Final state interactions for Bose-Einstein correlations in S+Pb to π^+π^+ +X reaction at energy 200GeV/nucleon

We applied an analytical formula for Bose-Einstein correlations (BEC) developed by us recently to high-energy heavy ion collisions, in particular to data on S+Pb$\to\pi^+$-$\pi^+$+X reaction at energy $200$ GeV/nucleon reported by the NA44 Collaboration. It takes into account both Coulomb and strong ($\pi$-$\pi$~s-wave; I=2) final state interactions (FSI). We have found that inclusion of the strong interaction in addition to Coulomb correction affects significantly the extracted parameters of the BEC like the source size $R$, the degree of coherence $\lambda$ and the long-range correlation parameter $\gamma$. In particular, the $\lambda$ parameter of the BEC is increased by about 20\%. Our results differ from those obtained in $e^+e^-$ annihilation in the following way: the $\lambda$ parameter does not reach `chaotic limit' and the $\gamma$ parameter does not approach to zero.