Source radii at target rapidity from two-proton and two-deuteron correlations in central Pb+Pb collisions at 158 A GeV

Abstract

Two-proton and two-deuteron correlations have been studied in the target fragmentation region of central Pb+Pb collisions at 158 A GeV. Protons and deuterons were measured with the Plastic Ball spectrometer of the WA98 experiment at the CERN SPS. The results of one-dimensional and multi-dimensional analyses using both the Bertsch-Pratt and Yano-Koonin-Podgoretsky parameterizations of the two-particle correlation functions are presented. The proton source exhibits a volume emission, while the deuteron source, with small outward radius, appears opaque. Both proton and deuteron sources have cross-terms R_{ol}^2 and longitudinal velocities beta consistent with zero, indicating a boost-invariant expansion. The invariant radius parameter R follows an approximate A/sqrt{m} scaling while the longitudinal and transverse radii, R_{L} and R_{T}, scale approximately as A/sqrt{m_{T}} with A ~ 3 fm GeV^{1/2} in both cases.