Pentaquark Search at HERMES

TL;DR

This paper reports evidence for a narrow pentaquark baryon state at 1528 MeV observed in photoproduction experiments, with a significance of 4 sigma, potentially confirming the existence of the exotic Theta+ pentaquark.

Contribution

First experimental evidence of a narrow pentaquark state at 1528 MeV in photoproduction on a deuterium target, supporting the existence of the Theta+ baryon.

Findings

Evidence for a 1528 MeV baryon state with 4 sigma significance.

Measured intrinsic width of approximately 17 MeV.

Potential identification as the exotic Theta+ pentaquark.

Abstract

Evidence for a narrow baryon state at 1528 +- 2.6(stat) +- 2.1(syst) MeV is presented in quasi-real photoproduction on a deuterium target through the decay channel p,K0 to p,pi+,pi-. The statistical significance of the peak in the p,K0 invariant mass spectrum is 4 standard deviations and its extracted intrinsic width Gamma = 17 +- 9(stat) +- 3(syst) MeV. This state may be interpreted as the predicted S=+1 exotic Theta+ (uudd\bar{s}) pentaquark baryon.