Two-particle rapidity correlations from the Bose-Einstein effect in central {sup 28}Si+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 {sup 16}O+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{le}y{le}2.0 for central {sup 28}Si+Au collisions, both in terms of Q{sub inv}={radical}({vert_bar}{rvec q}{vert_bar}{sup 2}{minus}q{sub 0}{sup 2}), where q=p{sub 2}{minus}p{sub 1}=({rvec q},q{sub 0}), and also in terms of {vert_bar}{eta}{sub 2}{minus}{eta}{sub 1}{vert_bar} and {vert_bar}y{sub 2}{minus}y{sub 1}{vert_bar}, where p,{eta}, and {ital 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 {ital y} is {xi}=0.19{plus_minus}0.03 for two {pi}{sup {minus}}, with strength R(0,0){approximately}1{percent}, in agreement with the previous E802 indirect measurements derived from the NBD analysis of intermittency. {copyright} {ital 1997} {ital The American Physical Society}