SCIPP Seminar Archive

 

SCIPP Seminar Home

SPRING QUARTER 2011

Last updated:06/13/11

 
Friday August 26, 2011, 2:00pm
Location: ISB 310
Francesco Giordano (INFN and University of Bari, Italy)
Title: Fermi acceleration through the Fermi Mission

Abstract:

After three years of data taking, the Large Area Telescope (LAT), on the Fermi Gamma-ray Space Telescope, has detected about 100 pulsars, approximately ten pulsar wind nebulae, and roughly 20 supernova remnants. These energetic objects are adding exciting new information to help solve the puzzle of cosmic rays. I will discuss the GeV-TeV gamma-ray emission from many of these sources, now being resolved for the first time by the LAT. These observations are giving us precious details on the various populations of TeV-accelerated electrons and protons, as they interact, via the Fermi mechanism, with the environment where the gamma ray sources were born and are still evolving.

 
Tuesday June 28, 2011, 10:30am
Location: ISB 102
Daniel Brandt (SLAC/KIPAC/Stanford University)
Title: Detector Physics of the Cryogenic Dark Matter Search

Abstract:

In the research effort to determine the nature of dark matter, direct detection experiments such as the Cryogenic Dark Matter Search (CDMS) are attempting to detect the rare interaction of weakly interacting dark matter particles with conventional matter. I will outline the basic physics of dark matter detection with CDMS as well as the recent progress in developing and testing the next generation of CDMS detectors . The detector development process is supported by a Detector Monte Carlo (DMC) model which allows optimization of detector parameters across a vast parameter space. The DMC has to correctly model the anisotropic phonon propagation inside the detector crystal, as well as the propagation of slow electrons and holes. I will discuss the physics of the CDMS Monte Carlo model and our efforts to implement a full version of the DMC using the publicly available geant4 toolkit. This implementation will constitute the first condensed matter framework for geant4. Implementing our Monte Carlo model in geant4 ensures that the wider scientific community can benefit from our work. The geant4 toolkit was originally developed for high-energy physics to simulate the transport of particles through matter. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that with our current work, we may open up new avenues for applications in material science and condensed matter physics.

 
Tuesday June 21, 2011, 10:30am (NOTE: THIS SEMINAR HAS BEEN MOVED FROM MONDAY JUNE 6 & MONDAY JUNE 14-THANK YOU FOR YOUR PATIENCE)
Location: ISB 102
Nepomuk Otte (UCSC/SCIPP)
Title: The first detection of a pulsar above 100 GeV

Abstract:

Pulsars are rapidly spinning and magnetized neutron stars and powerful particle accelerators. How and where exactly the particles are accelerated is a mystery. Gamma-ray observations are a powerful tool to solve this long-standing puzzle. One of the paradigms in pulsar physics I grew up with was that no pulsar should be detectable above 100 GeV. With VERITAS, an array of four imaging atmospheric Chernekov telescopes, we have now detected pulsed emission from the Crab pulsar above 100 GeV, proving that this paradigm is wrong. I present this ground-breaking detection by VERITAS and put it into the context of present theoretical understanding. I close by discussing what this detection could possibly mean for future pulsar observations in the very-high energy gamma-ray band.

 
Tuesday June 7, 2011, 10:30am
Location: ISB 102
Federico Urban (Department of Physics & Astronomy, University of British Columbia)
Title: The luminous side of Dark Energy

Abstract:

Testing Dark Energy in any other way than indirectly inferring its existence and properties through its impact on cosmological structure formation and background evolution has always proven to be a major challenge. If Dark Energy however were somehow coupled to photons, we could envisage experiments literally casting light on its nature. In the QCD model of Dark Energy I will present, this is not only possible, but may help understanding some unexplained features of the sky on largest scales.

 
Tuesday May 31, 2011, 10:30am
Location: ISB 102
Yue Zhao (Rutgers)
Title: Super particles at the LHC: Early searches and mass measurements

Abstract:  

This talk has two parts. In the 1st half of the talk, we focus on the early searches for new physics at the LHC. We present a complete classification of multi-lepton signatures, that provides a framework for an exclusive multi-lepton channel search. This formed the basis for a CMS search for new physics in the Fall 2010 data. We study slepton co-NLSP and stau NLSP scenarios as examples of such multi-lepton physics. We also study the di-photon + MET signature in a Bino-like neutralino NLSP scenario. We present benchmarks, estimate the reach and set limits for different superparticles. In the second half of the talk, we study a new mass measurement technique which may be applied to a signal with displaced vertices or displaced tracks, this can occur with low scale SUSY breaking. We find that these exotic features can provide us additional handles when reconstructing events, and one can extract part of the mass spectrum with only a few events.

 
Tuesday May 24, 2011, 10:30am
Location: ISB 102
Warren Essey (UCB)
Title: Secondary photons and neutrinos from distant blazars and the intergalactic magnetic fields

Abstract:

Secondary photons and neutrinos produced in the interactions of cosmic ray protons and gamma rays emitted by distant Active Galactic Nuclei (AGN) with the photon background along the line of sight can reveal a wealth of new information about the intergalactic magnetic fields (IGMF), extragalactic background light (EBL), and the acceleration mechanisms of cosmic rays. The secondary photons may have already been observed by gamma-ray telescopes. With the inclusion of secondary photons the current upper limits on the extragalactic background light are significantly weakened and new limits are set for the intergalactic magnetic fields for a wide range of cosmic ray and gamma ray models. The secondary neutrinos also improve the prospects of discovering distant blazars by IceCube. Ramifications for the cosmic backgrounds, magnetic fields, and AGN models will be discussed.

 
PLEASE NOTE: Special SCIPP Seminar Day and Time!
Thursday May 12, 2011, 12:30pm
Location: ISB 102
Keith Olive (University of Minnesota)
Title: A Frequentist Approach to Supersymmetric Models - post LHC2010 and Xenon100

Abstract:

After a brief introduction to constrained supersymmetric models- including models based on minimal supergravity, predictions for dark matter detection and other low energy observables based of a purely frequentist Markov Chain-Monte Carlo analysis are presented. The impact of the 2010 LHC data as well as the recent Xenon100 results are contrasted to these predictions.


 
Tuesday May 3, 2011, 10:30am
Location: ISB 102
Scott Thomas (Rutgers)
Title: Results from the First Run of the Large Hadron Collider and the Last Run of the Tevatron

Abstract:

TBA

 
Wednesday April 27, 2011, 10:30am
Location: ISB 310
Felix Rosenbaum, Risk Manager at Swiss Re(Former SCIPP postdoc)
Title: Mathematical Concepts in the Insurance IndustryTALK

Abstract:

So, you have car insurance but insurance is boring!  Is it really that simple? How much would you then charge if you wanted to insure your  friend's car?  A short introduction to insurance math will show you that things aren't that simple, and that in case of insurance for natural catastrophes, the starting point is a physical event.  You will see how insurance companies do joint research with universities and if climate change has an influence on natural catastrophes.

 
Tuesday April 26, 2011, 10:30am
Location: ISB 102
Curt Callan (Princeton University)
Title: Theoretical physics in cellular biology: a few case studies
Abstract:

I would argue that the study of living matter needs the attention of people who think like theoretical physicists. I will make some general remarks about why this might be so and then walk you through a problem (or two) where physical and mathematical principles lead to insights into an important area of biology.

 
Thursday April 14, 2011, 12:30pm
Location: ISB 310
John March-Russell (Oxford University)
Title: The Baryon-Dark Matter Connection

Abstract:

TBA

 
Tuesday April 5, 2011, 10:30am
Location: ISB 102
Amy Furniss (UCSC-SCIPP)
Title: VERITAS Very High Energy Gamma-ray Observations of Galaxies VERITAS

Abstract:

Remarkable progress has been made in very high energy (VHE; E > 100 GeV) gamma-ray astrophysics in the last decade. The VHE source catalog has increased tenfold, with a wide variety of source classes, and includes more than 30 extragalactic objects. Currently, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) has made observations of numerous source candidates, both galactic and extragalactic, including more than 100 galaxies. The last 18 months of observations are especially noteworthy as they have been completed in a new array configuration, following the relocation of one of the four 12 meter telescopes. This new configuration has yielded a significant increase in the VERITAS sensitivity to gamma-ray sources above 100 GeV, resulting in several new source detections in the first few months of operations alone. To date, the VERITAS extragalactic source catalog includes various AGN, the radio galaxy M87 and the starburst galaxy M82 (the latter was detected using data obtained under the old array configuration). Highlights from the VERITAS extragalactic observation program will be presented, with a focus on the most recent discoveries.

 
Tuesday March 29, 2011, 10:30am
Location: ISB 102
Fulai Guo (UCSC-UCO/Lick Observatory)
Title: Fermi Bubbles: the Origin and Implications

Abstract:

The Fermi Gamma-ray Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 degrees above and below the Galactic Center and have sharp edges. It is difficult to explain the bubbles in many of the standard ways, e.g., cosmic ray electrons produced by supernova shocks in the Galactic plane or dark matter annihilations. Using numerical simulations with a self-consistent treatment of the dynamical cosmic ray-gas interaction, we show that the bubbles are likely the remnant of a powerful AGN jet event from the Galactic center, which happened about 1 - 2 Myr ago, lasting for around 0.1 - 0.5 Myr and releasing a total energy of a few 10^{57} erg. The sharp edges of the bubbles imply that cosmic ray diffusion across the bubble surface is strongly suppressed. The jet activity induces a strong shock, which heats and compresses the ambient halo gas, explaining the ROSAT X-ray emission features surrounding the bubbles. Finally, I will briefly talk about other possible evidence and implications of this event.

 

 
Tuesday March 22, 2011, 10:30am
Location: ISB 102
Jennifer Siegal-Gaskins (Ohio State)
Title: Searching for dark matter and astrophysical sources with gamma-ray anisotropies Siegel-Gaskins Slides_03_22_11

Abstract:

The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. Recent studies have considered the angular power spectrum and other anisotropy metrics as tools for identifying contributions to the diffuse emission from unresolved gamma-ray source classes, including extragalactic and Galactic dark matter as well as various astrophysical source populations. I'll review these results, focusing on how anisotropy analysis could extend the sensitivity of current indirect dark matter searches. I'll also discuss preliminary results from an angular power spectrum analysis of the Fermi-measured diffuse gamma-ray emission, and the implications of this measurement for various gamma-ray source populations.