ESTIMATION OF HYDRODYNAMICAL MODEL PARAMETERS FROM THE INVARIANT SPECTRUM AND THE BOSE-EINSTEIN CORRELATIONS OF PI(-) MESONS PRODUCED IN (PI(+) K+)P INTERACTIONS AT 250 GEV/C/

The invariant spectra of pi(-) mesons produced in (pi(+)/K+)p interact ions 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 unde rgoes predominantly longitudinal expansion and non-relativistic transv erse expansion with mean transverse velocity [u(t)] = 0.20 +/- 0.07, a nd is characterized by a large temperature inhomogeneity in the transv erse 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 rapid ity distribution of the pion source is found to be Delta eta = 1.36 +/ - 0.02. Combining this estimate with results of the Bose-Einstein corr elation analysis in the same experiment, one extracts a mean freeze-ou t time of the source of [tau(f)] = 1.4 +/- 0.1 fm/c aad its transverse geometrical rms radius, R-G(rms)= 1.2 +/- 0.2 fm. (C) 1998 Elsevier S cience B.V.