Search for the Theta(+)(1530) pentaquark in antiproton He-4 annihilation at rest

摘要

A research has been made to look for a signature of the positive-strangeness baryon resonance Theta(+) (1530), which is expected to decay into pK(0). A peak is bbserved in the p pi+pi(-) invariant mass distribution in antiproton-He-4 annihilation reactions at rest with production of two pi+pi(-) pairs with invariant mass close to the KO mass. The annihilation reactions on 4 He can involve two to four nucleons producing an energy blob characterized by high strangeness content. The peak is centred around 1560.0 +/- 3.7 MeV and its width is very narrow. The statistical significance is 2.7; this value is considered of not sufficient significance to claim support of the Theta(+). The data were collected with the Obelix spectrometer at the LEAR machine of CERN. (c) 2006 Published by Elsevier B.V.