Search for Θ+ and Ξ−−3/2 pentaquarks in HERA-B

Abstract

A search for Θ+(1540) and Ξ−−3/2(1860) pentaquark candidates has been performed in proton-induced reactions on C, Ti and W targets at studying the pK0S respectively Ξ−π− and Ξ−π+ (and charge conjugated (c.c.)) decay channels at mid-rapidity. With sensitivities of Br × dσ/dxF < 5 to 25 μb/nucleon, we find no evidence for narrow pentaquark peaks in any of the studied final states. Preliminary values for the upper limit of relative yield ratios at mid-rapidity are Θ+(1540)/Λ(1520) < 0.02, Br × Ξ−−3/2(1862)/Ξ(1530)0 < 0.077 and at 95 % CL.