A Search for Sigma^0_5, N^0_5 and Theta^++ Pentaquark States

TL;DR

This study conducted a high-resolution search for narrow pentaquark states near 1500-1850 MeV in electroproduction experiments but found no significant signals, setting upper limits on their production rates.

Contribution

It provides the first high-resolution search for specific pentaquark states and establishes upper limits on their production cross sections in electroproduction.

Findings

No statistically significant pentaquark signals observed.

Upper limits on production are between 0.7% and 4.2% of Lambda(1520) production.

Search constrains the existence of these pentaquark states.

Abstract

A high-resolution (sigma_instr. = 1.5 MeV) search for narrow states (Gamma < 10 MeV) with masses of M_x approx 1500-1850 MeV in ep -> e'K^+ X, e'K^- X and e' pi^+ X electroproduction at small angles and low Q^2 was performed. These states would be candidate partner states of the reported Theta^+(1540) pentaquark. No statistically significant signal was observed in any of the channels at 90% C.L. Upper limits on forward production were determined to be between 0.7% and 4.2% of the Lambda(1520) production cross section, depending on the channel and the assumed mass and width of the state.