Zychor I, Koptev V, Büscher M, Dzyuba A, Keshelashvili I, Kleber V, Koch HR, Krewald S, Maeda Y, Mikirtichyants S, Nekipelov M, Ströher H, Wilkin C. Evidence for an excited hyperon state in pp --> pK+Y0*.
Phys Rev Lett 2006;
96:012002. [PMID:
16486441 DOI:
10.1103/physrevlett.96.012002]
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Abstract
Indications for the production of a neutral excited hyperon in the reaction pp --> pK+Y0* are observed in an experiment performed with the ANKE spectrometer at COSY-Jülich at p(beam) = 3.65 GeV/c. Two final states were investigated simultaneously, viz. Y0* --> pi+X- and pi-X+, and consistent results were obtained in spite of the quite different experimental conditions. The parameters of the hyperon state are M(Y0*) = (1480 +/-15) MeV/c2 and gamma(Y0*) = (60 +/- 15) MeV/c2. The production cross section for Y0* decaying through these channels is of the order of few hundred nanobarns. Since the isospin of the Y0* has not been determined here, it could either be an observation of the sigma(1480), a one-star resonance of the Particle Data Group tables, or, alternatively, a lambda hyperon. Relativistic quark models for the baryon spectrum do not predict any excited hyperon in this mass range and so the Y0* may be of exotic nature.
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