Hard gluon bremsstrahlung in $\mu p$ scattering produces final-state hadrons with a large component of momentum transverse to the virtual-photon direction. Quantum chromodynamics can be used to predict not only the absolute value of the transverse momentum, but also its angular distribution relative to the muon scattering plane. The angular correlations should be insensitive to nonperturbative effects.

• Received 25 October 1977

DOI:https://doi.org/10.1103/PhysRevLett.40.3