Slopes and breaks of transverse-momentum-squared distributions in 16 GeV/c π−p interactions

Distributions of transverse momentum squared of pions and protons produced in π−p collisions at 16 GeV/c are studied both for final states of different charged multiplicities and for the inclusive reaction. It is shown that all inclusive distributions have a characteristic concave shape that can be described by the sum of a steeper and a flatter exponential component, with crossing point at about pT2 = 0.2 (GeV/c)2. The study of the semi-inclusive reactions indicates that this two-component behaviour originates in low-multiplicity channels (nc ⩽ 6). The steep component of π+ and π− spectra for channels of low charged multiplicities are studied in detail by comparing the observed sharp dependence of the slope upon the effective mass of the nucleon-pion system, with the corresponding results obtained for Monte-Carlo events. It is found that energy/momentum conservations, together with limitation of transverse momenta, give a quantitative description of these results. However, to justify the relative amount of steep and flat components in the inclusive spectra, the dynamics of resonance production are to be considered.