A Study Of Leading ∧ And △～(++) Production In P-Pb Collisions At 19 GeV/c And An Analysis Of Non-Uniform Longitudinal Flow In Relativistic Heavy Ion Collisions

Projectile proton fragmentation in p + A interactions has been an interesting physics topic because it is related to the dynamics of baryon number transport in nuclear collisions. At present there is no comprehensive understanding of the dynamics.E941 is an unique experiment for the leading particle measurement and study. It has the ability of measuring neutron and has large coverage of forward rapidity region. Invariant multiplicity distributions and dn/dy of the leading hyperon (A) and resonance (A++) have been measured in minimum bias p+Pb collisions at 19 GeV/c with the E864/E941 spectrometer at the ACS. The experimental acceptance for the measurement covers a region of 2.2 < y < 3.4 and 0.2 GeV/c < pr <1.1 GeV/c for the measurement of A and A++. Comparisons of the A and A++ yields with the leading proton and neutron yields measured by the sameexperiment and with other experimental data will shed light on the fragmentation of the incident proton associated with the production of various baryons in p + A interactions.The cross section for baryon flavor change is large and strongly depends on rapidity. This is very different from the expectation of simple diquark-quark fragmentation of incident proton. A suppression of leading A production in the forward rapidity region compared with the non-strange leading baryons is also observed. The relative probability of the projectile proton fragmentation into A++ and neutron is found to be about 35% in the region of 2.7