Eur. Phys. J. C (2007) 50: 535-538
https://doi.org/10.1140/epjc/s10052-007-0284-9

Regular Article - Experimental Physics

Observation of a resonance in the K_Sp decay channel at a mass of 1765 MeV/c²

¹ Moscow Lebedev Physics Institute, 117924, Moscow, Russia
² Dipartimento di Fisica and I.N.F.N, Sezione di Genova, 16146, Genova, Italy
³ Max-Planck-Institut für Kernphysik Heidelberg, 69029, Heidelberg, Germany
⁴ Institut des Sciences Nucléaires, Université de Grenoble, 38026, Grenoble Cedex, France
⁵ CERN, 1211, Genève 23, Switzerland
⁶ Physikalisches Institut, Universität Heidelberg, 69120, Heidelberg, Germany
⁷ Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 45, 55099, Mainz, Germany
⁸ University of Bristol, Bristol, BS8 1TL, UK
⁹ TRIUMF, Vancouver, B.C., V6T 2A3, Canada
¹⁰ Thomas Jefferson Lab, Newport News, VA, 23606, USA
¹¹ Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi, 78240, Mexico
¹² Fraunhofer Institut für Solare Energiesysteme, 79100, Freiburg, Germany
¹³ Physik Department E18, Technische Universität München, 85747, Garching, Germany
¹⁴ Fakultät für Physik, Universität Freiburg, Freiburg, Germany
¹⁵ Department of Physics, University of Utah, Salt Lake City, Utah, USA
¹⁶ Gesellschaft für Schwerionenforschung, 64291, Darmstadt, Germany
¹⁷ University of Iowa, Iowa City, Iowa, 52242, USA
¹⁸ Department of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
¹⁹ NIKHEF, 1009 D8, Amsterdam, The Netherlands

^* e-mail: pochodza@kph.uni-mainz.de

Received: 13 December 2006
Revised: 5 March 2007
Published online: 27 March 2007

Abstract

We report on the observation of a K_Sp resonance signal at a mass of 1765 ± 5 MeV/c ², with intrinsic width Γ = 108 ± 22 MeV/c ², produced inclusively in Σ^--nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region x_F>0.7, in this region its production cross section rises approximately linearly with (1-x_F), reaching BR(X→K_Sp)dσ/dx_F=(5.2±2.3)μb per nucleon at x_F=0.8. The hard x_F spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ^*+ state. No corresponding peaks were observed in the K^-p and Λπ^± mass spectra.