Hyperon photoproduction in the nucleon resonance region

Abstract

High-statistics cross sections and recoil polarizations for the reactions ␥ + p → K + + ⌳ and ␥ + p → K + + ⌺ 0 have been measured at CLAS for center-of-mass energies between 1.6 and 2.3 GeV. In the K + ⌳ channel we confirm a resonance-like structure near W = 1.9 GeV at backward kaon angles. Our data show more complex sand u-channel behavior than previously seen, since structure is also present at forward angles, but not at central angles. The position and width change with angle, indicating that more than one resonance is playing a role. Large positive ⌳ polarization at backward angles, which is also energy dependent, is consistent with sizable s-or u-channel contributions. Presently available model calculations cannot explain these aspects of the data.

Photoproduction ofΛandΣ0hyperons using linearly polarized photons

“…A comprehensive set of measurements of differential cross sections, recoil polarizations and beam-recoil double polarisations, C x and C z , for the reactions γ p → K + and γ p → K + 0 has been carried out using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab [9][10][11][12][13]. Measurements of the beam asymmetry observable in these reactions have been reported by the LEPS [14] and GRAAL [15] Collaborations.…”

First Time Measurements of Polarization Observables for the Charged Cascade Hyperon in Photoproduction

“…Probing for narrow structures in P for the cascade must wait until enough data are available to bin more finely. Although not directly reported, the bin-integrated results of [48] "cancel" among bins to some degree, in particular for integrating forward and backward angles, which makes better correspondence with our results. In any case, our P results suggest the polarization mechanism for the cascade and Λ differ to some degree, although both mechanisms Interestingly, our observation of a small induced polarization for the cascade corresponds well with expectations derived from diquark considerations.…”

“…The near-zero integrated value of P differs significantly from what was reported for Λ production under similar conditions in Ref. [48], which showed prominent structure for γp → K + Λ for P , with values as high as ±0.5 for many bins. However, finer binning and statistical precision was achievable for the Λ analysis due to higher production cross sections.…”

Polarisation observables for strangeness photoproduction on a frozen spin target with CLAS at Jefferson Lab

“…Following the SAPHIR work, higher-statistics measurements of the cross sections for both the K + Λ and K + Σ reactions were made using CLAS [36,37]. These measurements covered centre-of-mass energies in the range 1.6 The CLAS data reproduces the overall structure of the SAPHIR results, although the K + Λ cross sections are somewhat larger.…”