Observation of an exotic S = +1 baryon in exclusive photoproduction from the deuteron.
In an exclusive measurement of the reaction gammad-->K(+)K(-)pn, a narrow peak that can be attributed to an exotic baryon with strangeness S=+1 is seen in the K(+)n invariant mass spectrum. The peak is at 1.542+/-0.005 GeV/c(2) with a measured width of 0.021 GeV/c(2) FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is (5.2+/-0.6)sigma. The mass and width of the observed peak are consistent with recent reports of a narrow S=+1 baryon by other experimental groups.
Stepanyan
S
S
Thomas Jefferson National Accelerator Laboratory, Newport News, Virginia 23606, USA and Old Dominion University, Norfolk, Virginia 23529, USA.
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Bradford
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