INFLUENCE OF RESONANCES ON BOSE-EINSTEIN CORRELATIONS OF IDENTICAL PIONS

The influence of resonances on narrow pair correlations of identical pions is considered in detail. It is shown that kinematic or dynamic restrictions on resonance momenta lead to a substantial anisotropy of the correlation function; variables allowing one to reveal this anisotropy are proposed. An upper estimate of 0.23 for the fraction of "directly" produced pions is obtained based on experimental data on the resonance yields in high-energy hadron interactions. It is shown that experimental data on like-pion correlations agree with a dominant contribution of the pions from the decays of light resonances. In particular, the observed value of the parameter-lambda characterizing the suppression of the interference effect, the decrease of the slope of the correlation function with increase in the relative momentum Q of the like pions in their c.m.s. and the dependence of the time parameter-tau on the pion velocity are explained. It is shown that the slope of the correlation function for the like-pion pairs containing the decay pions at Q > 0.1 GeV/c is mainly determined by the size of the resonance production region, which allows one to determine the size of the production region of "direct" particles (pions and resonances) despite the very low fraction of the pairs of "directly" produced pions. The fraction of "directly" produced pions, 0.17 +/- 0.09 (stat.) +/- 0.08 (syst.), and the radius of the "direct" production region, 0.55 +/- 0.08 (stat.) +/- 0.10 (syst.) fm, have been determined based on the analysis of the most accurate correlation function measured in pp- and ppBAR-interactions on ISR at 63 GeV.