The ring imaging Cherenkov detector for the BRAHMS experiment at RHIC

A ring imaging Cherenkov counter, to be read out by four 100-channel PMTs, is a key element of the BRAHMS experiment. We report here the most recent results obtained tested at the BNL AGS using several radiator gases, including the heavy fluorocarbon C4F10. Ring radii were measured for different particles (pions, muons, and electrons) for momenta ranging from 2 to 12 GeV/c employing pure C4F10 as radiator.Comment: 3 pages 3 figure

Measurement of quasi-elastic 12C(p,2p) scattering at high momentum transfer

We measured the high-momentum quasi-elastic 12C(p,2p) reaction (at center of mass angle near 90 degrees) for 6 and 7.5 GeV/c incident protons. The three-momentum components of both final state protons were measured and the missing energy and momentum of the target proton in the nucleus were determined. The validity of the quasi-elastic picture was verified up to Fermi momenta of about 450 MeV/c, where it might be questionable. Transverse and longitudinal Fermi momentum distributions of the target proton were measured and compared to independent particle models which do not reproduce the large momentum tails. We also observed that the transverse Fermi distribution gets wider as the longitudinal component increases in the beam direction, in contrast to a simple Fermi gas model.Comment: 4 pages including 3 figure

In-beam Tests of a Ring Imaging Cerenkov Detector With a Multianode Photomultiplier Readout

A ring-imaging \v{C}erenkov counter read out by a 100-channel PMT of active area 10$\times$10 cm$^2$ was operated successfully in a test beam at the BNL AGS with several radiator gases, including the heavy fluorocarbon C$_4$F$_{10}$. Ring radii were measured for electrons, muons, pions and kaons over the particle momentum range from 2 to 12 GeV/$c$, and a best resolution of $\sigma_r/r = 2.3\%$ was obtained.Comment: 11 pages (LaTeX) plus 7 figures in Postscript (gz-compressed and uuencoded

Thermal excitation of heavy nuclei with 5-15 GeV/c antiproton, proton and pion beams

Excitation-energy distributions have been derived from measurements of 5.0-14.6 GeV/c antiproton, proton and pion reactions with $^{197}$Au target nuclei, using the ISiS 4$\pi$ detector array. The maximum probability for producing high excitation-energy events is found for the antiproton beam relative to other hadrons, $^3$He and $\bar{p}$ beams from LEAR. For protons and pions, the excitation-energy distributions are nearly independent of hadron type and beam momentum above about 8 GeV/c. The excitation energy enhancement for $\bar{p}$ beams and the saturation effect are qualitatively consistent with intranuclear cascade code predictions. For all systems studied, maximum cluster sizes are observed for residues with E*/A $\sim$ 6 MeV.Comment: 14 pages including 5 figures and 1 table. Accepted in Physics Letter B. also available at http://nuchem.iucf.indiana.edu