We present the first measurement of associated direct photon+muon productio
n in hadronic collisions, from a sample of 1.8 TeV <p(p)over bar> collision
s recorded with the Collider Detector at Fermilab. Quantum chromodynamics (
QCD) predicts that these events are primarily from the Compton scattering p
rocess cg-->c gamma, with the final state charm quark producing a muon. Hen
ce this measurement is sensitive to the charm quark content of the proton.
The measured cross section of 29+/-9 pb is compared to a leading-order QCD
parton shower model as well as a next-to-leading-order QCD calculation. [S0