FIZIKA B 13 (2004)  2, 605-608

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for the LEPS collaboration

Research Center for Nuclear Physics, Osaka University, 10-1 Mihogaoka, Ibaraki,
Osaka, 567-0047 Japan

Received 27 October 2003;        Accepted 24 May 2004
Online 22 November 2004

A highly-polarized photon beam produced via the backward Compton scattering of polarized laser photons off the high-energy electrons is utilized for nuclear and particle physics experiments at SPring-8. The present status of the experiments at the Laser Electron Photon beamline at SPring-8 (LEPS) is reported. From the recent results, the evidence for a five-quark baryon resonance is presented. A sharp baryon resonance peak was observed at 1.540.01 GeV/c2 with a width smaller than 25 MeV/c2 in the gn K+K-n reaction on 12C. The resonance has the strangeness quantum number S=+1 and it can not be formed by three quarks.

PACS numbers: 25.20.-x,14.20.Gk,14.80.-j
UDC 539.12

Keywords: backward Compton scattering of polarized laser photons off high-energy electrons, five-quark baryon resonance

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