Showing papers by "Noriyoshi Ishii published in 2015"

Coupled-channel approach to strangeness S =− 2 baryon-bayron interactions in lattice QCD

Abstract: Coupled-channel approach to strangeness S = −2 baryon–bayron interactions in lattice QCD Kenji Sasaki1,∗, Sinya Aoki1,2, Takumi Doi3, Tetsuo Hatsuda3, Yoichi Ikeda3, Takashi Inoue4, Noriyoshi Ishii5, and Keiko Murano5 (on behalf of the HAL QCD Collaboration) 1Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan 2Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan 3Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198, Japan 4Nihon University, College of Bioresource Sciences, Fujisawa 252-0880, Japan 5Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki, Osaka 567-0047, Japan ∗E-mail: kenjis@het.ph.tsukuba.ac.jp

Medium-heavy nuclei from nucleon-nucleon interactions in lattice QCD

Abstract: On the basis of the Brueckner-Hartree-Fock method with the nucleon-nucleon forces obtained from lattice QCD simulations, the properties of the medium-heavy doubly-magic nuclei such as 16^O and 40^Ca are investigated. We found that those nuclei are bound for the pseudo-scalar meson mass M_PS ~ 470 MeV. The mass number dependence of the binding energies, single-particle spectra and density distributions are qualitatively consistent with those expected from empirical data at the physical point, although these hypothetical nuclei at heavy quark mass have smaller binding energies than the real nuclei.

Omega-Omega interaction from 2+1-flavor lattice quantum chromodynamics

Abstract: We investigate the interaction between $\Omega$ baryons in the ${^{1\!}S}_0$ channel from $2{+ }1$-flavor lattice quantum chromodynamics (QCD) simulations. On the basis of the HAL QCD method, the $\Omega \Omega$ potential is extracted from the Nambu–Bethe–Salpeter wave function calculated on the lattice by using the PACS-CS gauge configurations with a lattice spacing of $a\simeq 0.09$fm, a lattice volume of $L\simeq 2.9$fm, and quark masses corresponding to $m_\pi \simeq 700$MeV and $m_\Omega \simeq 1970$MeV. The $\Omega \Omega$ potential has a repulsive core at short distances and an attractive well at intermediate distances. Accordingly, the phase shift obtained from the potential shows moderate attraction at low energies. Our data indicate that the $\Omega \Omega$ system with the present quark masses may appear close to the unitary limit where the scattering length diverges.

Sharing lattice QCD data over a widely distributed file system

Abstract: JLDG is a data-grid for the lattice QCD (LQCD) community in Japan Several large research groups in Japan have been working on lattice QCD simulations using supercomputers distributed over distant sites The JLDG provides such collaborations with an efficient method of data management and sharingFile servers installed on 9 sites are connected to the NII SINET VPN and are bound into a single file system with the GFarm The file system looks the same from any sites, so that users can do analyses on a supercomputer on a site, using data generated and stored in the JLDG at a different siteWe present a brief description of hardware and software of the JLDG, including a recently developed subsystem for cooperating with the HPCI shared storage, and report performance and statistics of the JLDG As of April 2015, 15 research groups (61 users) store their daily research data of 47PB including replica and 68 million files in total Number of publications for works which used the JLDG is 98 The large number of publications and recent rapid increase of disk usage convince us that the JLDG has grown up into a useful infrastructure for LQCD community in Japan

$\Omega\Omega$ interaction from 2+1 flavor lattice QCD

Abstract: We investigate the interaction between $\Omega$ baryons in the $^1S_0$ channel from 2+1 flavor lattice QCD simulations. On the basis of the HAL QCD method, the $\Omega\Omega$ potential is extracted from the Nambu-Bethe-Salpeter wave function calculated on the lattice by using the PACS-CS gauge configurations with the lattice spacing $a\simeq 0.09$ fm, the lattice volume $L\simeq 2.9$ fm and the quark masses corresponding to $m_\pi \simeq 700$ MeV and $m_\Omega \simeq 1970$ MeV. The $\Omega\Omega$ potential has a repulsive core at short distance and an attractive well at intermediate distance. Accordingly, the phase shift obtained from the potential shows moderate attraction at low energies. Our data indicate that the $\Omega\Omega$ system with the present quark masses may appear close to the unitary limit where the scattering length diverges.

Coupled channel approach to strangeness S = -2 baryon-bayron interactions in Lattice QCD

Abstract: The baryon-baryon interactions with strangeness S = -2 with the flavor SU(3) breaking are calculated for the first time by using the HAL QCD method extended to coupled channel system in lattice QCD. The potential matrices are extracted from the Nambu-Bethe-Salpeter wave functions obtained by the 2+1 flavor gauge configurations of CP-PACS/JLQCD Collaborations with a physical volume of 1.93 fm cubed and with m_pi/m_K = 0.96, 0.90, 0.86. The spatial structure and the quark mass dependence of the potential matrix in the baryon basis and in the SU(3) basis are investigated.

First results of baryon interactions from lattice QCD with physical masses (1) -- General overview and two-nucleon forces --

Abstract: We present the lattice QCD studies for baryon-baryon interactions for the first time with (almost) physical quark masses. $N_f = 2+1$ gauge configurations are generated with the Iwasaki gauge action and nonperturbatively $O(a)$-improved Wilson quark action with stout smearing on the lattice of $(96 a)^4 \simeq (8.2 {\rm fm})^4$ with $a \simeq 0.085$ fm, where $m_\pi \simeq 146$ MeV and $m_K \simeq 525$ MeV. Baryon forces are calculated from Nambu-Bethe-Salpeter (NBS) correlation functions using the time-dependent HAL QCD method. In this report, we first give the general overview of the theoretical frameworks essential to the physical point calculation of baryon forces. We then present the numerical results for the two-nucleon central and tensor forces in $^3S_1$-$^3D_1$ coupled channel and the central force in $^1S_0$ channel. In particular, a clear signal is obtained for the tensor force.

Towards Lattice QCD Baryon Forces at the Physical Point: First Results

Abstract: Lattice QCD calculations of baryon forces are performed for the first time with (almost) physical quark masses. $N_f = 2+1$ dynamical clover fermion gauge configurations are generated at the lattice spacing of $a \simeq 0.085$ fm on a $(96 a)^4 \simeq (8.2 {\rm fm})^4$ lattice with quark masses corresponding to $(m_\pi, m_K) \simeq (146, 525)$ MeV. Baryon forces are calculated using the time-dependent HAL QCD method. In this report, we study $\Xi\Xi$ and $NN$ systems both in $^1S_0$ and $^3S_1$-$^3D_1$ channels, and the results for the central and tensor forces as well as phase shifts in the $\Xi\Xi$ $(^1S_0)$ channel are presented.