Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session DA: Strangeness Aspects of Nuclear Physics |
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Chair: Hirokazu Tamura, Tohoku University Room: Kohala 1 |
Thursday, October 9, 2014 9:00AM - 9:45AM |
DA.00001: Strangeness Physics on the Lattice Invited Speaker: Martin Savage Through advances in high performance computing and associated algorithms, it is finally becoming possible to determine basic properties of simple hadronic systems at the physical quark masses, including QED, directly from the underlying theory of the strong interactions with the numerical technique of Lattice QCD. After reviewing this recent progress, my presentation will focus on the developments in Lattice QCD calculations of quantities of importance to nuclear physics where strange quarks play a key role, e.g. the interactions between hyperons and nucleons, the binding energies of light hypernuclei and matrix elements of strange-quark operators in the nucleon. [Preview Abstract] |
Thursday, October 9, 2014 9:45AM - 10:30AM |
DA.00002: Electromagnetic Strangeness Production at GeV Energies Invited Speaker: Reinhard Schumacher An overview of a decade of elementary strangeness production results from various labs will be discussed, with emphasis on CLAS at Jefferson Lab. Kaon photoproduction off the nucleon of the ground state $\Lambda$ and $\Sigma^0$ states has been instrumental in identifying the $N^*$ resonance structure of the nucleon around 2 GeV. Spin observables, aiming at ``complete'' determination of the photoproduction amplitudes, promise to further constrain the excitation spectrum of nucleons. Electroproduction measurements have extended structure function information to non-zero $Q^2$. Photoproduction of the excited hyperons, the $\Sigma^{0}(1385)$, $\Lambda(1405)$, and $\Lambda(1520)$ in the reactions $\gamma p\to K^+ Y^{\ast}\to K^+ \Sigma \pi$, can be compared to the hyperon ground state reactions for the first time. These cross sections have been compared to current theoretical models based on the effective Lagrangian approach, with varying success. The cross sections for the $\Lambda(1405)$ region are strikingly different for the $\Sigma^+\pi^-$, $\Sigma^0\pi^0$, and $\Sigma^-\pi^+$ decay channels, indicating the effect of isospin interference, especially at $W$ values close to the threshold. We show how this behavior is reflected in the $\Sigma\pi$ mass distributions of the $\Lambda(1405)$. Chiral unitary models of the $\Lambda(1405)$ and related non-strange baryonic states suggest how the $\Lambda(1405)$ is a structure of several interfering poles, which may explain the peculiar shapes. We highlight also the first measurement of the spin and parity of the $\Lambda(1405)$. Finally, we outline the next experimental steps to be taken in strangeness electromagnetic production in the Jefferson Lab 12 GeV era. [Preview Abstract] |
Thursday, October 9, 2014 10:30AM - 11:15AM |
DA.00003: Spectroscopy of $\Lambda$ hypernuclei using Electron Beams Invited Speaker: Satoshi N. Nakamura Precision spectroscopy of $\Lambda $ hypernuclei is quite important tool to study the baryon-nucleon interaction. After a decade of efforts at JLab, hypernuclear spectroscopy with electron beams was established. Active discussion on the charge symmetry breaking (CSB) of the $\Lambda $N interaction was triggered by a recent measurement of the ground state of $^{7}_{\Lambda}$He at JLab as well as progresses of theoretical works. Latest results of the HKS-HES experiment (JLab E05-115) on $^{7}_{\Lambda}$He, $^{10}_{\Lambda}$Be and $^{12}_{\Lambda}$B will be reviewed from the view point of the $\Lambda $N CSB effects. Since the discussion on the $\Lambda $N CSB effects started from the differences of energy levels of A$=$4 hypernuclear iso-doublet ($^{4}_{\Lambda}$H and $^{4}_{\Lambda}$He), the study of them with state-of-art experimental techniques is important to understand the $\Lambda$N CSB effect. At Mainz, a new research technique, the decay pion spectroscopy of electro-produced hypernuclei, has been developed to study absolute binding energies of light hypernuclei. Latest status of the $^{4}_{\Lambda}$H study at Mainz will be reported. As well as spectroscopy of light hypernuclei, precise measurements of single particle energies for heavier hypernuclei are quite important to study the baryon interaction. Future prospects on study of heavier hypernuclei at JLab will be discussed. [Preview Abstract] |
Thursday, October 9, 2014 11:15AM - 12:00PM |
DA.00004: Structure of few-body hypernuclei Invited Speaker: Emiko Hiyama Recently, in hypernuclear physics, we had three neutron-rich $\Lambda$ hypernuclei, $nn \Lambda$, $^6_{\Lambda}$H and $^7_{\Lambda}$He. These observation are very important by following reason: One of the research goal in hypernuclear physics is to study new dynamical features by injecting a $\Lambda$ particle into a nucleus. Since there is no Pauli principle between nucleons and a $\Lambda$ particle, the $\Lambda$ participation gives rise to more bound states and significant contraction of nuclear cores, especially in light systems. If a $\Lambda$ particle is added to neutron-rich nuclei to have a weakly bound state or resonant one, a resultant hypernucleus will become more stable against neutron decay. Three observed hypernuclei are such systems. Currently, it is important to investigate structure of these $\Lambda$ hypernuclei theoretically. For this purpose, I will report these hypernuclei within the framework of $nn\Lambda$, $tnn\Lambda$ and $\alpha \Lambda NN$ three- and four-body model. The following will be reported: (1) To study $nn\Lambda$ system, the coupled channel calculation of $NN\Lambda$ and $NN\Sigma$ is performed. We do not find any $nn\Lambda$ bound state, which is inconsistent with the interpretation of the data. (2) Interactions among the constituent subunits in $^6_{\Lambda}$H are determined so as to reproduce reasonably well the observed low energy properties of the $tn$, $t\Lambda$ and $tnn$. As long as we reproduce the energy and width of $^5$H within the error bar, the ground state of $^6_{\Lambda}$H is obtained as a resonant state. (3) In our previous work, we predicted the ground state, $1/2^+$ and the excited states, $3/2^+_1$ and $5/2^+$. And the recent observed data at Jlab are in good agreement with our prediction. Here, I will report another new states, $3/2_2$ and $5/2^+_2$ in $^7_{\Lambda}$He which is second $2^+$ state of $^6$He coupled to $0s$-orbit of $\Lambda$ particle. And I will report the structure of these spectra. [Preview Abstract] |
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