Search for Theta^+ and Xi^{--}_{3/2} pentaquarks in HERA-B

TL;DR

This study searched for pentaquark particles Theta^+ and Xi^{--}_{3/2} in high-energy proton collisions but found no evidence, setting upper limits on their production relative to known particles.

Contribution

First experimental search for these pentaquarks at HERA-B with specific decay channels and setting upper limits on their production rates.

Findings

No evidence for narrow pentaquark peaks in studied channels.

Upper limits on production ratios relative to known particles.

Sensitivity of the search ranged from 5 to 25 microbarn/nucleon.

Abstract

A search for Theta^+(1540) and Xi^{--}_{3/2}(1862) pentaquark candidates has been performed in proton-induced reactions on C, Ti and W targets at sqrt(s) = 41.6 GeV studying the pK_s resp. Xi^-pi^- and Xi^-pi^+ (and charge conjugated) decay channels at mid-rapidity. With sensitivities of (Br)x(dsigma/dx_F) < 5 to 25 microbarn/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 (Theta^+(1540)) / (Lambda(1520)) < 0.02, (Br)x(Xi^{--}_{3/2}(1862)) / (Xi(1530)^0) < 0.077, and (Br)x(Xi_bar^{++}_{3/2}(1862)) / (Xi_bar(1530)^0) < 0.058 at 95% CL.