatically, decisive confirmations will be required by the LHC experiments. After reviewing the measurements performed at the Tevatron, I will discuss the challenges to perform these measurements at the LHC. In particular I will describe how one needs to exploit the large datasets of top quarks at the LHC to compensate for the difficulty to perform such a measurement in a symmetric protonproton collider environment. 

Tuesday, November 15: 12:30pm 
Location: ISB 310 
Vikram Rentala (Arizona/UCI) 
Title: Discriminating models of physics Beyond the Standard Model at the LHC 
Abstract:
Many BSM theories predict new heavy particle states that are identical to their SM counterparts but are heavier. In SUSY, thesuperpartners differ in spin by a halfinteger from their SM counterparts, whereas KaluzaKlein resonances have the same spin as the SM zero modes. Measuring spin thus provides a crucial handle on distinguishing new physics models at the LHC. The first part of this talk is about spin measurement of new particles at the LHC using the azimuthal angular distribution of decay products from a parent particle whose spin we wish to measure. This technique is model independent and relies only on simple angular momentum rules and quantum mechanics. In the second part of the talk I will discuss WZ scattering at the LHC. We find that the same azimuthal angle can be used as a probe of a strongly coupled Higgs sector. 

Tuesday, November 15: 10:30am 
Location: ISB 102 
Alberto Mariotti (VUB University in Brussels) 
Title: PseudoGoldstini in field theory 
Abstract:
First, I will briefly introduce some aspects of supersymmetry breaking and its mediation to the MSSM. I will then consider a scenario with two susy breaking hidden sectors which decouple when their respective couplings to the visible particles are switched off. In such a scenario one expects to find two light fermions: the goldstino and the pseudogoldstino. I will discuss the mass induced to the pseudogoldstino by radiative corrections in a general gauge mediation framework, showing that this mass is naturally around the GeV scale. I will finally discuss some of the phenomenological consequences and possible collider signatures. 

Tuesday, November 8: 10:30 am 
Location: ISB 310 
Jaewon Song (Caltech) 
Title: Renormalization (in)dependence of N=2 SCFT and 4d/2d correspondence 
Abstract:
TBAWe study instanton partition function of 4d N=2 SCFT arising from the 6d (2, 0)theory compactified on a Riemann surface. There are different realizations of the same gauge theory coming from the accidental isomorphisms of the lowrank Lie algebras. We find such different realizations of the same gauge theory give the same instanton partition function only after a nontrivial mapping of the UV gauge couplings. The map can be understood as a cover/base map of the corresponding Riemann surface. Using this relation, we extend the 4d/2d AldayGaiottoTachikawa correspondence to Dtype quivers and also to nonlinear A_1 Sicilian quiver theories. 

Tuesday, November 1: 12:30pm 
Location: ISB 102 
William Quayle (University of Wisconsin) 
Title: Results from Higgs Boson Searches at the LHC 
Abstract:
The last year has seen tremendous progress on the Higgs boson search at LHC. This talk will review the methods we use to search for the Higgs boson at ATLAS, the results from this year's data, and the prospects for Higgs discovery in the next few years. 

Tuesday, October 25: 12:30pm 
Location: ISB 310 
Elina Fuchs (DESY/University of Göttingen) 
Title: A generalized NarrowWidth Approximation for interference effects in the MSSM 
Abstract:
The "NarrowWidth Approximation" is a convenient tool for the factorization of a longer decay chain into production and subsequent decay of a particle with a small width compared to its mass. However, this approximation cannot be applied in the case of sizable interference between propagator contributions of different particles that are close to their mass shell. The spectrum of the MSSM may contain particles with a mass difference of the order of their decay widths. In order to deal with such a situation, a generalization of the usual NarrowWidth Approximation is analyzed which allows for a consistent treatment of interference effects between such nearly massdegenerate particles. The phenomenological consequences will be discussed for the example process of Higgs boson production and subsequent decay from the decay of a heavy neutralino. 

Friday, October 21: 10:30am 
Location: ISB 102 
Daniel Sudarsky (Instituto de Ciencias Nucleares, UNAM) 
Title: The inflationary origin of the seeds of cosmic structure: quantum theory and the need for novel physics.. 
Abstract:
The observations of the first traces of cosmic structure in the Cosmic Microwave Background are in excellent agreement with the predictions of Inflation. However as we shall see, the standard inflationary account, is not fully satisfactory as it can not explain the transition from an homogeneous and isotropic early stage to a latter one lacking those symmetries. The problem can be seen to be related to the exacerbated manner in which the interpretational problems of quantum theory appear in the cosmological setting, and in particular to the inadequacies of the decoherence approach to the task at hand. We will argue, therefore, that an extra ingredient, corresponding to novel physics, is needed to complete the usual account for the emergence of the seeds of structure, and that, as suggested by R. Penrose and L. Diosi, quantum gravity might be the place from where this new physics ultimately emerges. We will show that generically such new ingredient affects in very specific ways the observational predictions and we will argue that very high precision observations, can be used to constrain various aspects of phenomenological proposals made in this regard. 

Thursday, October 20: 12:30pm 
Location: NS2 307 
Katie Richardson (University of New Mexico) 
Title: Dark matter parameters from neutrino telescopes 
Abstract:
In this talk, I will discuss how neutrino telescopes may help us extract dark matter parameters and can in fact place the most stringent bounds on the spindependent dark matternucleon scattering crosssection. In particular the dark matter annihilation final state provides a distinctive signature that allows us to discriminate among classes of dark matter models. Models with gauge boson or tau final states alongside neutrino final states are distinguishable, and the theoretically wellmotivated U(1)_BL extension of the MSSM produces just such a mixture of final states. It is feasible that the energy reconstruction capability of the IceCube neutrino telescope will preserve the important features. Finally, I will address the prospect for differentiating neutrino flavor final states from one another.


Tuesday, October 18: 12:30pm 
Location: ISB 310 
Ze'ev Surujon (UC Irvine) 
Title: WIMPless Dark Matter in AnomalyMediated Supersymmetry Breaking with Hidden QED 
Abstract:
In anomalymediated supersymmetry breaking, superpartners in a hidden sector have masses that are proportional to couplings squared, and so naturally freeze out with the desired dark matter relic density for a large range of masses. We present an extremely simple realization of this possibility, with WIMPless dark matter arising from a hidden sector that is supersymmetric QED with SU(N_F). Dark matter is multicomponent, composed of hidden leptons and sleptons with masses anywhere from 10 GeV to 10 TeV, and hidden photons provide the thermal bath. The dark matter selfinteracts through hidden sector Coulomb scatterings that are potentially observable. In addition, the hidden photon contribution to the number of relativistic degrees of freedom is in the range \Delta N_eff ~ 0  2, and, if the hidden and visible sectors were initially in thermal contact, the model predicts \Delta N_eff ~ 0.2  0.4. Data already taken by Planck may provide evidence of such deviations. 

Tuesday, October 11: 12:30pm 
Location: ISB 310 
David Sanford (UC Irvine) 
Title: The Compensator FTerm in Anomaly Mediation 
Abstract:
I will discuss recent work reconsidering the derivation of anomaly mediated supersymmetry breaking. I will present a general formalism where the Fterm of the conformal compensator superfield is arbitrary. This allows for a continuous interpolation between the original derivation and a more recent DineSeiberg derivation of anomaly mediation. This derivation shows explicitly that the physical soft parameters are independent of the compensator Fterm and results of two formalisms agree. Finally, I will discuss the role of supersymmetric and nonsupersymmetric thresholds in the effective low energy Lagrangian as well as the effects of explicit small mass parameters (such as μterm) on the superpartner spectrum. 

SPECIAL SCIPP SEMINAR: Thursday, October 6: 2:00pm 
Location: ISB 310 
Georges Goetz (Stanford) 
Title: A Spectral Method for Automated Neuron Identification in Large Scale Datasets 
Abstract:
Spike sorting is a well documented problem which involves discrimination between the activity of different neurons and background electrical noise based on analysis of the shape of the waveforms collected on one or more electrodes in neural tissue. Classical spike sorting techniques apply dimensionality reduction algorithms such as PCA to the recorded waveforms, before running clustering algorithms such as KMeans or Expectation Maximization on the resulting data in order to separate spikes coming from different neurons. With these methods, correct identification of the number of neurons found on an electrode is challenging. Performance also strongly degrades when the neuron waveforms change over time, for example in the case of bursting neurons. In this talk, we present a novel spikesorting algorithm based on the clustering method known as "Spectral Clustering". We show how to apply this technique on very large datasets (hundreds of thousands of action potentials) with nontrivial cluster shapes. Our algorithm provides a simple quantitative criterion for determining the number of neurons found on an electrode. Performance of this novel algorithm was compared with that of a well established automated clustering method and of manual clustering of three largescale recordings of rat retinal activity. The novel algorithm was shown to perform as well as manual clustering and significantly outperformed the previous automated method. 

Wednesday, October 5: 2:00pm 
Location: ISB 310 
GianFranco Dalla Betta (University of Trento) 
Title: Recent developments of 3D and active edge silicon sensors 
Abstract:
3D radiation sensors consist of a threedimensional array of vertical columnar electrodes of both doping types, etched perpendicularly to the wafer surface and penetrating through the entire substrate. In planar detectors the depletion voltage and the collected charge depend on the substrate thickness; on the contrary, in 3D sensors these features depend on the detector layout, i.e., on the distance between the columnar electrodes, which can be short enough to yield full depletion and high electric fields at low bias voltage, thus allowing for short collection times and high radiation hardness. One important evolution of the 3D concept, the socalled "active edge" should also be mentioned. This technique makes use of deep ohmic trenches to terminate the detectors, thus eliminating the need of the cutting procedure and reducing the insensitive edge region to less than 10 μm, to be compared to few hundreds μm for standard planar detectors. This option enables building large area seamlessly tiled detector matrices, i.e., without sensor overlap within the same layer, and thus greatly facilitates the layout, reduces the material budget, and improves the momentum resolution. Besides full3D detectors with active edges pioneered by S. Parker and collaborators in the late 90's and fabricated at the Stanford Nanofabrication Facility, other modified 3D detectors have been proposed in the past few years, among them 3DSTC (Single Type Column) and 3DDDTC (Doubleside Double Type Column) detectors, aiming at a simplification of the manufacturing technology in view of volume productions. In particular, the 3DDDTC approach (in two slightly different versions) is being pursued CNMIMB (Barcelona, Spain) and by FBK (Trento, Italy). 3D sensors are currently emerging as one of the most promising technologies for innermost layers of tracking at the foreseen upgrades of the Large Hadron Collider. In particular, in the past few years, important progress has been made in 3D sensors due to the anticipated installation schedule of the ATLAS Insertable B Layer during the first long shut down of the LHC in 20132014. Within the ATLAS 3D Sensor Collaboration, the doublesided 3D technologies from FBK and CNM have been chosen for the IBL Sensor Qualification, with very good results both in terms of tracking performance, radiation hardness and fabrication yield. This talk will review the recent developments of 3D and active edge sensors in Trento, including design and technological aspects as well as selected results from the electrical and functional characterization. 

Monday, September 26: 10:30am 
Location: ISB 310 
Alexander Dolgov (INFN) 
Title: Electric and magnetic screening in plasma with charged Bose condensate 
Abstract:
The screening of external electric and magnetic fields in plasma with electrically charged Bose condensate is considered. The plasma is supposed to be electrically neutral, the charge of the condensate being compensated by other particles. It is shown that the screening behavior of electrically charged impurities is drastically different from the usual Debye law. In particular, the screening becomes power law and oscillating with distance. The latter is similar to Friedel oscillations in plasma with strongly degenerate fermions but physics is different. Similar behavior is found for penetration of magnetic field into plasma, which very much differs from the usual Meissner exponential damping. The results may have applications for high temperature superconductors in BEC phase and for generation of large scale magnetic fields in the early universe. The latter could be seeds of the observed galactic and intergalactic magnetic fields. 

