Joint rapidity and multiplicity dependences of correlation functions in high-energy collisions

Using language of statistical mechanics, we discuss the agreement between two-particle correlations at fixed multiplicity (canonical ensemble) and correlations defined inclusively (grand ensemble), with particular emphasis on the corrections to asymptotic equality expected for these observables. It is furthermore shown that multiperipheral models with predominantly positive correlations imply asymptotically the increase of two-particle semi-inclusive correlation functions with increasing $n$ near $〈 n 〉$. Recent data at $205 \frac{\mathrm{GeV}}{c}$ do not confirm these expectations, and alternative interpretations are discussed.