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

Le résumé fourni par la source

High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\Sigma}}^{0}$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the ${K}^{+}$ production angle. Independent measurements were made using the ${K}^{+}p{\ensuremath{\pi}}^{\ensuremath{-}}$($\ensuremath{\gamma}$) and ${K}^{+}p$(${\ensuremath{\pi}}^{\ensuremath{-}},\ensuremath{\gamma}$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR, and LEPS results, while offering better statistical precision and a 300-MeV increase in $\sqrt{s}$ coverage. Above $\sqrt{s}\ensuremath{\approx}2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward and backward angles, respectively. Our recoil polarization (${P}_{\ensuremath{\Sigma}}$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles, we find that ${P}_{\ensuremath{\Sigma}}$ is of the same order of magnitude but opposite sign as ${P}_{\ensuremath{\Lambda}}$, in agreement with the static SU(6) quark model prediction of ${P}_{\ensuremath{\Sigma}}\ensuremath{\approx}\ensuremath{-}{P}_{\ensuremath{\Lambda}}$. This expectation is violated in some mid- and backward-angle kinematic regimes, where ${P}_{\ensuremath{\Sigma}}$ and ${P}_{\ensuremath{\Lambda}}$ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial-wave analyses being performed to search for missing baryon resonances.

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