The gamma + p to K+ + Lambda and gamma + p to K+ + Sigma0 reactions at forward angles with photon energies from 1.5 to 2.4 GeV

TL;DR

This study measures differential cross sections and photon beam asymmetries for gamma p to K+ Lambda and Sigma0 reactions at forward angles with photon energies from 1.5 to 2.4 GeV, revealing resonance structures and exchange contributions.

Contribution

First detailed measurements of these reactions at forward angles in this energy range, confirming resonance structures and analyzing exchange mechanisms.

Findings

Photon beam asymmetries are positive and increase with photon energy.

Differential cross sections agree with CLAS data but differ from SAPHIR at high cosTheta.

Resonance-like structure at W=1.96 GeV confirmed in K+Lambda reaction.

Abstract

Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda and gamma p rightarrow K+ Sigma0 reactions have been measured in the photon energy range from 1.5 GeV to 2.4 GeV and in the angular range from Theta_{cm} = 0 to 60 of the K+ scattering angle in the center of mass system at the SPring-8/LEPS facility. The photon beam asymmetries for both the reactions have been found to be positive and to increase with the photon energy. The measured differential cross sections agree with the data measured by the CLAS collaboration at cosTheta_{cm}<0.9 within the experimental uncertainties, but the discrepancy with the SAPHIR data for the K+Lambda reaction is large at cosTheta_{cm}>0.9. In the K+Lambda reaction, the resonance-like structure found in the CLAS and SAPHIR data at W=1.96 GeV is confirmed. The differential cross sections at forward angles suggest a strong K-exchange contribution in the t-channel for the K+Lambda reaction, but not for the K+Sigma0 reaction.