INCLUSIVE PRODUCTION OF PI(0) MESONS IN CC AND CCU COLLISIONS AT AN INCIDENT MOMENTUM OF 4.5 GEV C PER NUCLEON/

The cross sections for the inclusive production of pi(0) mesons in the reactions C + C --> pi(0) + x and C + Cu --> pi(0) + x at an incident momentum of 4.5 GeV/c are measured as functions of the cumulative num ber X. From the ratio of the observed cross sections for pi(0) product ion on carbon and copper targets in the interval 0.9 less than or equa l to X less than or equal to 1.9, the exponent in the cross-section pa rametrization Ed(3) sigma/d(3)p similar to A(T)(n) is derived to be n = 0.38 +/- 0.03. Under the assumption that the invariant cross section as a function of the projectile atomic number Ap can be parametrized in the form Ed(3) sigma/d(3)p similar to A(P)(m), the X and p(perpendi cular to)(2) dependences of the exponent m are investigated by compari ng the cross sections for the reactions C + A(T) --> pi(0) + x (A(T) = C, Cu) with those for the analogous reactions induced by incident a p articles. At X = 1.9, the parameter nt is found to reach a value of 2. 1 +/- 0.1. In the kinematical region specified by the inequalities the ta(pi) less than or equal to 16 degrees and E-pi greater than or equal to 2 GeV, the A(P) dependence of the cross section under study shows a significant variation with X and only a weak variation with the pion transverse momentum. The probabilities of the formation of six-quark configurations in He-4 and C-12 nuclei are estimated at 5% and 20%, re spectively. For the parametrization Ed(3) sigma/d(3)p similar to exp(- X/X-0), the values of the slope parameter X-0 corresponding to various energies of helium and carbon projectiles are compared. The energy at which the cross section reaches the scaling regime corresponding to a plateau in the energy dependence of the parameter X-0, which characte rizes the quark-parton structure function of the nucleus, is found to increase with increasing atomic weight of the nucleus undergoing fragm entation.