Exclusive Photoproduction of the Cascade (Xi) Hyperons

We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.Comment: submitted to Phys. Rev.

Measurement of K-p radiative capture to γΛ and γΣ0 for pK- between 514 and 750 MeV/c

Differential cross sections for K- radiative capture in flight on the proton, leading to the γΛ and γΣ0 final states, have been measured at eight K- momenta between 514 and 750 MeV/c. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated K/π beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the γΣ0 final state is dominated by hyperon-resonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the γΛ final state, in contrast, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV

Determination of the quadratic slope parameter in eta -\u3e 3 pi(0) decay

We have determined the quadratic slope parameter α for η→3π0 to be α = -0.031(4) from a 99% pure sample of 106η→3π0 decays produced in the reaction π-p→nη close to the η threshold using the Crystal Ball detector at the AGS. The result is four times more precise than the present world data and disagrees with current chiral perturbation theory calculations by about four standard deviations

Determination of the quadratic slope parameter in eta -\u3e 3 pi(0) decay

We have determined the quadratic slope parameter α for η→3π0 to be α = -0.031(4) from a 99% pure sample of 106η→3π0 decays produced in the reaction π-p→nη close to the η threshold using the Crystal Ball detector at the AGS. The result is four times more precise than the present world data and disagrees with current chiral perturbation theory calculations by about four standard deviations