Differential cross section and photon beam asymmetry for the gamma n -> K+ Sigma- reaction at Egamma=1.5-2.4 GeV

TL;DR

This study measures differential cross sections and photon beam asymmetries for gamma n -> K+ Sigma- and gamma p -> K+ Sigma0 reactions in the 1.5-2.4 GeV energy range, revealing unexpected asymmetry differences and dominance of K*-exchange.

Contribution

It provides new experimental data on cross sections and asymmetries for these reactions, highlighting discrepancies with simple theoretical models.

Findings

Cross section ratio close to 1 instead of expected 2

Large positive asymmetries for gamma n -> K+ Sigma-

Significant difference in asymmetries between reactions

Abstract

Differential cross sections and photon beam asymmetries have been measured for the gamma n -> K+ Sigma- and gamma p -> K+ Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of Egamma=1.5-2.4 GeV at 0.6<cosTheta<1. The cross section ratio of sigma(K+Sigma-)/sigma(K+Sigma0), expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+Sigma- reaction, large positive asymmetries are observed indicating the dominance of the K*-exchange. A large difference between the asymmetries for the K+Sigma- and K+Sigma0 reactions can not be explained by simple theoretical considerations.