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The J-PARC Hadron Facility is designed as a multipurpose experimental facility for a wide range of particle and nuclear physics programs, aiming to provide the world highest intensity secondary beams. The first primary beam has been successfully extracted and transported to the beam dump on January 2009. Currently three secondary beam lines come into operation, and the new beam line will be completed in the early summer of 2010. Various experimental programs are proposed at each beamline and some of them are preparing to start physics run. Most of the experimental researches concerns the studies of hypernuclei and searches for new hadronic states. As the first experiment at the J-PARC Hadron Facility, search for the Θ+ pentaquark via pion-induced hadronic reaction will be performed in the autumn of 2010. The current status and recent results of the commissioning for the beam line are reported.
The J-PARC Hadron Facility is designed as a multipurpose experimental facility for a wide range of particle and nuclear physics programs, aiming to provide the world highest intensity secondary beams. The first primary beam has been successfully extracted and transported to the beam dump on January 2009. Currently three secondary beam lines come into operation, and the new beam line will be completed in the early summer of 2010. Various experimental programs are proposed at each beamline and some of them are preparing to start physics run. Most of the experimental researches concerns the studies of hypernuclei and searches for new hadronic states. As the first experiment at the J-PARC Hadron Facility, search for the Θ+ pentaquark via pion-induced hadronic reaction will be performed in the autumn of 2010. The current status and recent results of the commissioning for the beam line are reported.
Using the QCD sum rule method, various pentaquark states with strangeness S = +1 are investigated. In order to find a region in the Borel mass, where the the operator product expansion (OPE) is thought to converge and the sum rule is dominated by the resonance pole, we calculate the OPE up to dimension 14 and employ the difference of two independent correlators to construct the sum rules, by which the constributions of the higher-energy continuum states are strongly suppressed. As a result of this investigation, we find stable Borel mass curves for the quantum numbers IJ π = 0 1 2 − , 1 1 2 − , 0 3 2 + , 1 3 2 + , suggesting the existence of resonance poles in these channels. As the width of the J π = 1 2 − states is likely to be very broad, and Θ + (1540) is thought to be an isosinglet state, we conclude that the most probable candidate for Θ + (1540) is the state with quantum numbers IJ π = 0 3 2 + .
Motivated by the recent experimental discoveries of multi-quark candidates, e.g., the $\Theta^+(1540)$, we study multi-quark systems in lattice QCD. First, we perform accurate mass measurements of low-lying 5Q states with $J=1/2$ and I=0 in both positive- and negative-parity channels in anisotropic lattice QCD. The lowest positive-parity 5Q state is found to have a large mass of about 2.24GeV after the chiral extrapolation. To single out the compact 5Q state from $NK$ scattering states, we develop a new method with the hybrid-boundary condition (HBC), and find no evidence of the compact 5Q state below 1.75GeV in the negative-parity channel. Second, we perform the first study of the multi-quark potential in lattice QCD to clarify the inter-quark interaction in multi-quark systems. The 5Q potential $V_{\rm 5Q}$ for the QQ-${\rm \bar{Q}}$-QQ system is found to be well described by the ``OGE Coulomb plus multi-Y Ansatz": the sum of the one-gluon-exchange (OGE) Coulomb term and the multi-Y-type linear term based on the flux-tube picture. The 4Q potential $V_{\rm 4Q}$ for the QQ-${\rm \bar{Q}\bar{Q}}$ system is also described by the OGE Coulomb plus multi-Y Ansatz, when QQ and $\rm \bar Q \bar Q$ are well separated. The 4Q system is described as a "two-meson" state with disconnected flux tubes, when the nearest quark and antiquark pair is spatially close. We observe a lattice-QCD evidence for the ``flip-flop'', i.e., the flux-tube recombination between the connected 4Q state and the ``two-meson'' state. On the confinement mechanism, the lattice QCD results indicate the flux-tube-type linear confinement in multi-quark hadrons.Comment: 22 pages, 3 tables, 16 figures. Talk given at International Workshop on Quark Nuclear Physics 2005 (QNP05), Phoenix Park, Korea, 22-24, Feb., 200
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