Robert Victor Cadman

Measurement of the total and differential cross sections for the reaction π−p → ηn with the Crystal Ball detector

The first results obtained in 1998 by the Crystal Ball collaboration from a measurement of the total and differential cross sections for the reaction π−p → ηn are presented. These new experimental results for the total cross sections are compared with the predictions of the K-matrix model for pion-nucleon scattering. The angular distribution at momenta near the reaction threshold (685 MeV/c) is determined by the S-wave contribution. The P-wave contribution begins to manifest itself from a momentum of 720 MeV/c.

Measurement of the total cross section of the reaction K{sup -}p{yields}{sigma}{sup 0}{gamma} between 514 and 750 MeV/c

We report the first measurements of the total cross section of the reaction K{sup -}p{yields}{sigma}{sup 0}{gamma} at eight beam momenta from 514 to 750 MeV/c. The data were obtained at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory using the Crystal Ball detector consisting of 672 NaI crystals. All charged particles were vetoed by a barrel of plastic scintillators, resulting in a study of only the neutral decays of the {sigma}{sup 0}. The prompt photon and the photons from the decay products of {sigma}{sup 0} were detected for each reconstructed event; the neutron was also detected in a small fraction of the events.

Measurement of the K{sup -}p{yields}{sigma}{sup 0}{pi}{sup 0} reaction between 514 and 750 MeV/c

The reaction K{sup -}p{yields}{sigma}{sup 0}{pi}{sup 0}{yields} neutrals was studied with the Crystal Ball detector at the BNL Alternating Gradient Synchrotron for beam momenta between 514 and 750 MeV/c. The photons from {sigma}{sup 0} and {pi}{sup 0} decays were detected, as well as the neutron in a small fraction of the events. The differential cross section and the {sigma}{sup 0} polarization are reported at eight momenta and nearly the full angular range. Total cross sections are derived from Legendre polynomial fits to the data. The measurements presented are of considerably higher precision than previous results.The reaction K- p → Σ 0 π 0 → neutrals was studied with the Crystal Ball detector at the BNL Alternating Gradient Synchrotron for beam momenta between 514 and 750 MeV/c. The photons from Σ0 and π 0 decays were detected, as well as the neutron in a small fraction of the events. The differential cross section and the Σ 0 polarization are reported at eight momenta and nearly the full angular range. Total cross sections are derived from Legendre polynomial fits to the data. The measurements presented are of considerably higher precision than previous results.

The Longitudinal Spin Program at STAR

The STAR Collaboration has nearly completed installation of electromagnetic calorimetry covering the full azimuth and pseudorapidity range −1 < η < 2. These calorimeters are essential for the STAR spin program, which requires efficient triggers for high‐pT jets, mesons, and photons. The results of this program will constrain Δg, the gluon contribution to the proton spin.