Differential Cross Section and Photon-Beam Asymmetry for theγ→n→K+Σ−Reaction atEγ<

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 E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 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 K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Differential cross sections and recoil polarizations for the reactionγp→K+Σ0

“…0.7), there seems to be an initial dip in the cross section just after the 1.9-GeV peak and a subsequent rise, indicative of a smaller second peak around √ s ≈ 2.1 GeV. This feature was also pointed out in the previous CLAS analysis [14] and is present in the latest LEPS data [17] as well.…”

“…Previous high-statistics measurements for γp → K + 0 have been made by the CLAS [13][14][15], SAPHIR [16], LEPS [17,18], and GRAAL [19] Collaborations. The SAPHIR dσ/d cos θ K + c.m.…”

“…In addition to the observables reported here, the LEPS Collaboration [17] and the GRAAL Collaboration [19] have also measured photon-beam asymmetries for this channel, while the FROST experiment at CLAS/JLab [21] will measure several other single-and double-polarization observables. The present work is part of a larger program within the CLAS Collaboration to make precision measurements for several photoproduction channels [22][23][24][25], with the goal of performing a coupled-channels partial-wave analysis (PWA).…”

Photoproduction of $\pi^{-}\Delta^{++}$ and $\pi^{+}\Delta^{0}$ on the proton for the comparison of $\bar{u}u$ and $\bar{d}d$ productions

“…Other charged meson photoproduction reactions from the proton, such as γ p → π + n [14,17] and γ p → K + Λ and K + Σ 0 [6,7,8,18,13], have positive asymmetries. It is interesting that only theūu quark pair production in the final state from the proton has negative asymmetries.…”

“…The LEPS spectrometer was designed to efficiently detect φ -mesons decaying to K + and K − at forward angles [1,2,3,4,5]. Not only φ but also K + photoproduction reactions are extensively studied [6,7,8,9,10,11,12,13].…”