Evidence for a narrow |S |= 1 baryon state at a mass of 1528 MeV in quasi-real photoproduction

By H. C. A. Airapetian, et al. 2003

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Abstract Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0S→pπ+π−. A peak is observed in the pK0S  invariant mass spectrum at 1528±2.6(stat)±2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental resolution of σ=4.3–6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Θ + (uudd s ) pentaquark baryon. No signal for an hypothetical Θ++ baryon was observed in the pK+ invariant mass distribution. The absence of such a signal indicates that an isotensor Θ is excluded and an isovector Θ is unlikely.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/d910a328f6158a159408d28cf2097af2fa22b5c6