Deep-inelastic scattering on intrinsic charm quarks in the proton

Possibilities of probing the predicted intrinsic charm quark component in the proton by deep-inelastic lepton scattering are investigated. Total cross sections are found to be sizable, but the observable rate, e.g., through muons from semileptonic charm decays, depends strongly on the experimental situation. The DESY $\mathrm{ep}$ collider HERA has acceptance losses close to the proton beam, along which the $\mathrm{ep}$ system is strongly boosted, whereas for fixed target muon scattering, e.g., at Fermilab, the acceptance can be made much better. Backgrounds are calculated and ways to suppress them developed, resulting in acceptable signal/background ratios. For existing experiments the predicted statistics are relatively small, but may still contribute to a solution of the open intrinsic charm problem, whereas a dedicated experiment should settle the issue.