Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session CJ: Mini-Symposium on Progress in Strangeness Physics II |
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Chair: Toshio Motoba, Osaka Electro-Communication University Room: Queens 4 |
Thursday, October 15, 2009 9:00AM - 9:30AM |
CJ.00001: Baryon Resonances from Measurements of Strange Baryon Production Invited Speaker: The spectrum of excited states of the nucleon has been a topic of interest for both experimental and theoretical investigations for many years. The goal is to measure the masses of resonances of the nucleons (N*), of the hyperons (Y*) and of other baryons such as the Cascade. Once these masses are known, then theoretical calculations (either models or lattice gauge theory) can be used to interpret the resonance spectrum, hence making a connection with the underlying framework of QCD. Put simply, the confinement of quarks in baryons is not yet completely understood. In this talk, the spectrum of baryon resonances will be reviewed and evidence for new baryon resonances coming from measurements of strange baryon production will be discussed. Many of the new resonances come from comparisons of photo- and electro-production data with theoretical models. Even with these new resonances, many of the resonances predicted by the constituent quark model are not found. This suggests that lattice gauge calculations may be necessary to interpret the spectrum of baryon resonances, as some theorists have speculated for many years. Nonetheless, future experimental work is needed to clarify the situation. Some suggestions for future directions will be presented. [Preview Abstract] |
Thursday, October 15, 2009 9:30AM - 9:45AM |
CJ.00002: Measurement of $\gamma d \rightarrow K^0 \Lambda p$ reaction with NKS2 at SENDAI Kenta Futatsukawa Kaon photoproduction plays an important role in the investigation of meson-baryon interactions, the structures of hadrons, and in search for missing resonances. Among kaon photoproduction processes, the $\gamma n \rightarrow K^0 \Lambda$ reaction is a unique process and is vital to understanding kaon photoproduction. In order to study this reaction, we have constructed the new spectrometer (NKS2) optimized to cover the forward region, thus making it possible to measure much larger kinematical region of $K^0$. We have performed the experiment of $K^0$ photoproduction near the threshold region ($E_{\gamma}$=0.8$-$1.1~GeV) with a liquid deuterium target at the Laboratory of Nuclear Science, Tohoku University(LNS-Tohoku). The data analysis is in progress. The preliminary results of the cross section will be presented in this talk. [Preview Abstract] |
Thursday, October 15, 2009 9:45AM - 10:00AM |
CJ.00003: The investigation of strangeness photoproduction in the threshold region at LNS-Tohoku Masashi Kaneta Strangeness photoproduction near the threshold is important to study the production mechanism. The process had been intensively studied based on the high-quality data of the charged kaon channel, $\gamma +p \quad \to \quad K^{ + }$+ $\Lambda (\Sigma ^{0})$. However, there was no reliable data for the neutral kaon channel $\gamma +n \quad \to \quad K^{ 0}_{ }+\Lambda $ and the theoretical investigations suffered seriously from the lack of the data. In order to obtain reliable data for the neutral kaon photoproduction process, we have been making an effort to measure the $\gamma +n \quad \to \quad K^{ 0}$+ $\Lambda $ reaction in the $\pi ^{+} \quad \pi ^{-}$ decay channel of $K^{ 0}_{S}$, using a liquid deuterium target and a tagged photon beam in the energy region from 0.8 to 1.1 GeV at Laboratory of Nuclear Science (LNS), Tohoku University. We have taken exploratory data quite successfully with use of Neutral Kaon Spectrometer (NKS). Now we are at the second stage of the experimental study using a new spectrometer for extending the previous experiment in the statistics and the momentum/angular acceptance for $K^{ 0}s$ and $\Lambda $. The data was taken in 2005-2007. In this talk, we will present recent results from the NKS2 experiment and future plan of the experiment. [Preview Abstract] |
Thursday, October 15, 2009 10:00AM - 10:15AM |
CJ.00004: Pseudoscalar-meson-octet-baryon coupling constants in two-flavor lattice QCD M. Oka, G. Erkol, T.T. Takahashi We evaluate the $\pi N\!N$, $\pi\Sigma\Sigma$, $\pi\Lambda\Sigma$, $K\Lambda N$ and $K \Sigma N$ coupling constants and the corresponding monopole masses in lattice QCD with two flavors of dynamical quarks. The parameters representing the SU(3)-flavor symmetry are computed at the point where the three quark flavors are degenerate at the physical $s$-quark mass. In particular, we obtain $\alpha\equiv F/(F+D)=0.395(6)$. The quark-mass dependences of the coupling constants are obtained by changing the $u$- and the $d$-quark masses. We find that the SU(3)-flavor parameters have weak quark-mass dependence and thus the SU(3)-flavor symmetry is broken by only a few percent at each quark-mass point we consider. [Preview Abstract] |
Thursday, October 15, 2009 10:15AM - 10:30AM |
CJ.00005: Prospects of realistic Quark-model baryon-baryon interactions Choki Nakamoto, Yoshikazu Fujiwara, Yasuyuki Suzuki The QCD-inspired spin-flavor $SU_6$ quark model for the baryon- baryon interaction, proposed by the Kyoto-Niigata group, is a unified model for the full octet-baryons ($B_8=N$, $\Lambda$, $\Sigma$ and $\Xi$), which has achieved very accurate descriptions of the nucleon-nucleon ($NN$) and hyperon-nucleon ($YN$) interactions. The present model, fss2, is not only more sophisticated than the previous model, FSS, for the description of the realistic $NN$ and $YN$ interaction, but also valid for reproducing of the existing experimental data in the strangeness $S=-2$ sector. We attempt to construct the more realistic quark-model baryon- baryon interactions possessing both the desirable feature of the quark model and the accuracy equivalent with fss2 for the experimental data. [Preview Abstract] |
Thursday, October 15, 2009 10:30AM - 10:45AM |
CJ.00006: A novel spectral broadening from vector-axial-vector mixing in dense matter Masayasu Harada, Chihiro Sasaki The presence of baryonic matter leads to the mixing between transverse $\rho$ and $a_1$ mesons through a set of $\omega\rho a_1$-type interactions, which results in the modification to the dispersion relation. We show that a clear enhancement of the vector spectral function appears below $\sqrt{s}=m_\rho$ for small three-momenta of the $\rho$ meson, and thus the vector spectrum exhibits broadening. We also discuss its relevance to dilepton measurements. [Preview Abstract] |
Thursday, October 15, 2009 10:45AM - 11:00AM |
CJ.00007: Perturbation of Chiral Soliton Anjan Biswas This talk is on perturbation of soliton due to the chiral Nonlinear Schrodinger's equation by the aid of soliton perturbation theory. The perturbation term that is studied is the quantum potential perturbation of the chiral soliton that is known as Bohm potential. The stable fixed point of the chiral soliton parameters is obtained. [Preview Abstract] |
Thursday, October 15, 2009 11:00AM - 11:15AM |
CJ.00008: Experimental Study of $\Lambda$(1405) by a Virtual Meson-Baryon Scattering Hiroyuki Noumi It is a long standing problem if $\Lambda$(1405) is a 3-quark state or a kaon nucleon bound state. Recent theoretical studies based on chiral unitary model claimed that $\Lambda$(1405) may consist of two components in a coupled-channel $\bar{K}N-\pi\Sigma$ system. Namely, poles coupled to $\bar{K} N$ and $\pi\Sigma$ are suggested at different positions. If it is true, decomposition of the two components are desired in the $\Lambda$(1405) spectrum. Since the $\Lambda(1405)$ state sits below $\bar{K}N$ threshold, it is of essentially importance to investigate a $\bar{K}N$ scattering process in a virtual state. The ($K^-$,n) reaction on deuteron is promissing to enhance a virtual $\bar{K}N$ reaction to produce $\Lambda$(1405). The experimetal study of $\Lambda$(1405) via the reaction has been proposed at J-PARC. [Preview Abstract] |
Thursday, October 15, 2009 11:15AM - 11:30AM |
CJ.00009: Application of Likelihood PID Method in Hypernuclear Experiment E01-011 Pavlo Baturin, Joerg Reinhold JLab experiment E01-011, employed the (e,e'K$^+$) reaction for a new generation of hypernuclear spectroscopy studies. A new high resolution kaon spectrometer (HKS) together with the newly introduced tilt method for the electron spectrometer (ENGE) allowed to simultaneously achieve excellent energy resolution and significantly reduce background events due to bremsstrahlung and Moller electrons. The energy spectra of exotic neutron rich $\Lambda$ hypernuclei ($^7_{\Lambda}$He, $^9_{\Lambda}$Li, $^{12}_{\Lambda}$B, $^{28}_{\Lambda}$Al) were measured with high statistics. Efficient kaon particle identification (PID) is key to obtaining good signal to background ratios. We introduced a method based on probability density functions for independent detector distributions that are combined into likelihood values for each possible particle. The goal is to improve statistical significance, especially for low statistic core excited states that are observed in the excitation spectra. The presentation will illustrate the novel likelihood approach, compare it to standard PID cuts, discuss the method's benefits, and show the effect on the missing mass distributions. [Preview Abstract] |
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