Two-particle rapidity correlations from the Bose-Einstein effect in central Si-28+Au collisions at 14.6A GeV/c and intermittency

In previous work, the E802 Collaboration at the BNL-AGS used negative binomial distribution (NBD) fits to charged particle multiplicity distributions from central collisions of O-16+Cu at 14.6A GeV/c to derive the two-particle short-range rapidity correlation length and strength. These turned out to be much shorter and weaker than the values for hadron collisions, which led to a simple and elegant explanation of intermittency. In the present work, a direct measurement of the two-particle correlation of identified pions in the E802/E859 magnetic spectrometer is performed in the interval 1.5 less than or equal to y less than or equal to 2.0 for central Si-28+Au collisions, both in terms of Q(inv) = root\(q) over right arrow\(2)-q(0)(2), where q = p(2)-p(1) = ((q) over right arrow, q(0)) and also in terms of \eta(2) - eta(1)\ and \y(2)-y(1)\, where p, eta, and y are the four-momentum, pseudorapidity, and rapidity of the pions. It is demonstrated that the two-pion correlation in rapidity (and pseudorapidity) is entirely due to the Bose-Einstein interference. The directly measured correlation length in both eta and y is xi = 0.19 +/- 0.03 for two pi(-), with strength R(0,0)similar to 1%, in agreement with the previous E802 indirect measurements derived from the NBD analysis of intermittency.