Evidence for a narrow | S | = 1 baryon state at a mass of 1528 MeV in quasi - real photoproduction HERMES
نویسندگان
چکیده
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0 S → pπ+π−. A peak is observed in the pK0 S 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+(uudds̄) 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. 2004 Elsevier B.V. All rights reserved. PACS: 12.39.Mk; 13.60.-r; 13.60.Rj; 14.20.-c HERMES Collaboration / Physics Letters B 585 (2004) 213–222 215
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تاریخ انتشار 2004