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FIZIKA B 13 (2004) 2, 605-608
 
EXPERIMENTAL PROGRAM AT SPring-8
TOMOAKI HOTTA
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 1.54±0.01 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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