Evidence for the positive-strangeness pentaquark Theta(+) in photoproduction with the SAPHIR detector at ELSA

摘要

The positive-strangeness baryon resonance (Theta(+) is observed in photoproduction of the nK+K-S(0) final state with the SAPHIR detector at the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in the nK(+) invariant mass distribution with a 4.8sigma confidence level. We find a mass MTheta+ = 1540 +/- 4 +/- 2 MeV and an upper limit of the width Gamma(Theta+) pK(+)K(-) at the expected strength we conclude that the Theta(+) must be isoscalar. (C) 2003 Published by Elsevier B.V. References: 30