Joint High Energy Physics/Theory Seminars
HEP/theory seminar mailing list
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2008/2009
Organizers: Ashutosh Kotwal, Kate Scholberg and Tom Mehen
Held in Duke Physics Room 278 (old Room 246) (Unless otherwise noted)Regular time for Fall '08 semester: Tuesday, 2 pm
September 23: Paul Frampton, UNC, 2 pm
In a simplified renormalizable model where the neutrinos have PMNS (Pontecorvo-Maki-Nakagawa-Sakata) mixings tan$^{2} \theta_{12} = {1/2}, \theta_{13}=0, \theta_{23} = \pi/4$ and with flavor symmetry $T^{'}$ there is a corresponding prediction where the quarks have CKM (Cabibbo-Kobayashi-Maskawa) mixings tan$2 \Theta_{12} = \frac{\sqrt{2}}{3}, \Theta_{13}=0, \Theta_{23} =0$.
October 15: Esben Klinkby, Duke U., 1:30 pm
The topic of the seminar will be the content of my recently submitted thesis which concerns itself with the ATLAS experiment, and in particular the Transition Radiation Tracker (TRT) sub-detector. Focus is put on the the simulation of the detector and the comparison of the simulation with test-beam data, as well as with data collected during the commissioning phase using cosmic muons.
Also discussed is the W mass measurement at the ATLAS experiment - a key measurement to understand the origin of mass. By precisely measuring the W boson mass, the allowed mass range for the Higgs boson can be constrained, both within the Standard Model and in its various extensions. Thus, regardless of the results of the Higgs search, a precise determination of the W mass is of paramount importance, and in this seminar and notably in the thesis on which it is based, methods are presented aiming at measuring the W mass to the highest possible precision with the ATLAS experiment.
The thesis it itself can be found here.
November 18: Mike Ronquest, UNC, 2 pm
This talk presents a search for direct CP violation in the decay K_{L,S} -> pi+pi-gamma. This direct CP violation is expected to be identified by the observation of the direct emission electric dipole (E1) photons from the K_{L} decay. Since this process is small compared to the dominant M1 emission term, as well as the inner bremsstrahlung E1 photon emission process, observing the photon's energy and direction is not enough to isolate the process. Also observing the time evolution of the photon emission from decays in a beam of coherent K_{L} and K_{S} yields a powerful tool with which to search for this rare process. Using data collected by the KTeV experiment at Fermilab, we apply a theory describing the strength and characteristics of the various processes which are responsible for the decay: inner bremsstrahlung, M1 direct photon emission and finally E1 direct photon emission. The E1 direct photon emission process is split into two parts: a part that violates CP symmetry indirectly (mixing type CP violation) and a part that violates CP directly (via decay amplitudes ). The data consist of observed decays from KTeV's coherent K_{L} and K_{S} beam, as well as KTeV's pure K_{L} beam.
November 25: Roxanne Springer, Duke U., 2:30 pm
At low energies, parity violation in NN scattering is described by an effective field theory (EFT) that includes only contact interactions. I will describe this EFT, how it improves upon the standard (non-physical) description, how it echoes an ancient treatment, and how its predictions compare to existing (presently under-constraining) measurements.
December 2: Kendall Mahn, Columbia U., 2 pm
To search for neutrino oscillations in the few eV2 Dm2 region, the MiniBooNE experiment can either look for electron neutrino appearance or muon neutrino disappearance. Disappearance measurements are an uniquely sensitive probe of oscillations to sterile neutrinos or other exotic processes such as neutrino decay. The 74% pure, high statistics CCQE muon neutrino sample in MiniBooNE can be used to make sensitive searches for disappearance of muon neutrinos and for the first time antineutrino disappearance in the few eV2 Dm2 range. By combining MiniBooNE with SciBooNE, a near detector recently added to the beamline, even better sensitivity to disappearance can be achieved. Results for the MiniBooNE neutrino disappearance measurement will be presented along with the prospects for antineutrino and combined MiniBooNE/SciBooNE measurements.
December 11: Mark Kruse, Duke U., 3 pm
We report on a recent study of events collected at CDF from a sample requiring at least two muons. The production cross section and kinematics of events in which both muons are produced inside the beam pipe (within a radius of 1.5cm) are well explained by known processes, which is dominated by b-bbar production. When at least one muon is produced outside of the beam pipe, we are presently unable to explain the rate and characteristics of the events remaining after accounting for the known processes. These events offer a plausible explanation to previous inconsistencies related to b-bbar production and decay. We are continuing with various longer-term studies in an endeavour to better understand the source of these events.
Regular time for Spring '09 semester: Monday 3 pm
January 28: Hitoshi Murayama, IPMU/UC Berkeley, 2 pm
Note non-standard day/time
We all hope to discover exciting new physics at Tevatron and LHC. If we find new particles, however, it will not be clear for some time what we have discovered. One of the key measurements is determination of spins for each new particle, which is notoriously difficult task at hadron colliders. Many of the techniques in the literature assume model framework and see if it is consistent with the data, a potentially circular methodology. I discuss a new technique to obtain information on spin of new particles without any model assumptions.
March 2: Zoltan Ligeti, LBNL, 4 pm
Motivated by a recent controversy about interpreting a surprising signal at GSI as a measurement of neutrino mixing parameters, we revisit the theory underlying neutrino oscillations. The neutrino state produced by a weak decay is usually portrayed as a linear superposition of mass eigenstates with, variously, equal energies or equal momenta. We point out that such a description is incomplete, that in fact, the neutrino is entangled with the other particle or particles emerging from the decay. We offer an analysis of oscillation phenomena involving neutrinos (applying equally well to neutral mesons) that takes entanglement into account. Thereby we present a proof of the universal validity of the oscillation formulae ordinarily used. In so doing, we show that the departures from exponential decay reported by the GSI experiment cannot be attributed to neutrino mixing. Furthermore, we demonstrate that a proposed "Mossbauer" neutrino oscillation experiment, while technically challenging, is correctly and unambiguously describable by the usual oscillation formalae.
March 9: Anyi Li, U. of Kentucky, 3 pm
Whether QCD has a critical point at non-zero baryon density is not only an experimental interest but also a challenge for the theory. We use lattice simulations based on the canonical ensemble approach to explore this interesting region. This approach avoids overlap problem and sign problem above $80\%T_c$. We scan the phase diagram of three flavor QCD in quark number and found an ``S-shape'' structure in $\mu_B/T$ verse baryon number plane that indicates a first order phase transition at finite volume. It exists in the region where $T \sim 82\% T_c$, baryon number $\sim 13$ to $15$ and $\mu_B/T \sim 4$. With these ``S-shape'' structures at three different temperatures, we determine the phase boundary by Maxwell construction. Preliminary results for the location of critical point are also presented.
March 16: Fred Olness, SMU, 3 pm
W/Z/Higgs Production at the LHC & PDF Uncertainties
The broad kinematic reach of the Large Hadron Collider (LHC) increases the role of the heavier quark components (e.g. s,c, & b); this has important implications for the LHC "benchmark" processes such as W and Z boson production which are a crucial stepping stone to the Higgs discovery. We review the recent data as well as theoretical advances which are enable an enhanced analysis of the upcoming LHC data.
March 19: Pasha Murat, 3 pm
Note non-standard day and time
From many points of view supersymmery (SUSY) provides one of the most promising extensions of the Standard Model. It is usually assumed that supersymmeric models conserve R- or, matter, parity. However, if R-parity was not conserved, experimental landscape of the SUSY searches would have to change dramatically.
With supersymmetric particles allowed to decay into their SM partners, the lightest supersymmetric state would not necessarily have to be stable and large missing energy would no longer be a critical signature of the SUSY particle decays.
In my talk I will discuss current phenomenological constraints on the R-parity violating models and focus on the experimental searches for R-parity violation at the Tevatron collider at Fermilab.
April 8: Ian Shipsey, Purdue U., 1:30 pm
Note non-standard day and time
Recent technological advances have made it possible to carry out deep optical surveys of a large fraction of the visible sky. Such surveys enable a diverse array of astronomical investigations including: the search for small moving objects in the solar system, studies of the assembly history of the Milky Way, the establishment of tight constraints on models of dark energy using a variety of independent techniques and the exploration of transient sky. The Large Synoptic Survey Telescope (LSST) is the most ambitious project of this kind that has yet been proposed. With an 8.4 m primary mirror, and a 3.2 Gigapixel, 10 square degree camera, LSST will provide nearly an order of magnitude improvement in survey speed over all existing surveys, or those which are currently in development. Over its ten years of operation, LSST will survey 20,000 square degrees of the sky in six optical colors down to 27th magnitude. At least a thousand distinct images will be acquired of every field, enabling a plethora of statistical investigations for intrinsic variability and for control of systematic uncertainties in deep imaging studies. In this talk some of the science that will be made possible by the construction of LSST, especially dark energy science, and a brief overview of the technical design will be given.
April 27: Donal O'Connell, Institute for Advanced Study, 2:30 pm, Room 278
Note non-standard time
I will discuss an extension of the standard model of particle physics motivated by the hierarchy problem. This extension, the Lee-Wick standard model, is based on ideas of T.D. Lee and G. Wick. The theory has some successes but there is a price to pay. I will comment on the successes as well as on the issues facing the theory and the resolution of some of them. The physics is exotic but nevertheless the model reduces to the standard model and appears to evade current experimental bounds.
April 27: Michael Creutz, BNL, 4 pm, Room 298
Note non-standard time and place
April 28: Albert Erwin, U. of Wisconsin, 3 pm, Room 298
Light refreshments at 2:30 pm
Note non-standard day, time and place
We have studied particle production in a spectrometer which is perpendicular to the p-pbar colliding beam at Fermilab. The collected data provide 8 particle cross sections, 3 momentum spectra, and overall produced particle multiplicity per event. When cross sections are corrected for secondary contamination from higher mass decays, the primary cross sections per spin state follow closely a Boltzman distribution exp(-m/kT). The same distribution with the same kT value also describes e+e- cross sections in the charm sector up to the J/Psi mass. Explanations stress the imagination. We examine string theory with Hawking radiation, statistical gas models with Bose condensation of pions, and the exponential density of mass states in the Hagedorn bootstrap model.