Charm production by muons and its role in scale noninvariance

Interactions of 209-GeV muons in the multimuon spectrometer at Fermilab have yielded more than 8×104 events with two muons in the final state. After reconstruction and cuts, the data contain 20 072 events with (8110)% attributed to the diffractive production of charmed states decaying to muons. The cross section for diffractive charm muoproduction is 6.9-1.4+1.9 nb where the error includes systematic uncertainties. Extrapolated to Q2=0 with (Q2)=(0)(1+Q22)-2, the effective cross section for 178- (100-) GeV photons is 750-130+180 (560120200) nb and the parameter is 3.30.2 (2.90.2) GeV/c. The dependence of the cross section is similar to that of the photongluon-fusion model. Okubo-Zweig-Iizuka selection rules and unitarity allow the muon data to set a 90%-confidence lower limit on the N total cross section of 0.9 mb. A first determination of the structure function F2(cc») for diffractive charm production indicates that charm accounts for approximately 13 of the scale noninvariance observed in inclusive muon-nucleon scattering at low Bjorken x.