In an exclusive measurement of the reaction γd→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/c2 with a measured width of 0.021 GeV/c2 FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is (5.2±0.6)σ. The mass and width of the observed peak are consistent with recent reports of a narrow S=+1 baryon by other experimental groups.
Physical Review Letters
Stepanyan, S.; Biselli, Angela; and CLAS Collaboration, "Observation of an exotic S = +1 baryon in
exclusive photoproduction from the deuteron" (2003). Physics Faculty Publications. 94.
S. Stepanyan et al. [CLAS Collaboration], "Observation of an exotic S = +1 baryon in exclusive photoproduction from the deuteron", Phys. Rev. Lett. 91, 252001 (2003) DOI: 10.1103/PhysRevLett.91.252001