Nuclear/High Energy Seminar Abstracts
Spring 2009
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We review both analytical and numerical approaches for studying Pair Production from strong external fields and the backreaction problem for the external field in QED and QCD and discuss various as yet unresolved issues in looking for experimental signatures in Heavy Ion colliders. |
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The observation of jet quenching in ultra-relativistic heavy ion collisions at RHIC demonstrates significant energy loss of fast partons when passing through the created medium. Correlations between final-state particles at high transverse momentum (pT > 4.0 GeV/c) allow for the study of parton energy loss via suppression of back-to-back pairs. Furthermore correlations between intermediate pT particles (1.0 < pT < 4.0 GeV/c) may contain evidence of medium response to the passage of fast partons. Comparison of these measurements with baseline measurements in proton-proton collisions show strong modification to the correlation shape and pair yields. Two structures unique to heavy ion collisions are found, both extended in Delta-eta, one centered at Delta-phi = 0 rad ("ridge'') and the other occurring at |Delta-phi| approximately 1.1 rad ("shoulder"). In this review of jet probes, discussion at high pT will focus on energy loss mechanisms and the properties of back-to-back pairs. The status of new measurements at high pT with respect to reaction plane that should help discern the role of "corona" vs "punch-through" production will be presented. Discussion at intermediate pT will include a technical review of advanced background normalization techniques critical to confidence in medium response shape and yield extraction. "Shoulder" and "ridge" properties and an overview of competing theoretical models for each will be presented. A possible explanation for the similarities found between "shoulder" and "ridge" pairs under a single production mechanism will be given. Future directions for correlation measurements will also be discussed. |
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I will review the theoretical status of staggered Lattice QCD with the "fourth-root trick." In this regularization, a separate staggered fermion field is used for each (light) physical flavor. The inherent, unwanted four-fold multiplicity of staggered fermions is removed by taking the fourth root of the staggered determinant. At nonzero lattice spacing, the resulting theory is nonlocal and not unitary. Nevertheless, there are now strong arguments that this disease is cured in the continuum limit. In addition, the approach to the continuum limit can be understood in detail in the framework of staggered chiral perturbation theory. |
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MINOS is a long baseline neutrino oscillation experiment designed to make precision measurements of the neutrino mixing parameters associated with the atmospheric neutrino mass splitting. A high power muon neutrino beam is generated at the Main Injector (NuMI) facility at Fermilab and measured at two large detectors, one located at Fermilab and the other in the Soudan mine in northern Minnesota at a distance of 735km away. In addition to the main muon-neutrino disappearance measurement, it is possible for MINOS to make the first measurement of the mixing angle related to electron-neutrino appearance. This talk will describe methods of particle identification of electron neutrinos and several of the techniques based on non-oscillated data at the near detector which are used to estimate the background contributions to this analysis. |
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We construct a model based on SU(5) combined with the double tetrahedral group T' as the family symmetry. Due to the presence of the doublet representations in T', there exist complex CG coefficients, leading to explicit CP violation in the model, while the Yukawa couplings and the vacuum expectation values of the scalar fields remain real. The predicted CP violation measures in the quark sector are consistent with the current experimental data. The leptonic Dirac CP violating phase, delta_{ell}, is predicted to be ~ - arccos(2/3), which turns out to be the value needed to account for the difference between the experimental best fit value for the solar mixing angle and the tri-bimaximal mixing matrix prediction. |
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The Daya Bay Reactor Anti-Neutrino Experiment is a neutrino oscillation experiment designed to observe and measure the neutrino mixing angle theta_13. The sensitivity goal is 0.01 in sin^2 theta_13 at the 90% confidence level, a significant improvement over the current limit. This will be accomplished by measuring the relative rates and energy spectra of reactor electron antineutrinos with multiple detectors positioned at different baselines. Civil construction is currently under-way and construction of detector systems is beginning. Commissioning activities should begin in 2010 with a three-year data run thereafter. |
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In this talk, I will present the latest published results fromthe Sudbury Neutrino Observatory (SNO). This Heavy-Water (D20) Cerenkov detector was designed to resolve the solar neutrino problem; since Ray Davis' experiment in the 1960s, there had been a discrepancy between the measured solar neutrino flux and that predicted by the solar model. The SNO experiment conclusively showed in 2001 that solar neutrinos, produced in the electron flavour, transform into muon and tau flavours on their way to earth. The detector was able to measure the electron flavour flux through a charged-current reaction, whereas the total flux of neutrinos was measured independently through a neutral-current reaction that produced a neutron. The SNO experiment was performed in three phases defined by different ways of detecting the neutron. In the first phase, the neutrons were detected by capture on deuterium, in the second phase, two tons of salt (NaCl) were added to exploit the high cross-section for neutron capture on 35-Cl, and finally, in the third phase, 40 proportional |