Cross-Section Measurements for Charm Production by 209-GeV Muons

Interactions of 209-GeV muons in the multimuon spectrometer at Fermilab have yielded 20 072 dimuon final states, with (81±10)% attributed to production of charmed states decaying to muons. The cross section for diffractive charm muoproduction is ${6.9}_{-1.4\mathrm{}}^{+1.9\mathrm{}}$ nb. Extrapolated to $Q^2=0\mathrm{}$, the effective cross section for 178- (100-) GeV photons is ${750}_{-130\mathrm{}}^{+180\mathrm{}}$ (${560}_{-120\mathrm{}}^{+200\mathrm{}}$) nb.