Evidence for an Exotic Baryon State, Θ~+(1540), in Photoproduction Reactions from Protons and Deuterons with CLAS

摘要

CLAS photoproduction data on deuterium and hydrogen targets have been analyzed in a search for an exotic baryon state with strangeness S = +1, the Θ~+ (originally named the Z~+). This resonance was predicted recently in theoretical work based on the chiral soliton model as a lowest mass member of an anti-decuplet of 5-quark states. The reaction γd → pK~-K~+n, which requires a final state interaction inside the deuteron, was used in the analysis of deuteron data. In the analysis of proton data, the reaction γd → pK~-K~+n was studied. Evidence for the Θ~+ state is found in both analyzes in the invariant mass distribution of the nK~+. Our results are consistent with previously reported results by LEPS/Spring-8 collaboration (Japan), and by the ITEP (Moscow) group.