Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session B4: To the Heart of the Matter: Frontiers in Nuclear Science |
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Sponsoring Units: CSWP DNP Chair: Gail McLaughlin, North Carolina State University Room: Marriott Tampa Waterside Grand Salon C/D |
Saturday, April 16, 2005 10:45AM - 11:21AM |
B4.00001: Doubly magic character of $^{78}$Ni - complex studies of simple nuclei Invited Speaker: The neutron-rich, doubly-magic nucleus $^{78}$Ni and its
neighbors are candidates for benchmarks that test nuclear
structure models far from stability. According to shell-model
calculations with effective interactions[e.g., 1], the large
neutron excess in nuclei near $^{78}$Ni is expected to modify
single-particle energies, which may lead to the weakening or
disappearance of traditional shell-gaps. Moreover, these nuclei
lie in a region of interest for nuclear astrophysics, since
r-process nucleosynthesis is supposed to be initiated close to
$^{78}$Ni [2]. Very little is known empirically about $^{78}$Ni.\\
Several experimental studies on neutron-rich Z$\sim$28 and
40 |
Saturday, April 16, 2005 11:21AM - 11:57AM |
B4.00002: What Have We Learned from the Nucleon Spin Structure? Invited Speaker: Since the 1980s, the development of polarized electron sources and polarized target techniques has brought the experimental study of the nucleon into a new era. The spin structure of the nucleon has been explored with polarized electron scattering. Now twenty years have passed. What have we learned from the data? Do they agree with predictions from quantum chromo-dynamics (QCD), the theory for strong interactions? And what about predictions from constituent quark models? I will start from a brief introduction to the study of hadron structure using lepton deep inelastic scattering, and give an overview of world data and what we have already learned about nucleon structure. Then I will present results from a precision experiment completed at Jefferson Lab on the study of the neutron spin in the valence quark region, and discuss the surprising implication of these results. [Preview Abstract] |
Saturday, April 16, 2005 11:57AM - 12:33PM |
B4.00003: Nuclear collisions at the Relativistic Heavy Ion Collider - exploring the phase diagram of QCD Invited Speaker: By colliding nuclei at extreme energies, the relativistic heavy ion collider (RHIC) hopes to briefly recreate in the laboratory a deconfined plasma of quarks and gluons, similar to the conditions in the early universe shortly after the Big Bang. Careful scrutiny of the data collected from the first four years of running show that a dense state of matter inconsistent with ordinary color neutral hadrons is formed in central Au+Au collisions. I will review some of the major pieces of evidence from the four RHIC experiments which support this conclusion and discuss some of the open questions remaining to be answered with current and future runs. [Preview Abstract] |
Saturday, April 16, 2005 12:33PM - 1:09PM |
B4.00004: Search for Pentaquarks at CLAS in Photoproduction from Protons Invited Speaker: The CLAS Collaboration at Jefferson Lab has a comprehensive program to search for evidence of a pentaquark in photoproduction from protons and deuterons. Preliminary results from the first of this new round of experiments from a proton target are presented here. The experiment was run in May-July 2004, with a photon energy range from 1.5 to 3.8 GeV. It collected an integrated luminosity of about 70 pb$^{-1}$, which yielded more than an order of magnitude greater statistical precision than previously obtained. We report on the search for the possible reaction $\gamma p \rightarrow \bar{K}^{0} \Theta^{+}$, with $\Theta^{+} \rightarrow K^{+}n$. The $\bar{K}^{0}$ was reconstructed from the invariant mass of its detected $\pi^{+}$ and $\pi^{-}$ decay products, the $K^{+}$ was detected directly, and the undetected neutron $(n)$ was reconstructed from the missing 4-momenta of the detected particles. Preliminary results will be presented and compared with previously published data [1] in the same kinematic region. A second experiment on the proton focusing on higher energies (up to 6 GeV) is scheduled for next year. With ten times more statistics it will test our previously published [2] data on the proton for the possible existence of a pentaquark state in the reaction $\gamma p \rightarrow \pi^{+}K^{-}\Theta^{+}$. \newline \newline References \newline [1] J. Barth \textit{et al.}, Phys. Lett. B \textbf{572}, 127 (2003)\newline [2] V. Kubarovsky \textit{et al.}, Phys. Rev. Lett, \textbf{92}, 032001 (2004) [Preview Abstract] |
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