Tuesday, December 13th, 10:30 AM
ISB 102

Initial results from the Pierre Auger Experiment

Troy Porter (LSU)

The Pierre Auger Observatory is a major international effort aimed at a high-statistics study of the highest energy cosmic rays. It is the first experiment designed to work in a hybrid mode, incorporating a surface array of 1600 water Cherenkov particle detectors spread over 3000 square kilometres with overlooking fluorescence telescopes placed on the array boundary. Data taking with a large part of the detecting apparatus started in mid-2003, with first physics results reported this past northern summer. I will give a general description of the experimental set-up and present some of the initial results.


Tuesday, December 6th, 10:30 AM
ISB 310

Out-of-this-World Physics: From Particles to Black Holes

Greg Landsberg (Brown University)

Search for large and small spatial extra dimensions is one of the most exciting new directions in our quest for physics beyond the Standard Model. LEP collider and "tabletop" gravitational experiments have already set constraints on the strength of gravity at short range. The most interesting opportunities in probing extra dimensions in the near future will become available with the current and next generation of hadron colliders: the upgraded Tevatron and especially LHC, where the ultimate tests of the new models of gravity will be accomplished. I'll discuss various effects of extra dimensions that can be seen sought experimentally, including the most striking possibility of black hole production at the LHC.


Tuesday, November 15, 10:30 AM
ISB 102
Note: unusual location

Dark Matter Searches with GLAST

Larry Wai (SLAC)

The GLAST Large Area Telescope (LAT) is in its final stage of integration and test at the Stanford Linear Accelerator Center. I will give an update on how it's going and show pictures. I will discuss how to use GLAST to search for WIMP dark matter annihilation gamma rays, starting with overall strategy, and focusing on a few example analyses. I will also discuss how GLAST will complement other dark matter searches. As time permits, I will touch on other GLAST "hot topics", like searches for variability in sources and the relevance to underlying astrophysics."


Monday, November 14, 10:30 AM
ISB 102
Note: unusual time and location

Particle Acceleration at Astrophysical Shocks

Pasquale Blasi (INAF, Osservatorio Astrofisico di Arcetri )

Some modern issues in the investigation of cosmic ray acceleration at astrophysical collisionless shock waves will be discussed, with special emphasis on the non linear processes that enter the description of particle reaction on the shock itself and magnetic field self-generation at the shock fronts. The relevance of these topics for the interpretation of some cosmic ray observations will be assessed.


Tuesday, November 1, 10:30 AM
ISB 235
Note: Unusual location

Gamma Rays from Lightning

David Smith (SCIPP)

Millisecond flashes of gamma rays were first discovered above thunderstorms a decade ago with the Compton Gamma-Ray Observatory. New data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) show these events to be more common than previously thought, with photon energies as high as 20 MeV. Modeling and joint radio observations are now teaching us how these flashes relate to lightning physics via relativistic runaway breakdown of air. I will review the physics of this process, place TGFs in the context of other phenomena of atmospheric electricity, and show the latest results and conclusions.


Tuesday, October 25th, 10:30 AM
ISB 310

Results from SLAC E-158: Running of the Weak Coupling Constant and a Study of Parity Violation in Moller Scattering

Mike Woods (SLAC)

The E158 experiment at SLAC has made the first measurement of parity violation in electron-electron (Moller) scattering. The experiment measures the right-left parity-violating cross-section asymmetry (APV) in the elastic scattering of 45 and 48 GeV longitudinally polarized electron beams with unpolarized electrons in a liquid hydrogen target. We find APV = [-131 +- 14 (stat) +- 10 (syst)] parts per billion, with a significance of 8.3sigma for observing parity violation. In the context of the Standard Model, this yields a measurement of the weak mixing angle, sin 2 (thetaW-eff)(Q 2 = 0.026 GeV 2 ) = 0.2397 +- 0.0010 (stat.) +- 0.0008 (syst.). This value of the weak mixing angle is 4% higher than what is observed at Q 2 =M_Z 2 (from measurements of Z-pole asymmetries at LEP and SLC). This establishes running of the weak mixing angle, due to electroweak radiative corrections, with 6.2sigma significance. The result is consistent with Standard Model expectations and sets limits on new physics contributions at the TeV scale. We also present results for the first observation of a single-spin transverse asymmetry in Moller scattering, and results for longitudinal and transverse asymmetries in electron-proton scattering.


Tuesday, October 18, 10:30 AM
ISB 102

Gamma-Ray Bursts: from Swift to GLAST

Bing Zhang's (UNLV)

The study of gamma-ray bursts (GRBs) enters a new era following the launch of Swift in last November. I will review how the latest Swift data greatly advance our understanding of GRBs, including fireball composition, GRB emission site, GRB immediate environment, central engine activity, etc. Based on the previous theoretical studies and the lessons learned from the Swift observations, I will foresee some possible breakthroughs in the GLAST era, including a possible long-term GeV afterglow and a direct diagnosis of the wind environment.


Tuesday, October 11, 10:30 AM
ISB 310

Radiation Tolerant Tracking Detectors for the sLHC

Mara Bruzzi (Florence University and SCIPP)

The future upgrade of luminosity of the Large Hadron Collider up to 10^{35} cm^{-2} s^{-1} will pose severe requirements to silicon tracker detectors due to increased fast hadron fluences up to 10^{15}-10^{16} cm^{-2}. An intense research activity is presently carried on by the HEP community in view to increase the radiation hardness of silicon detectors to this fluence range by proper material and device engineering solutions. The most promising results, recently achieved with planar devices made with p-type Float Zone as well as with n- and p-type Czochralski silicon will be reviewed, especially focussing on the research activity performed in the framework of the RD50 CERN Collaboration and the SMART INFN project.


Tuesday, October 4, 10:30 AM
ISB 310

New Results from the Proton Computed Tomography Project

Jason Feldt (SCIPP)

The pCT project is a collaboration between doctors and particle physicists. At Loma Linda University Medical Center, cancer patients are receiving radiation treatment with proton beams, which is a more precise form of cancer therapy due to the well defined range of protons in matter. But treatment planning still makes use of x-ray Computed Tomography, leading to image uncertainties of several mm.
We are working on imaging the patient with the proton beam itself, and have now finished a beam test where we confirmed the predictions of the most likely path (MLP) by SCIPP's own David C. Williams.


Tuesday 27 September, 10:30 AM
ISB 102

The MAGIC Telescope: Project Status and Source Observations

David Paneque (Max-Planck-Institut fur Physik)

The MAGIC Telescope is an Imaging Air Cherenkov Telescope (IACT) located on the Canary island of La Palma (28.8 deg N, 17.9 deg W), at the Roque de los Muchachos Observatory (2200 m above sea level). The challenging goal of the experiment is to observe with high sensitivity the energy region between 30 GeV and 300 GeV in gamma-ray astronomy, which is unexplored now, by lowering the threshold energy Eth as compared to previous generation of IACTs. Observations in this new window of the electromagnetic spectrum are expected to provide key data for the understanding of a wide variety of astrophysical phenomena belonging to the so-called "non-thermal Universe", like the acceleration processes in Active Galactic Nuclei, the radiation mechanisms of pulsars and Supernova Remnants, and the enigmatic Gamma Ray Bursts. In the talk, the working principle of IACTs as instruments for performing gamma-ray astronomy will be shortly reviewed, and the MAGIC telescope will be described, stressing some of the main technologic developments carried out in order to achieve the required performance. The current status of the project will be givien; and the observations of several gamma-ray sources will be reported.

Summer Seminar

Wednesday, August 24th , 11:00 am
ISB 310
Note: unusual time

A Proposal For What We Might See At The LHC

Tom Banks (SCIPP)

I will present a new model of TeV scale physics based on exotic ideas about the relation between supersymmetry breaking and the cosmological constant.  The model solves many of the problems of conventional SUSY models and predicts a host of new phenomena, including a new strongly interacting sector at the TeV scale, tan \beta  \sim 1, and a new kind of dark matter candidate.   It has a residual "strong CP like" problem and appears to predict too large a neutron electric dipole moment (just as the standard model does for generic values of parameters).

June 2005

Friday, June 24th, 11:00 am
ISB 310
Note: unusual time

Upward Going muons in Super-Kamiokande

Shantanu Desai (Penn State)

Super-Kamiokande (Super-K) is a water Cherenkov detector located underground in the Japanese Alps. It is able to detect neutrinos spanning over 6 decades in energy. In this talk I will present various physics and astronomy results from upward going muons with the first 5 years of Super-K data. "Upward going muons" are muons which enter the detector from below and are produced by neutrino interactions in the rock below the detector. These constitute the highest energy neutrinos seen in Super-K. Results from neutrino oscillation analysis as well as a variety of astrophysical searches (WIMPs, GRBs, SGRs etc.) using upward going muons will be discussed.


Tuesday, June 7th, 10:30 am
ISB 310

Solar Neutrino Flux Variability: the Evidence and its Implications for Solar Physics and Neutrino Physics

Peter Sturrock (Stanford University)

Early claims of variability of the solar neutrino flux were based on analysis of Homestake data. These claims were never convincing. Since that time, improved datasets have been released by the GALLEX, GNO, SAGE and Super-Kamiokande consortia. These datasets yield strong evidence for harmonic modulation with frequencies characteristic of solar rotation and of certain solar oscillations, with significant implications for solar physics and neutrino physics.


Tuesday, June 7th, 2:00 pm
ISB 310

The Landscape Standard Model 

Scott Thomas (Stanford University)

The Standard Model is conjectured to be the most common realization of the landscape on the branch with supersymmetry broken at a high scale.  Two scenarios for the scale of supersymmtry breaking are considered, each of which leads to a rather tight probablisitic correlation between the top quark and Higgs boson masses. In the first scenario the scale of supersymmetry breaking is taken to be somewhat below the messenger scale.  In this case, supersymmetric boundary conditions for the Higgs self coupling at the supersymmetry breaking scale lead to a most probable value of the Higgs mass of roughly 154 GeV for the current central value of the top mass.  In the second scenario the scale of supersymmetry breaking is taken to coincide with the messenger scale.  In this case, general supersymmetry breaking boundary conditions for the Higgs self coupling lead to a most probable mass of roughly 180 GeV for the current central value of the top mass.  The conjecture presented here implies that the Large Hadron Collider will discover a single Standard Model Higgs boson with mass most likely near one of the values given above, and nothing else.  The numerical values and uncertainties of the most probable Higgs masses can be systematically improved through inclusion of higher order effects within the Standard Model alone.

May 2005

Tuesday, May 31st, 11:00 am
ISB 310
Note: unusual time

Animation of the ATLAS Experiment

Michael Barnett and Joao Pequenao (LBNL)

Work is well underway to animate three aspects of the ATLAS Experiment: construction/overview, passage of particles through the detector, and the interpretation of physics events in ATLAS. Discovery with ATLAS Episode
1: A New Hope Episode
2: The Particles Strike Back Episode
3: The Return of the Jets


Tuesday, May 24th, 10:30 am
ISB 310

Dynamic Force Spectroscopy of Multivalent Mucin1-Antibody Bonds for Drug Targeting

Todd Sulchek (Lawrence Livermore National Laboratory)

Specific targeting of cancer cells with antibodies linked to radionucleotide therapeutics, a technique called radioimmunotherapy, is a promising technique to treat late stages of cancer. Multiple antibodies linked to therapeutics are used to improve binding times to cancer cells, but little quantitative data exists to determine the benefit from multivalency. We used the atomic force microscope (AFM) to measure the single molecule force of binding between Mucin1 (MUC1) protein--a cancer indicator--and an antibody that targets MUC1. By tethering the interacting molecules to a polymer spacer, we separate the specific binding interaction in both space and force. This specific interaction can be blocked through a competition assay. In addition, by measuring the rupture force as a function of force loading rate, we use the methods of dynamic force spectroscopy (DFS) to distinguish between and estimate the thermodynamic bond times for mono-, bi-, and tri-valent binding. The effective bond time rises dramatically with the number of bonds. Moreover, our results support the predictions of a Markovian model for the strength of multiple uncorrelated bonds in parallel configuration.


Tuesday, May 24th, 12:30 pm
ISB 102

Constraints on Dark Matter from Background Radiation

Paul Wesson (Stanford/U. of Waterloo)

Dark matter is not completely black, so we can constrain possible candidates by comparing their decay photons with the intensity of the background radiation of the universe at various wavelengths. This involves a combination of particle physics and cosmological models based on general relativity. Extensions of the latter also provides possible candidates for dark matter, in addition to the usual ones. Our work favours Weakly Interacting Massive Particles, or the higher- dimensional analogs of black holes.


Tuesday, May 17th, 10:30 am
ISB 102
Note: unusual location

Analysis of Astrophysics and Particle Physics Data using Optimal Segmentation

Jeff Scargle (Space Science Division, NASA Ames Research Center)

Detection and characterization of time-domain structures in time series data can be achieved by optimizing a simple, piecewise constant, model. Bayesian changepoint methods provide a convenient model fitness function, and a maximum likelihood approach has even better properties. A new algorithm, following dynamical programming ideas originated by Richard Bellman 50 years ago, yields an exact global optimum over an exponentially large search space in time O(N²). Extension to image and higher dimensional data is immediate. Example applications include detection of transient sources in gamma-ray time series (BATSE, Milagro, GLAST, etc.), identification of intron-exon boundaries in gene sequences, detection of point and extended gamma-ray sources, detection of bioterrorism events in water distribution systems, and characterization of the large scale structure of the Universe.


Tuesday, May 10th, 11:00 am
ISB 310
Note: unusual time

Thoughts About Tracking for the Linear Collider Detector

Bruce Schumm (SCIPP)

I've been doing some very general thinking about approaches to tracking for a Linear Collider Detector. I'll present some of the arguments I've been playing with, and then make the point that microstrip tracking is almost certain to play a role in any detector design for the LC. I'll finish with an overview of the independent efforts on Si microstrip tracking for the LC detector.


Friday, May 6th, 10:00 am
ISB 102
Note: unusual time and location

First Results from the Swift GRB Mission

Neil Gehrels (NASA/GSFC)

Swift is now in orbit after a beautiful launch on November 20, 2004. It is a multiwavelength observatory for transient astronomy.  The goals are to determine the origin of GRBs and their afterglows and use bursts to probe the early Universe.  A new-technology wide-field gamma-ray camera detects more than a hundred GRBs per year to 3 times fainter than BATSE.  Sensitive narrow-field X-ray and UV/optical telescopes are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft.  For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed.  First results from the mission will be presented, including observations of bright GRBs, faint GRBs, short GRBs and a super-giant flare from the soft gamma repeater SGR1806-20.


Monday, May 2nd, 11:30 am
ISB 310
Note: unusual time

X-ray and Gamma-Ray Observations of Active Galaxies as Probes of Their Structure

Greg Madejski (SLAC)

This presentation will cover the current status and progress of research on active galactic nuclei that resulted from observations in the X-ray and gamma-ray bands. The emphasis will be on the nature of the central source, clues regarding the connection to jets in active galaxies, and the radiation processes and content of those jets. I also will give the prospects for the future observations with the upcoming satellite-based X-ray and gamma-ray sensitive instruments such as Astro-E2, GLAST, and NuSTAR.

April 2005

Tuesday, April 26th, 10:30 am
ISB 310

The Radio Afterglow produced by the Giant Flare from the Magnetar SGR 1806-20

Greg Taylor (National Radio Astronomy Observatory)

Magnetars are a small class of slowly spinning neutron stars with extreme surface magnetic fields, ~10^15 Gauss. On 2004 December 27, a giant flare was detected from the magnetar SGR 1806-20, the third such event ever recorded. This burst of energy was detected by a variety of instruments and even caused an ionospheric disturbance in the Earth's upper atmosphere recorded around the globe. I will concentrate on the detection of an initially bright but rapidly fading radio afterglow produced by this outburst, with a luminosity 500 times larger than the only other detection of a similar source. From day 6 to day 80 (and continuing to the present day) we have been following the development of the radio afterglow. A resolved, linearly polarized, radio nebula is seen, expanding at approximately a quarter the speed of light. To create this nebula, at least 4x10^43 ergs of energy must have been emitted by the giant flare in the form of magnetic fields and relativistic particles. The combination of spatially resolved structure, good astrometry, and rapid time evolution allows a study in unprecedented detail of a nearby analog to gamma-ray bursts, and has important implications for the nature of GRBs.


Tuesday, April 19th, 11:00 am
ISB 310
Note: unusual time

New Results on Radiative and Dilepton Decays of B Mesons at BaBar

Al Eisner (SCIPP)

In the standard model (SM), decays of B mesons via the emission of a photon or a dilepton pair are rare occurrences, for which the leading contributions are "electroweak penguin" or (in the dilepton case) box diagrams, involving loops containing high-mass quarks or W bosons. As such, they are promising places to look for physics beyond the standard model, both in branching fractions and in the amount of CP asymmetry. In addition, measurements of the inclusive photon spectrum in radiative decays can be used to extract heavy quark effective parameters which also appear in semileptonic B decays, and are thus relevant to the extraction of the CKM matrix element Vub from such decays. This seminar presents preliminary results from BaBar on inclusive radiative decays to a strange state plus a photon, using two independent methods. New results for exclusive channels include a measurement of time-dependent CP asymmetry (via interference with B-Bbar mixing) in decays to the CP eigenstate KS plus pi0 plus photon. A search for the even rarer decay to D* plus a photon is also outlined. And the full BaBar data sample is used to update results for B decays to K or K* plus a dilepton pair, in which both the branching fractions and the ratio of muon to electron pairs could be influenced by non-SM physics.


Monday, April 11th, 10:00 am
ISB 102
NOTE: unusual time and location

Ensemble Coding of Visual Motion in Primate Retina and Implications for Motion Sensing in the Brain

E. J. Chichilnisky (Systems Neurobiology Lab, Salk Institute)

An essential function of sensory systems is to extract specific information about the environment efficiently from the activity of peripheral neurons. Current understanding of this process is based mostly on examination of how faithfully the activity of an individual neuron represents a sensory variable, such as the number of incident photons or the direction of movement. However, behaviorally important information is usually represented not by the activity of an individual neuron, but by the concerted activity of many neurons. We examined how precisely the ensemble activity of ~100 primate retinal ganglion cells (RGCs) signals the speed of a moving object, a prerequisite for visually guided behaviors such as tracking eye movements and target interception. By extracting motion information from the recorded ensemble retinal activity, we establish how faithfully the retina conveys motion information to the brain, and what aspects of the neural code limit this fidelity. Comparison to human speed discrimination in matched conditions indicates major limits on motion sensing in downstream structures. These findings reveal how population activity conveys visual information and how it influences behaviorally important visual function.

March 2005
Tuesday, March 29th, 10:00 am (ISB 310)
(NOTE: earlier time than newly assigned spring schedule)

Peter Zerwas (DESY Hamburg)

Supersymmetry in Coherent ILC/LHC Analyses

Supersymmetry can provide solutions to central problems in the physics
domain beyond the Standard Model. The LHC and the TeV e+e- linear collider ILC, now at the design level, will be essential experimental instruments in this context: Coherent ILC/LHC analyses can draw a comprehensive and precise picture of the supersymmetric particle sector, which may serve as the proper platform for extrapolations to the fundamental physics areas near the grand unification and Planck scale. The potential of such analyses will be exemplified for minimal supergravity, left-right symmetric extensions involving intermediate scales, and string effective theories.
March 2005

Time: Wednesday, March 16th, 10:00 am

Siannah Penaranda ( Institut für Theoretische Physik, Universität Karlsruhe )

We present results on the analysis of the ratios of branching ratios R=BR(H -> b b-bar)/BR(H -> tau^+ tau^-) and R=BR(H^+ -> tau nu)/BR(H^+ -> t b-bar)
of neutral and charged Higgs boson decays as discriminant quantities between supersymmetric and non-supersymmetric models.
A detailed analysis in the effective Lagrangian approach for the neutral Higgs boson decay rates shows that, with a measurement of +-21% accuracy, the Large Hadron Collider (LHC) can discriminate between models if the CP-odd Higgs boson mass is below 900 GeV. An e+e- Linear Collider at 500 GeV center of mass energy can discriminate supersymmetric models up to a CP-odd Higgs mass of ~1.8 TeV.
For the ratio of charged Higgs boson decays, simulation of measurements of this quantity through the analysis of the charged Higgs production process gb-> t b H^+ and relative backgrounds in the two above decay channels has been performed in the context of ATLAS. A ~12-14% accuracy on R can be achieved for tan beta=50, mH+=300-500 GeV and after an integrated luminosity of 300 fb^-1. With this precision measurement, the LHC can
easily discriminate between models for the two above scenarios, so long as
tan beta > 20.


Thursday, March 3, 11am ISB 310

Progress Report on 3D Sensors

Chris Kenney (Stanford Nanofabrication Facility)

Applications of 3D-architecture, radiation sensors in particle physics and synchrotron instrumentation will be discussed. Variations on the basic 3D concept such as active-edges and partial 2.5D designs as well as tests with photon and charged particle will be presented.

February 2005

Friday, February 18th, 10:00 am (ISB 102)
NOTE: Unusual time and location

Spectral-Total Energy Correlations in BATSE GRBs with Known Redshift

Guido Barbiellini (INFN)

The analysis of the fluence from the large BATSE GRB population confirms
with a few assumptions an interesting spectral-total energy correlation.
This correlation is derived from those (relatively few BATSE) GRBs for
which the red shift has been measured. The environment close to the GRB
could explain this correlation.


Thursday, February 17th, 11:00 am

Gamma-ray emission from SNRs and regions of star formation

Diego Torres (Lawrence Livermore National Laboratory)

In this seminar we present an overview on the observational status of the connection between SNRs and gamma-ray sources. Establishing this connection is essential to prove hadronic cosmic ray acceleration in SNR shocks. We shall mention results from EGRET up to the recent discoveries by HESS, together with prospects for the LAT instrument. The second part of the seminar discusses luminous and ultraluminous infrared galaxies (the strongest star formation sites known in the universe) as gamma-ray emitters, introducing detailed multiwavelength models.


Thursday, February 10th, 11:00 am

Paddy Fox (SCIPP)

Supersoft Supersymmetry breaking and new collider signatures

There are many scenarios known which predict supersymmetry will be seen at the LHC. I discuss a new supersymmetry breaking mechanism and describe some interesting collider signatures.


Thursday, February 3rd, 11:00 am

ISB 102 *note unusual location!

Laurent Gizon (Stanford)

Local Helioseismology

Observations of global solar oscillations have revealed temporal variations in the structure and dynamics of the Sun. It is known that changes in pulsation frequencies correlate with the Sun's magnetic cycle and correspond to perturbations located in the upper solar convection zone. To complement techniques of global-mode helioseismology, which have no resolution in longitude and cannot distinguish the northern from the southern hemisphere, new techniques of local helioseismology are being developed. The goal of local helioseismology is to make 3D images inside the Sun in order to study magnetic structures (e.g. sunspots and active regions), vector flows, and their interactions in the solar interior. I will present recent results based on data from the MDI telescope aboard the ESA/NASA SoHO satellite.

January 2005

Thursday, January 27th, 11:00 am

Andrea Pocar (Stanford University)

Borexino: status and perspectives

Borexino is a liquid scintillator neutrino experiment at the Gran Sasso underground laboratory (LNGS) in central Italy. I will present its potential for detecting solar neutrinos and the physics implications of its possible findings within the frame of neutrino oscillations and towards our understanding of how the Sun burns. Its potential for detecting supernovae and terrestrial neutrinos will also be addressed.
The talk will cover various aspects of the construction of the detector, with particular emphasis on the cleanliness and low radioactivity techniques adopted for the most sensitive parts of the detector, which required unprecedented levels of radioactive contamination. Some results from the CTF prototype will be discussed.
Finally, I will give my perspective on the current situation at LNGS linking it to the constraint it poses for the start of the experiment.


Thursday, January 13th, 11:00 am

Tune Kamae (SLAC)

Up-to-date proton-ISM interaction modeling and "anomalies" related to the cosmic gamma, positron and pbar spectra

We have calculated gamma-ray, positron, anti-proton and neutrino spectra from high energy pp interactions in the astrophysical environment. The calculation includes the diffraction dissociation and incorporates the Feynman scaling violation for the first time. We found that the diffractive process makes light-mass secondary particle spectra harder than the incident proton spectrum, and, that the scaling violation produces more pions and anti-protons than previous calculations based on the scaling model. Combination of the two can explain about a half of the "GeV Excess'' in the EGRET Galactic diffuse gamma-ray spectrum with the local cosmic proton spectrum (power-law index 2.7). The excess can be fully explained if the proton spectral index in the Galactic ridge is harder by 0.2 in power-law index. We also found that the diffractive process enhances positrons over electrons and the scaling violation gives 50-100% higher antiproton yield than without the violation, both in the multi-GeV range. For a power-law proton spectrum of index 2, our interaction model predicts the gamma, e-, e+ and neutrino fluxes be twice higher than the predictions on the Feynman scaling model in the 100TeV range.

November 2004
Monday, November 29th, 11am
ISB 310
Valerie Halyo (SLAC)
Status of Pentaquark Searches (at BABAR and elsewhere)
Monday, November 22, 11am
ISB 310
Nu Xu (Lawrence Berkeley National Laboratory)
Collective Expansion in Relativistic Heavy Ion Collisions -
Search for a partonic equation of state at RHIC

The Relativistic Heavy Ion Collider (RHIC) started to operate in 2000. A large amount of high quality data has been collected by the RHIC experiments. Collective motion with parton degrees of freedom is called partonic collectivity. It is an important part of the equation of state (EOS) of the matter produced in high-energy nuclear collisions. In this talk, I will review the status of RHIC physics and discuss where we stand with respect to a QGP discovery. The focus will be given to collective observables such as transverse radial flow and elliptic flow. We will demonstrate that collectivity has already been developed prior to the hadronic stage in heavy ion collisions at RHIC.
Monday, November 15, 11am
ISB 310
Patrick Decowski (UC Berkeley)
Measuring Neutrino Oscillation with Reactors

The KamLAND reactor anti-neutrino experiment uses one kton of liquid scintillator to detect electron anti-neutrinos with the inverse beta-decay reaction. The electron anti-neutrinos are produced during the fission process in 53 Japanese commercial power reactors, at an average distance of 180km from KamLAND, and can oscillate to a different flavor on their way towards the experiment. KamLAND measures the electron anti-neutrino spectrum and compares it to the spectrum calculated from reactor operational records. Neutrino oscillation will cause a spectral distortion relative to the expected spectrum in the absence of neutrino oscillation. I will discuss reactor experiments and present the results of a recently completed analysis of 766.3 ton-year of KamLAND data, showing evidence for spectral distortions and further solidifying the case for neutrino oscillation.
Monday, November 8, 11am
ISB 310
Wolfgang Menges (Queen Mary, University of London)
Four years after LEP: What have we learned about W-bosons?

The LEP collider at CERN was operated very successfully above the Z resonance. Each of the four experiments collected around 10000 W-pair events over 5 years at centre-of-mass energies between 160 and 208 GeV. I will review the analysis strategies to measure the properties of the W-boson like cross-section, mass and couplings to gauge bosons. The theoretical and experimental challenges of these measurements are discussed in some detail and the status of the final results is given.
October 2004
Monday, October 25, 2004 11:00 am
ISB 310
Michael Strauss (University of Oklahoma)

Measurements of the Masses, Mixing and Lifetimes of B Hadrons at the Tevatron

B Hadrons are copiously created at the Tevatron. Measurements of the properties of these hadrons can help confirm the Standard Model, reveal new physics, and explore the source of CP violation. The D0 and CDF collaborations have made a number of new measurements of the properties of these B hadrons over the last few months. This talk will present an overview of the recent measurements of B hadron properties at the Tevatron.
Tuesday, October 19, 2004 11:00 am (note unusual time!)
ISB 310
Henri Bachacou (LBNL)

Measurement of the t\bar t Production Cross Section Using Lepton + Jets Events with Secondary Vertex b-Tagging at CDF

Monday, October 18, 11:00 am
ISB 310
Kirk Gilmore (Lick Observatory)

Optical Detectors for Astronomy

Friday, October 1st 11:00am (note unusual time!)
ISB 310
Martin Tluczykont (Ecole Polytechnique)

HESS: Very High Energy Astrophysics with the new Generation of
Cherenkov Telescopes

The High Energy Stereoscopic System (HESS), located in Namibia , is operating four 12m Cherenkov telescopes in the GeV/TeV energy regime (E>100GeV). Since first light in June 2002, data was taken throughout the buildup phase of the experiment, which was completed in December 2003. Outstanding results have been achieved in the first two years of operation, demonstrating that the imaging air Cherenkov technique has reached maturity, showing the high potential for more exciting results in the future.
The status and results of the experiment will be reviewed and I will present the first ever GeV/TeV astronomical image, the detection of a new class of TeV-emitters and the impact of the signal from the Galactic Center on the question of dark matter. Furthermore, plans for the second phase of the
experiment, consisting of an additional huge telescope, will be addressed.

Monday, October 4, 11:00am
ISB 310

Dr. Raghunathan Srivatsan (Norfolk State University)

Measurement of Cosmic Ray Helium flux at small atmospheric depths using the BESS spectrometer

The BESS (Balloon-borne Experiment with Superconducting Spectrometer) detector is a high resolution spectrometer with a large acceptance to perform sensitive searches of cosmic ray antiparticles, as well as the precise measurement of absolute fluxes of various cosmic ray particles at the top of the atmosphere. The energy spectrum of antiprotons and many other cosmic ray particles have been very accurately determined during eight successive BESS flights. We analyzed the data collected during 1999 flight when the balloon ascended continuously from ground level to the top of the atmosphere to determine the flux of cosmic ray helium at various atmospheric depths. In this talk, the BESS experiment and the data analysis will be described, and our results on the helium flux measurements at small atmospheric depths will be discussed.

September 2004

Wednesday, September 29th 11:00am (note unusual time!)
ISB 310

Wim de Boer ( University of Karlsruhe )

Indirect Evidence for WIMP Dark Matter Annihilation

Monday, September 20th
2:00pm - NOTE - unusual time!

Daniel Ferenc (UC Davis)

Status of the MAGIC Gamma-Ray Telescope and Novel Photosensor

June 2004

Monday, June 7, 4:00pm

Gabriele Simi (SLAC)

The BaBar Silicon Vertex Tracker : Radiation Damage and Other Operational Issues

Tuesday, June 1 (note different day!)

Abraham Seiden (SCIPP)

"Status of the LHC Program"

May 2004

Monday, May 17, 4:00pm

Maxwell Chertok (UCD)

"CDF Run II and the Search for New Phenomena"

The Fermilab Tevatron is the world's highest energy particle collider, presently smashing antiprotons and protons at a center of mass energy of 2 TeV. The status of the Fermilab Tevatron Run II is given, including prospects for ultimate integrated luminosity. The CDF II detector, along with upgrades for the high luminosity part of the run are presented. The terminated silicon detector upgrade is also described. Recent results from CDF New Phenomena analyses are presented including those covering Supersymmetry, Higgs and Leptoquark searches.

Monday, May 10, 4:00pm

Richard Scalzo (LBNL)

"Observations of the Gamma-Ray Blazar W Comae with STACEE "  

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is ground-based telescope sensitive to high-energy gamma rays (> 100 GeV). It uses as its primary optic an array of solar heliostat mirrors, with total collection area of 2300 m 2 , to concentrate Cherenkov light from air showers initiated by gamma rays onto an array of photomultiplier tubes. The STACEE experiment was used to observe the AGN W Comae (ON+231) in the spring of 2003. Observations at other wavelengths strongly constrain theoretical models of gamma-ray emission from the relativistic jet in W Comae. These models predict significantly different fluxes of gamma rays above 100 GeV, depending on the types of particles responsible for the high-energy emission (electrons or protons). The results of the STACEE observations will be discussed within this context.

Monday, May 3rd, 4:00pm

Hiro Tajima (SLAC)

"Development of Next Generation Gamma-ray Space Telescopes"

We are developing a next generation of Compton telescopes to explore the gamma-ray universe in an energy band 0.1-20 MeV, which is not well covered by the present or near-future missions. The key feature of such telescopes is the high energy resolution to achieve precise angular resolution and large background rejection capability. It can also measure the polarization of the gamma-ray, which provides rich information to study particle acceleration mechanisms in astronomical objects. I will describe science objectives, instrument designs and test results from prototype detectors. In particular, energy resolution, angular resolution and polarization capabilities have been measured.

April 2004
Monday, April 26, 4:00pm

David A. Williams (SCIPP)

"A Wide-Aperture View of the TeV Gamma-Ray Sky:
Results from Milagro"

Milagro is a water-Cherenkov detector in the Jemez Mountains of New Mexico, designed to study air showers around 1 TeV. Compared to atmospheric Cherenkov telescopes which operate in the same energy range, Milagro has a wide field of view (~2 sr) and operates around the clock. These features are particularly suitable for surveying the sky for previously unknown or unanticipated sources, as well as for observing prompt emission from gamma-ray bursts. Results from a Milagro survey of the northern sky will be presented, as well as a preliminary detection of emission from the galactic plane and searches for WIMP annihilations in the vicinity of the sun and very high-energy emission from gamma-ray bursts.

Monday, April 19, 10.30am - Note Special Time

Anthony Aguirre (SCIPP)

"Eternal Inflation, Multiple Universes, and other Dark Matters"

Several ideas in cosmology, including inflation, string cosmology, and quantum cosmology, have led to the notion of multiple "universes" with different properties. This immediately raises the question of which (theoretical) universe we should compare to ours, and also provides a context for the "anthropic principle". I will outline some of the issues and problems that arise in multiverse theories, and describe some specific progress that has been made toward resolving (or making more acute) these problems.

Monday, April 5, 4:00 - Note Special Time

Joel Primack, Michael Riordan, Bruce Schumm (SCIPP)

"Writing about Physics for the General Public"

It has recently been recognized that presenting basic science research at a level appropriate for the general public is an essential element of a healthy and well-supported science program. We will discuss our experiences - the rewards as well as the hurdles we faced - in writing and promoting books that we have written to communicate science at a level appropriate for a reader with an interest but no formal background in the material we are presenting. We will compare our experiences, looking for common threads as well as for ways in which our experiences differ.

March 2004

Thursday, March 18, 2:00 - Note Special Day (Thursday)

Prof. Herbi Dreiner (Bonn Univ.)

"The Physik Show"

The Physik Show is an outreach program by Bonn Univ. Physics student volunteers. They work on a show for about 8 months, planning and building physics demonstrations, and then invite the public to six showings at the university. Prof. Dreiner will talk about the concept and then show movies and pictures from the showings.

Monday, March 15, 2:00

Wentai Liu (Dept. of Electrical Engineering, UCSC)

"Intraocular Retinal Prosthesis: A Biomimetic Microelectronic System"

We are developing an experimental retinal implant device in the hope of restoring some degree of vision to patients suffering from retinal diseases, primarily retinitis pigmentosa and macular degeneration. In these illnesses the rods and cones fail, but healthy ganglion cells survive to carry visual signals to the brain. The implant receives both signal and power by wireless transmission from an external unit and provides spatially/temporally electrical stimulation to the retina via a microelectrode array. This talk presents the development and status of a retinal prosthesis, a decade of work spanning from early through advanced generations along with characterizations of the hurdles and breakthroughs encountered in the wide array of clinical and engineering disciplines, which the project spans.

Monday, March 8, 2:00

Alexander Sher (SCIPP)

"New, high statistics measurement of the K+ -> pi0 e+ nu (Ke3) branching ratio by E865 at BNL"

I will describe the experiment, and talk about the measurement of the Ke3 branching ratio, and its relevance to the unitarity of the CKM matrix.

Monday, March 1, 2:00pm

Pablo Saz Parkinson (SCIPP)

"The USA Experiment: X-ray Astrophysics at SLAC"

The Unconventional Stellar Aspect (USA) experiment was launched in February of 1999 and operated for approximately 18 months. A collaboration between SLAC and NRL, USA was an X-ray detector sensitive in the 1-15 keV range and was SLAC's first foray into astrophysics. I will discuss the experiment, as well as some of its results.

February 2004

Thursday, February 26, 10:00am - Note: Special Day, Special Time  

John M. Beggs ( Indiana University , Dept. of Physics, Biocomplexity Institute)

" Information Storage and Avalanches in a Network of Cultured Cortical Neurons "  

The physiology of the cerebral cortex has been the subject of intense interest for many decades. This interest is perhaps driven by the desire to understand the mechanisms of higher cognitive functions that are dependent upon the cortex. While tremendous effort has been directed toward understanding cortical function at the cellular and large systems levels, much less experimental work has been done to uncover principles of neural interaction at the level of local cortical networks that comprise hundreds of neurons. We hypothesized that cortical networks were organized to accomplish at least three general tasks: Storing information, transmitting information, and maintaining network stability.

To investigate these issues, we cultured slices of rat cortex on 60 channel microelectrode arrays. Bursts of spontaneous electrical activity were recorded continuously after the cultures matured, and data were analyzed off line. Using this system, we found that spontaneous activity preferentially visited some network states more than would be expected by chance. These states were temporally precise and stable over a period of 10 hours, suggesting that they could be used by the network to store information. In addition, the number of electrodes activated in a burst of spontaneous activity was found to obey the same statistical rules that describe avalanches. Simulations of these avalanche dynamics showed that they were nearly optimal for information transmission and actually maintained network stability.

Thus, this work suggests that small cortical networks self-organize into a critical state that allows information storage, optimizes information transmission, and preserves stability. The principles governing cortical self-organization seem to be very general and share similarities with several non-biological phenomena like avalanches, earthquakes, nuclear fission and the spread of forest fires. Understanding emergent properties in these systems may therefore help us to understand emergent properties of cortical networks, and ultimately, the building blocks of cognition.

Monday, February 23, 3:00pm - Note: Special Time  

Richard Scalzo (LBNL)

"Observations of the Gamma-Ray Blazar W Comae with STACEE "  

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is ground-based telescope sensitive to high-energy gamma rays (> 100 GeV). It uses as its primary optic an array of solar heliostat mirrors, with total collection area of 2300 m 2 , to concentrate Cherenkov light from air showers initiated by gamma rays onto an array of photomultiplier tubes. The STACEE experiment was used to observe the AGN W Comae (ON+231) in the spring of 2003. Observations at other wavelengths strongly constrain theoretical models of gamma-ray emission from the relativistic jet in W Comae. These models predict significantly different fluxes of gamma rays above 100 GeV, depending on the types of particles responsible for the high-energy emission (electrons or protons). The results of the STACEE observations will be discussed within this context.

Tuesday, February 17, 10:30am - NOTE: Special Day, Special Time

Adrian Bevan (University of Liverpool)

"Measurement of the CKM angle alpha with the B-factories"

I'll be focusing on the recent time dependent CP asymmetry measurements in B0->pi+pi- in light of the recent publication by Belle. In addition to this I will briefly mention some of the prospects of measuring alpha in B0->rho+rho-.

Monday, February 2, 2:00pm

Sherwood Parker (University of Hawaii)

"Semiconductor track detectors - a brief history from World War II to the day after tomorrow”

This talk will review the underlying physics of semiconductor track detectors, some but not all, of the forms they have taken, and a bit of their history, starting from the work of a graduate student living in the Nazi-occupied Netherlands to the expected detectors and the pounding they will experience in the innermost regions of the planned high-intensity version of the 27 km Large Hadron Collider at CERN.

January 2004
Monday, January 26, 2:00pm

Gavin Nesom (SCIPP)

"FONT: Keeping the LC Colliding! (A Beam-Based Feedback System for the Linear Collider)"

The Feedback On Nanosecond Timescales (FONT) project aims to develop a beam-based feedback and correction system for stabilising the position of the nanometre-sized electron and positron bunches at the interaction point of the next-generation Linear Collider. We have built a prototype FONT system and tested it with a 170 ns long electron bunchtrain produced at the Next Linear Collider Test Accelerator at SLAC. We present the experimental results of the beam tests that were carried out at SLAC in September 2002 and more recently during November of 2003. The system operated as a feed-forward, with a single-pass delay loop feedback, and was able to provide a 10:1 beam position correction with a measured latency period of 66 ns. This represents a first demonstration of a Linear Collider type beam-based correction system that can operate on the relevant timescale of tens of nanoseconds.

Thursday, January 22, 10:30 pm [NOTE UNUSUAL DAY AND TIME!]

Stephen Libby (LLNL)

"Prospects for Investigating Nuclear Reactions Relevant to Astrophysics Using the National Ignition Facility"

The standard capsule design and other laser plasma targets at the National Ignition Facility offer the possibility of generating and studying thermal rates for significant astrophysical fusion reactions such as 3He(3He,2p)a, 7Be(p,g)8B, and 15N(p,a)12C. Presently, the "S" factors for these reactions are determined either by extrapolation from higher energy scattering data or by underground low event rate experiments (LUNA) on neutral atoms with concomitantly large screening corrections. The ability to directly generate thermal astrophysical fusion reactions will be complemented by "no frozen core" shell model predictions for light ion reactions. In addition, the expected fluence of neutrons from the main D + T -> a + n burn reaction can drive 10-20% of seeded spectator nuclei into excited states via (n,n') reactions. The ~2% 'minority' neutrons with E< 2 Mev due to D + D -> 3He + n and (n, n') can furthermore drive reactions pertinent to r, s, and p process heavy element nucleosynthesis including branches that pass through excited states with t > 10 ps. Both classes of reactions can be studied using particle spectroscopy and radiochemistry. Additionally, for the first time, it will be possible to measure the effects of plasma screening on thermonuclear reactions, addressing the extent of quantum corrections to Salpeter screening. Radiochemistry measurements of noble gas end species can be made with very high efficiency with only ~ 104-5 atoms required. Solid collection systems are being developed as well (with >108 atoms presently required). Because the capsule is essentially thin to neutrons, their reaction rate on advected sets of marker nuclei is a linear functional of the neutron source distribution. Determining this source function is thus computationally analogous to similar problems in medical imaging.

Monday, January 12, 2:00 pm

A. Grillo, H. Sadrozinski, A. Seiden (SCIPP)

"The Upgrade of the ATLAS Inner Detector for High Luminosity Operation at the LHC"

While the detectors for the Large Hadron Collider (LHC) projects are being assembled, CERN has plans for a future upgrade to raise the luminosity of the machine by a factor 10. The ATLAS Inner Detector (ID) being built now would not be able to operate and survive in the predicted radiation environment of an upgraded LHC. We will report from a workshop by the ATLAS Inner Detector community where the desirability and feasibility of an ID upgrade to an all semiconductor technology has been discussed.

December 2003
Wednesday, December 3, 10:00 am

Carter Hall (SLAC)

"EXO: a next generation double beta decay experiment"

The recent discoveries of neutrino mass in atmospheric, solar, and reactor neutrinos has generated renewed interestin the search for neutrinoless double beta decay. Double beta decay has the potential to reveal the absolute magnitude of the neutrino mass spectrum, and is closely related to the physics of grand unification. The EXO collaboration is developing an ambitious experiment to search for double beta decay in xenon-136 with neutrino mass sensitivities down to 0.01 eV. The key feature of EXO is our proposal to identify the final state barium-136 nucleus in real time through its unique optical spectroscopy, eliminating all radioactive backgrounds to the signal. I will describe the current state of the EXO R&D effort, and our plans for a 200 kg prototype experiment.

Wednesday, December 10, 10:00 am (note location: ISB 231)

Lisa Hunter (CfAO), Jamie Alonzo (COSMOS, invited), Hartmut Sadrozinski (SCIPP)

"Science Outreach at UCSC"

We will present several science outreach programs at UCSC, targeting K-12 students, their teachers and undergraduates. Students (both undergraduates and graduates), staff and faculty interested in outreach are encouraged to attend and get involved.

1) Hartmut Sadrozinski:

"SCIPP OUTREACH: Zapping the Teacher and BalloonFest"


2) Jamie Alonzo:

"COSMOS, UCSC high school science program"


3) Lisa Hunter, Director of Education, Center for Adaptive Optics (CfAO) and Scott Severson, Associate Research Astronomer, CfAO/UCO Lick

"Engaging High School Students in University Science" Center for Adaptive Optics (CfAO) Scientists have collaborated with education faculty and staff to design a wide range of educational activities at the high school and undergraduate level.


This seminar will present how the CfAO developed two courses that form the "Stars, Sight and Science" component of COSMOS, a UCSC high school science program. We will discuss questions such as: How can you get students involved in scientific investigations? How can you teach students from different grade levels at the same time? How do you decide what students should learn? How do you evaluate the success of the students and the program?

November 2003
Wednesday, November 5, 10:00 am

Dr. Alan Litke, Dr. Alexander Sher, Matthew Grivich (UC Santa Cruz)

"What does the eye tell the brain?"

We will describe a system aimed at understanding the language and processing employed by the eye to send information about the external visual world to the brain. We will present our first results on retinal processing based on experiments with live retinas.

1. Overview - Dr. Alan Litke

2. Organization of a Biological Image Detector - Matthew Grivich

3. Microstructure - Dr. Alexander Sher

Wednesday, November 12, 10:00 am

Joel Primack, Don Coyne et al. (UC Santa Cruz)

"Highlights from the INPAC and Kavli Institute Meetings"

The Inst. on Nuclear and Particle Astrophysics and Cosmology (INPAC) is a multi-campus Research Unit, with UCSC as one of the members. On Sat Oct. 18 the Kavli Institute for Astro-Particle Physics and Cosmology at SLAC has a kick-off meeting.

Attendees at both meetings will give brief reports on these particle astro activities.

Tuesday, November 18, 4:00pm - NOTE: Special Day, Special Time

Dr. Ghazal Geshnizjani (Brown University)

"Back-Reaction of Cosmological Perturbations on a Local Measure of the Expansion Rate"

We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. First, we consider a cosmological model in which matter is described by a single field. We analyze back reaction in a phase of scalar field-driven chaotic inflation. We find that the leading infrared terms contributing to the back reaction vanish when the local expansion rate is measured at either a fixed value of the scalar field, which is used as a clock or fixed value of proper time. Then we use coarse-grained method to calculate the additional effect due to the exit of modes from Hubble radios on proper time surfaces and we find that back-reaction effects don't vanish anymore. We also analyze back reaction in a phase of scalar field-driven chaotic inflation for two scalar field models and we find that it can be quite significant for inflation.

October 2003
Wednesday, October 8th, 10:00 am

Dr. David C. Williams

"Babar's Discovery of the DsJ(2317) and Confirmation of the DsJ(2458)"

BaBar's discovery of a narrow resonance in the mass spectrum near 2.32 GeV/c2 has spawned a renewed interest in charm spectroscopy in both experiment and theory. Subsequent measurements of a companion state in the gamma mass spectrum near 2.46 GeV/c2 has just increased the excitement. This talk presents a review of BaBar's analysis and a summary of results from other experiments. Theoretical implications are discussed.

Wednesday, October 15th, 10:00 am

Prof. David Smith (UC Santa Cruz)

"Nuclear-Line Astrophysics with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)"

RHESSI, a NASA Small Explorer satellite, was built to study the most powerful particle accelerator in the Solar System, the Sun -- which is also the most efficient, converting perhaps more than 50% of the flare energy to acceleration of particles to high energies.

RHESSI has made the first high-resolution measurements of gamma-ray lines from nuclei excited by accelerated ions. I will discuss these results and what they tell us about the physics of flares. In addition, RHESSI has observed nuclear lines from the radioactive decay of two isotopes> (26Al and 60Fe) in the inner Galaxy, shedding light on the ongoing process of nucleosynthesis. The 60Fe result is the first detection of this isotope, which has been anticipated for three decades.

Tuesday, October 28, 3:00 pm - NOTE: Special Day, Special Time

Brian Aagaard Petersen (Stanford University)

"Radiation Monitoring with Diamond Sensors in BaBar"

We are investigating CVD diamonds as a possible replacement for the silicon PIN-diodes currently used in the radiation monitoring and protection system of the BaBar experiment. Diamonds have a response to radiation comparable to that of silicon, but are significantly more radiation hard and have almost no leakage current. Two polycrystalline CVD diamonds were installed near the BaBar interaction region in October 2002 to test their behavior in a particle physics environment. They have been successfully operated for nine months and are now part of the BaBar radiation monitoring system. To study diamond radiation hardness, several sensors were placed downstream of the liquid hydrogen target in a high-intensity 45-GeV electron beam in End Station A at SLAC." Results from diamonds in BaBar and preliminary results from the End Station A beam test will be presented together with an overview of the status of diamond research in general.

Wednesday, October 29, 10:00 am

Prof. Mara Bruzzi (University of Florence)

"Material engineering issues for the development of ultra radiation hard semiconductor detectors at very high luminosity colliders"

Radiation hardening technologies for increasing the radiation resistance of semiconductor detectors are reviewed, in view of the possible upgrade of luminosity in LHC up to 10^35 cm-2s-1. The discussion will focus in particular to the material engineering methods carried out by the RD50 CERN Collaboration.