Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session T3: Invited Session: DNP Prize Session |
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Sponsoring Units: DNP Chair: Berndt Mueller, Duke University Room: Plaza E |
Monday, April 15, 2013 3:30PM - 4:06PM |
T3.00001: Bonner Prize Talk -- First Laboratory Observation of Double Beta Decay Invited Speaker: Michael Moe Although we are awash in neutrinos, we remain ignorant of some of their fundamental properties. We don't know their masses. We don't know whether ``anti-neutrinos'' are really distinct particles. Double beta ($\beta \beta )$ decay offers a handle on these questions if we can observe the energy spectrum of the two emitted electrons, and determine whether or not they share their energy with two neutrinos. Seeing neutrinoless (0$\nu )$ decay would solve some enduring puzzles. The power of the process to elucidate the neutrino was recognized in the 1930's, but $\beta \beta $ decay would be exceedingly rare and difficult to detect. Unsuccessful laboratory searches had been going on for 25 years when the UC Irvine group began its first experiment with a cloud chamber in 1972. After some background for the non-expert, and a snapshot of the theoretical and experimental milieu at the time, the talk will begin with the reasons for choosing a cloud chamber, and the taming of its balky and idiosyncratic behavior. The talk will end with the first definitive observation of two-neutrino (2$\nu )\beta \beta $ decay of $^{\mathrm{82}}$Se in the vastly superior time projection chamber (TPC) in 1987. Discouragement through the tortuous 15-year interval was relieved by occasional victories. Some I will illustrate with revealing cloud-chamber photographs. We learned many things from this primitive device, and after seven years we isolated an apparent $\beta \beta $ decay signal. But the efficiency of the trigger was small, and difficult to pin down. Estimating 2.2{\%}, we were way low. The resulting ``short'' $^{\mathrm{82}}$Se half-life of 1 x 10$^{\mathrm{19}}$ years was suspect. New technology came to the rescue with the invention of the TPC. Experience with the cloud chamber guided our design of a TPC specifically for $\beta \beta $ decay. The TPC was built from scratch. Its long, steep learning curve was also punctuated with little triumphs. A memorable moment was the first turn-on of a portion of the chamber. So long ago, this all seems rather quaint, but through ample use of photographs and anecdotes it makes and interesting story. As a digital device, the TPC made data acquisition and analysis orders of magnitude simpler and faster. After seven years of massage, the TPC yielded good evidence for 2$\nu $ decay of $^{\mathrm{82}}$Se with a half-life near 10$^{\mathrm{20\thinspace }}$ years. While the 0$\nu $ mode was not in evidence, finally seeing $\beta \beta $ decay in the laboratory created optimism about an eventual 0$\nu $ discovery. [Preview Abstract] |
Monday, April 15, 2013 4:06PM - 4:42PM |
T3.00002: George E Valley Prize Talk: Measurements of phi-meson production and the observation of antihypertriton in Au$+$Au collisions at RHIC Invited Speaker: Jinhui Chen Collisions of heavy nuclei at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) briefly produce hot and dense matter that has been interpreted as a quark gluon plasma (QGP) . The energy density of the plasma is similar to that of the universe a few microseconds after the Big Bang. This plasma contains roughly equal numbers of quarks and antiquarks. As a result of the high energy density of the QGP phase, many strange-antistrange quark pairs are liberated from the quantum vacuum. The plasma cools and transitions into a hadron gas, producing nucleons, hyperons, mesons, and their antiparticles. The phi-mesons are ideal experimental probe to explore the QGP evolution dynamics. They are predicted to have relatively small hadronic interaction cross sections. Thus those phi-mesons carry the information directly from the hadronization stage with little or no distortion due to hadronic rescattering. In this talk, I will present the phi-meson production in Au$+$Au collisions at center-of-mass energy of 200GeV. Energy and system size dependence of the phi yields at mid-rapidity will be discussed. Centrality and transverse momentum dependence of the phi elliptic flow and nuclear modification factor will be presented. Properties of strange quarks in the bulk matter at hadron formation will be discussed. I will also present the details of the antihypertriton observation from the STAR experiment. Physics implication related to the QGP formation and hyperon-nucleon interaction from the data will be discussed. [Preview Abstract] |
Monday, April 15, 2013 4:42PM - 5:18PM |
T3.00003: Novel Developments in Instrumentation for PET Imaging Invited Speaker: Joel Karp Advances in medical imaging, in particular positron emission tomography (PET), have been based on technical developments in physics and instrumentation that have common foundations with detection systems used in other fields of physics. New detector materials are used in PET systems that maximize efficiency, timing characteristics and robustness, and which lead to improved image quality and quantitative accuracy for clinical imaging. Time of flight (TOF) techniques are now routinely used in commercial PET scanners that combine physiological imaging with anatomical imaging provided by x-ray computed tomography. Using new solid-state photo-sensors instead of traditional photo-multiplier tubes makes it possible to combine PET with magnetic resonance imaging which is a significant technical challenge, but one that is creating new opportunities for both research and clinical applications. An overview of recent advances in instrumentation, such as TOF and PET/MR will be presented, along with examples of imaging studies to demonstrate the impact on patient care and basic research of diseases. [Preview Abstract] |
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