Longitudinal Momentum Fraction X_L for Two High P_t Protons in pp->ppX Reaction

We present an analysis of new data from Experiment E850 at BNL. We have characterized the inclusive cross section near the endpoint for pp exclusive scattering in Hydrogen and in Carbon with incident beam energy of 6 GeV. We select events with a pair of back-to-back hadrons at large transverse momentum. These cross sections are parameterized with a form $\frac{d \sigma}{d X_{L}}$ $\sim(1-X_{L})^{p}$, where ${X_{L}}$ is the ratio of the longitudinal momentum of the observed pair to the total incident beam momentum. Small value of $p$ may suggest that the number of partons participating in the reaction is large and reaction has a strong dependence on the center-of-mass energy. We also discuss nuclear effects observed in our kinematic region.Comment: 4 pages, 2 figures, to be published in Proceedings of CIPANP2000, Quebec, May 22-28, 2000, requires aipproc.sty(included

Measurement of color transparency by C(p,2p) reactions at large momentum transfer

The subject of color transparency, the enhancement of the ability of hadrons to penetrate nuclear matter by kinematic selection, is both interesting and controversial. The description of the collision of hadrons with nucleons inside nuclei, and the connection with initial and final state interactions involve fundamental questions of quantum mechanics, and nuclear and particle physics. Interest in color transparency was greatly increased by AGS Experiment 834 which observed dramatic changes with incident momentum for a variety of nuclei. A new experiment, E850, has studied the (p,2p) quasi-elastic reaction near 90{degree} cm for momenta between 5.9 and 9 GeV/c. The quasi-elastic reaction was compared to the elastic reaction on free protons to determine the transparency. With limited statistics, but with better kinematic definition in a new detector, the authors have confirmed the rise in Carbon transparency ratio seen in Expt 834. The Tr(D/H) for deuterium is consistent with no energy dependence. Unlike the free d{sigma}/dt for hydrogen, the d{sigma}/dt from protons in a nucleus is consistent with the exact s{sup {minus}10} scaling. This suggests two components to the pp scattering amplitude; one small and perturbative, the other spatially large and varying, but filtered away by the nuclear matter in the Carbon nucleus. The plan is to complete the repairs of the superconducting solenoid early this fall, reassemble the detector, and collect data starting next spring