Abstract

SPring-8/LEPS is a highly polarized GeV photon beam facility for hadron physics. Photoproduction of hadrons with the strangeness have been studied intensively. In this article, recent results of LEPS and status of the development of LEPS2 project are reported. The spin-density matrix elements of K ⁎ 0 photoproduction associated with a Σ + have been measured for the first time in the forward angle region at LEPS. The result show the contribution of natural parity exchange in t -channel, which is consistent with a κ (800) meson-exchange model. On the pentaquark candidate, Θ + , a clear peak structure is seen in new exclusive analyses using increased statistics data of the γ d → K + K − X reaction. In order to increase the luminosity and to extend the detector acceptance, a new project, LEPS II, has started. The status of the construction of the LEPS II is described in this article.

Highlights

  • In the quark model, scalar mesons are described as the L = 1 excitation of qqpair

  • If the signal of Θ+ is confirmed by LEPS in new data with higher statistics, in order to explain the null result of CLAS, it is indispensable to measure the production cross section in wide angle region

  • The LEPS II detector will be installed in the solenoid magnet, which consists of double-sided silicon strip detectors (DSSD), forward drift chambers (FDC), a time projection chamber (TPC), time of propagation counter (TOP), resistive plate chamber (RPC-TOF), barrel electromagnetic calorimeter (EMCAL), and aerogel Cerenkov counter (AC)

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Summary

Introduction

We report on the measurement of linear polarization observables of K∗0Σ+ photoproduction off proton at LEPS [4] These observables, the spin-density matrix elements, are sensitive to meson exchange in t-channel reaction. By comparing the experimental data measured with two theoretical calculation, one with minimal κ meson exchange and the other with substantial exchange, we can investigate the existence of the κ(800). The observed asymmetry favors the model II with the contribution of κ

LEPS II experiment
LEPS II beam line
LEPS II detector
Findings
Summary
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