Transverse Momentum and Angular Distributions of Hadrons in Muon-Proton Scattering and Tests of Quantum Chromodynamics

The properties of the transverse momenta and angular distributions of hadrons produced in muon-proton scattering are compared with first-order quantum-chromodynamics calculations. The quantum-chromodynamics prediction for the $Q^2$ dependence of the average hadron transverse momentum squared agrees with the data provided a constant term is added in quadrature to the prediction. This additive term is attributed to the intrinsic transverse momentum of the quarks in the nucleon and to the transverse momentum inherent in quark fragmentation.