Recent results of charged pion and kaon photoproduction on the proton at SPring-8/LEPS

¹ for LEPS Collaboration - Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 Japan
² for LEPS Collaboration - Nagoya University, Furocho, Chikusa, Nagoya, 464-8602 Japan

^* Corresponding author: kohri@rcnp.osaka-u.ac.jp

Published online: 22 September 2020

Abstract

We carry out photoproduction experiments by using linearly polarized photon beams with energies of 1.5-3 GeV at SPring-8/LEPS. One of our physics motivations is to understand reaction mechanisms of hadron photoproduction. We study (1) y^→p→ π^-Δ⁺⁺, (2) y^→p→ π⁺n, (3) y^→p→ K⁺Λ(K⁺Σ⁰), and (4) y^→p→ π⁺Δ⁰ reactions which produce (1) uu, (2) dd, (3) ss, and (4) dd quark-antiquark pairs in the final state. Differential cross sections and photon beam asymmetries have been measured at forward meson angles of 0.6 < cos θ_cm <1. Precise comparison between the π^-Δ⁺⁺ and π⁺Δ⁰ reactions plays an important role in the study of nucleon resonances. It enables to distinguish between N* and Δ* by taking the cross section ratios of the two reactions. We have measured preliminary cross section ratios dσ(π⁺Δ⁰)/dσ(π^-Δ⁺⁺). The ratios are found to be close to 1/3, which is expected from the exchange of isospin=1 in the t channel, for 0.966< cos θ_cm <1 and all the photon energies. The ratios become larger than 1/3 and close to 1 for larger angles and higher energy regions. The larger ratios might be due to A resonances, giving the ratio 4/3, excited in the intermediate state