Estimation of hydrodynamical model parameters from the invariant spectrum and the Bose-Einstein correlations of π− mesons produced in (π+/K+)p interactions at 250 GeV/c

Abstract The invariant spectra of π − mesons produced in ( π + /K + )p interactions at 250 GeV/ c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity 〈 u t 〉=0.20±0.07, and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140±3 MeV and 82±7 MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Δη =1.36±0.02. Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of 〈 τ f 〉=1.4±0.1 fm/ c and its transverse geometrical rms radius, R G (rms)=1.2±0.2 fm.