Evidence for an Excited Hyperon State in pppK+Y0*

I. Zychor, V. Koptev, M. Büscher, A. Dzyuba, I. Keshelashvili, V. Kleber, H. R. Koch, S. Krewald, Y. Maeda, S. Mikirtichyants, M. Nekipelov, H. Ströher, and C. Wilkin
Phys. Rev. Lett. 96, 012002 – Published 9 January 2006

Abstract

Indications for the production of a neutral excited hyperon in the reaction pppK+Y0* are observed in an experiment performed with the ANKE spectrometer at COSY-Jülich at pbeam=3.65GeV/c. Two final states were investigated simultaneously, viz. Y0*π+X and πX+, 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 Γ(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 Σ(1480), a one-star resonance of the Particle Data Group tables, or, alternatively, a Λ 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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  • Received 10 June 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.012002

©2006 American Physical Society

Authors & Affiliations

I. Zychor1, V. Koptev2, M. Büscher3, A. Dzyuba2, I. Keshelashvili3,4, V. Kleber5,*, H. R. Koch3, S. Krewald3, Y. Maeda3, S. Mikirtichyants2, M. Nekipelov2,3, H. Ströher3, and C. Wilkin6

  • 1The Andrzej Sołtan Institute for Nuclear Studies, 05400 Świerk, Poland
  • 2High Energy Physics Department, Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia
  • 3Institut für Kernphysik, Forschungszentrum Jülich, 52425 Jülich, Germany
  • 4High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia
  • 5Institut für Kernphysik, Universität zu Köln, 550937 Köln, Germany
  • 6University College London, London WC1E 6BT, United Kingdom

  • *Present address: Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany.

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Vol. 96, Iss. 1 — 13 January 2006

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