Search for the $\Theta^+$ in Photoproduction on the Deuteron

TL;DR

This study conducted a high-statistics photoproduction experiment on deuterium to search for the $ heta^+$ pentaquark, but found no significant evidence of its existence within the examined mass range.

Contribution

The paper provides the first high-statistics search for the $ heta^+$ in photoproduction on deuterium, setting upper limits on its production cross section.

Findings

No significant narrow peak observed in the 1.5-1.6 GeV mass region.

Upper limit on $ heta^+$ production cross section estimated at 4-5 nb.

Methodology includes using missing mass technique and model-dependent rescattering corrections.

Abstract

A high-statistics experiment on a deuterium target was performed using a real photon beam with energies up to 3.6 GeV at the CLAS detector of Jefferson Lab. The reaction reported here is for $\gamma d \to p K^- K^+ n$ where the neutron was identified using the missing mass technique. No statistically significant narrow peak in the mass region from 1.5-1.6 GeV was found. An upper limit on the elementary process $\gamma n \to K^- \Theta^+$ was estimated to be about 4-5 nb, using a model-dependent correction for rescattering determined from $\Lambda$(1520) production. Other reactions with less model-dependence are being pursued.