High Energy Physics Seminars
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2007/2008
Organizers: Ashutosh Kotwal and Kate Scholberg
Held in Duke Physics Room 278 (old Room 246) (Unless otherwise noted)Regular time for Fall '07 semester: Tuesday, 1 pm
October 30: Conor Henderson, MIT, 1 pm
NOTE ROOM CHANGE: seminar will be held in Room 298, the faculty lounge
Rather than focusing on particular new physics scenarios, we present a new approach where the entire high transverse momentum data collected by the CDF detector at the Fermilab Tevatron are searched for discrepancies relative to the Standard Model prediction.
A model-independent approach (Vista) considers the bulk features of the data, and a quasi-model-independent technique (Sleuth) focuses on the high-pT tails. Results of this global search for beyond Standard Model physics will be presented.
November 27: Szabi Marka, Columbia U., 1 pm
December 11: Kalanand Mishra,U. of Cincinnati, 1 pm
The CP-violating phase gamma of the quark-mixing Cabibbo-Kobayashi-Maskawa matrix plays a crucial role in placing constraints on the size of new physics contributions. One of the most effective method to measure this phase is to use the interference between the decays B -> D0 K and B -> D0bar K with D -> pi- pi+ pi0. We measure the magnitudes and phases of the components of the D0 -> pi-pi+pi0 decay amplitude. We apply these results to the CP violation analysis of the decay B+/- -> D(pi+pi-pi0)K+/-, where D(pi+pi-pi0) indicates a neutral D meson detected in the final state pi+pi-pi0, excluding KS pi0. The analysis makes use of 324 million e+e- -> BB events recorded by the BaBar experiment at the PEP-II e+e- storage ring. By analyzing the pi+pi-pi0 Dalitz plot distribution and the B+/- -> D(pi+pi-pi0)K+- branching fraction and decay rate asymmetry, we calculate parameters related to the phase gamma of the CKM unitarity triangle and constrain the allowed physical parameter space.
Regular time for Spring '08 semester: Monday, 2:30 pm
January 14: Jared Yamaoka, Rutgers University, 1:30 pm
I will present a measurement of the relative fraction of top-antitop (ttbar) events produced via gluon-gluon (gg) fusion to the total number of ttbar events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a artificial neural network (NN) to discriminate the gg fusion events. The NN was then used as a template to fit for the gg fusion fraction in data. Using a data sample with an integrated luminosity of 955 pb-1 collected with CDF, we find the fraction of gg fusion event in all ttbar events to be < 0.33 at the 68% confidence level and < 0.61 at the 95% confidence level.
February 11: David Gerdes, U. of Michigan, 2:30 pm
The discovery in 1998 that the expansion rate of the universe is accelerating came as a complete surprise. After reviewing some of the evidence for cosmic acceleration, I will describe the upcoming Dark Energy Survey (DES), a 5000 square degree optical survey of the southern sky. DES will measure cosmological parameters using four complementary techniques: Type Ia supernovae, weak gravitational lensing, baryon acoustic oscillations, and the growth of large-scale structure. These improved measurements will, perhaps, shed light on the mystery of the accelerating universe.
February 28: Michael Ramsey-Musolf, U. of Wisconsin, 4:15 pm
TUNL/Astro Seminar, Rm 130
Baryogenesis, Electric Dipole Moments, and the Higgs Boson
Explaining the origin of the cosmic matter-antimatter asymmetry is an important problem at the interface of nuclear physics with particle physics and cosmology. The dynamics of the Standard Model do not lead to successful baryogenesis, but new physics at the electroweak scale could do so. Searches for the permanent electric dipole moments of the neutron, electron, and neutral atoms may uncover the new CP-violation needed for electroweak baryogenesis, while studies of the Higgs boson and its cousins at the Large Hadron Collider could probe key aspects of the electroweak phase transition. In this talk, I discuss how these experiments at the precision and energy frontiers could provide important insights about the origin of the cosmic matter-antimatter asymmetry and highlight recent theoretical developments in addressing this problem.
March 17: Ayana Holloway, LBNL, 2:30 pm
When the Large Hadron Collider (LHC) begins operating later this year we will use the ATLAS detector and other instruments to make measurements of proton interactions at unprecedented energies. In LHC collisions we may also observe exotic processes that will help us resolve questions that the Standard Model leaves unanswered. In many scenarios the heavy and strongly interacting top quark is our best model for these new processes, and in others it plays a special role. I will review some recent experiments with top quarks that set the stage for LHC studies, and discuss the top quark's role in measurement strategies for understanding early data collected with the ATLAS detector.
March 31: Craig Dukes, U. of Virginia, 2:30 pm
The mu2e collaboration proposes to search for coherent, neutrinoless conversion of muons into electrons in the field of a nucleus with a sensitivity improvement of a factor of 10,000 over existing limits. Such a lepton flavor-violating reaction probes new physics at a scale unavailable by direct searches at either present or planned high energy colliders. The physics motivation for mu2e will be presented, as well as the design of the muon beamline and spectrometer. A scheme by which the experiment can be mounted in the present Fermilab accelerator complex will be described. Prospects for increased sensitivity using the Project X accelerator that is being proposed by Fermilab will be discussed.
April 21: Rebecca Surman, Union College, 2:30 pm
A potential astrophysical source of MeV neutrinos is a rapidly accreting disk around a stellar-mass black hole (AD-BH). In one possible formation mechanism, a subset of core-collapse supernovae will form an AD-BH rather than the canonical protoneutron star. We examine the neutrino fluxes emitted in this alternate scenario and investigate the consequences for galactic supernova neutrino detection. A second possible progenitor for an AD-BH is the collision of compact binaries. We examine the neutrino physics of this scenario starting with the results of a three dimensional numerical model of a black hole-neutron star merger. We calculate the neutrino and antineutrino fluxes emitted from the resulting AD-BH and discuss their impact on the system, focusing on their influence on the outflow nucleosynthesis.
April 28: Albert Young, NCSU, 2:30 pm
The goal of the UCNA project is to measure angular correlations in neutron decay using ultracold neutrons (UCN). In particular, we seek to measure the correlation between the electron emitted in beta-decay and the the neutron spin, proportional to the A coefficient. Measurements of the A coefficient play an important role in placing constraints on the standard model for the charged weak current from neutron decay; these constraints include providing critical data for unitarity tests of the CKM matrix, as well as placing limits on a variety of extensions to the standard model. UCN have several unique advantages for measurements of this kind, offering improvements over the typical cold neutron beam experiment in two key sources of systematic error: backgrounds (particularly if produced at a compact source coupled to a spallation target) and in the control of the neutron polarization. We present a status report on neutron beta-decay measurements and our first results from a preliminary measurement of the beta-asymmetry performed during the 2007 LANSCE run cycle. We performed measurements to characterize the UCN polarization and obtained 36 hours of beta-asymmetry data. We will also present our plans for the upcoming run cycle and how we plan to improve our sensitivity in the future.
May 19: Tim Tait, Argonne National Laboratory, 1:30 pm
I will discuss the idea that the right-handed top quark a is composite of some new strong force. I will show how current and future Tevatron measurements of t-tbar provide the best constraints on this idea, but that they are currently weak enough that some very big surprises are possible at the LHC. In particular, we find that the rate of production of four tops could be enhanced by as much as four orders of magnitude compared to the Standard Model rate, and I explore some possible methods to extract this challenging signal.
May 20: Bogdan Dobrescu, Fermilab, 1:30 pm
Physics at the TeV scale is currently 'terra incognita' awaiting explorations. The only hints are provided by electroweak symmetry breaking, and even they allow a wide range of phenomenological possibilities. I will give some examples of searches at the LHC that could lead to early discoveries.