Nuclear/High Energy Seminar Abstracts
Spring 2007
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New generations of silicon photomultipliers (SiPMs) have single photo-electron resolving capabilities and will consequently phase out phototubes, their larger, more expensive counterparts. The silicon photomultiplier will lead to significantly more economical detectors for scintillator calorimetry and for devices in other scientific arenas such as space and medicine. The International Linear Collider (ILC) is an electron-positron collider that intends to reach energies as high as a terraelectronvolt, five times that of current colliders. These high gain, low bias devices are impervious to radiation and magnetic fields, making them an optimal choice for photon detecting devices. We have been examining and evaluating the performance characteristics of silicon photomultipliers and have shown that the resolution surpasses that of phototubes. Due to their simplicity, low power requirements, cost-effectiveness, and ease of calibration, silicon photomultipliers are an inevitable replacement for the outdated phototube.
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The recent surprises in neutrino physics have largely been discovered using neutrinos from astrophysical sources and from nuclear reactors. To exploit the opportunities we have found for future studies of neutrinos, the neutrino community is developing a staged program culminating in multi-megawatt accelerator neutrino sources and megaton neutrino detectors. The prize is illumination of the flavor structure of neutrinos and possible evidence that the matter-antimatter asymmetry in the Universe has its origin in neutrinos.
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Due to the short lifetime of the medium produced at RHIC, probes of the medium must come from the medium itself. To study bulk properties of the medium, the probe must interact with the medium strongly enough to be affected by the final state properties, but not so strongly that the probe is insensitive quantitatively to the parameters describing the medium. While the medium is nearly transparent to electromagnetic probes, and nearly opaque to light hadrons, hadrons containing heavy quarks serve as an intermediate probe capable of measuring bulk properties such as viscosity and transport coefficient. Th experimental and theoretical challenges involved in the measurement and interpretation of heavy flavor spectra at RHIC are outlined, and recent results from data from Au+Au collisions at sqrt(s_NN)=200 GeV collected by the PHENIX experiment are shown. |
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I will discuss the HERMES spectrometer, which we use to measure semi-inclusive deep-inelastic scattering. This process can be used to "flavor tag," a technique which correlates the partonic structure of the proton with the flavor of final-state detected hadrons. Within the QCD improved parton model we can extract the light quark valence distributions as well as the light sea asymmetry. The first subject is a test of the validity of the factorization assumption in the HERMES kinematic region. The second result is a measurement of an extremely interesting phenomenon that is not predicted by perturbative QCD and is an important verification of the original E866 Drell-Yan result from an entirely different physical process. The current analysis applies the latest HERMES inefficiency and radiative correction techniques and encompasses a significant statistical improvement over the previous HERMES publication.
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A rare decay B->J/psi Lambda pbar is searched with Belle data. In the search we use two new analysis variables to isolate B mesons. I will also introduce BESII and BESIII drift chamber tracking software, especially BESIII track finding software, in which the method is fresh in some ways.
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The ultimate existence of matter in the universe depends on a tiny imbalance between the physical interactions of normal, everyday matter and those of anti-matter. Non-zero CP Violation, a measure of the matter-anti-matter asymmetry, has now been observed in B meson decays--though not on levels sufficient to explain the observed domination of matter over anti-matter. In this seminar, I present recent experimental results from the BaBar Collaboration measuring CP Violation in rare, charmless B meson decays and discuss the possibility of using these measurements as a window into new, non-standard model, physics effects.
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The MiniBooNE neutrino oscillation experiment was motivated by evidence reported by LSND for oscillations at the delta m**2 squared scale around 1 eV**2. Oscillations at this scale cannot be reconciled with the results of atmospheric, solar, reactor, and other accelerator experiments without introducing at least a fourth neutrino mass or other novel physics. MiniBooNE tests LSND using a substantially different experimental technique, including a higher energy beam and detection of oscillations through a different neutrino interaction channel. Initial results for the muon neutrino to electron neutrino appearance search will be presented.
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The Main Injector Particle Experiment at Fermilab is an open geometry multiparticle spectrometer capable of measuring hadronic particle production using 6 beam species on a variety of targets. MIPP is capable of measuring and identifying charged particles in the final state with nearly complete acceptance. MIPP has so far acquired 20 million events which are being analyzed. We will describe the status of the analysis. MIPP has proposed a scheme to speed up the data acquisition by a factor of 100 and obtain high quality data on a variety of targets that will greatly improve our knowledge of hadronic spectra and enable us to simulate hadronic showers with much greater accuracy. The possibility of tagged neutral beams will be discussed and their impact on the detector R & D for the International Linear Collider.
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