BACKWARD PROTON PRODUCTION IN PI(-GEV() AND K+ COLLISIONS WITH AL ANDAU NUCLEI AT 250)C/

Backward proton production is studied in interactions of pi(+) and Kmesons with Al and Au nuclei at 250 CeV/c, The proton momentum spectra are measured at different emission angles. From the two-proton correl ations, it is found, that a significant part ((26+/-4)% for Al and (44 +/-6)% for Au) of the backward proton production can be attributed to secondary pion absorption by a nucleon pair in the nuclear medium, pi( +)(pn) --> (p) over left arrow p and pi(0)(pp) --> (p) over left arrow p. It is found that the share of the secondary pion absorption can be fitted by a power dependence proportional to A(beta), with beta = 0.2 7+/-0.05. An upper limit of the cross section for the colour-charge-ex change mechanism of backward proton production is estimated.