S. Chapman et al., THE OUT-LONGITUDINAL CROSS TERM AND OTHER MODEL-INDEPENDENT FEATURES OF THE 2-PARTICLE HBT CORRELATION-FUNCTION, Nuclear physics. A, 590(1-2), 1995, pp. 449-452
Using two specific models and a model independent formalism, we show t
hat an ''out-longitudinal'' cross term should be included in any gauss
ian fits to correlation data. In addition, we show that correlation ra
dii (including the cross term) measure lengths of homogeneity within t
he source, not necessarily geometric sizes.