Charm Production by Muons and Its Role in Scale-Noninvariance

摘要

Interactions of 209 GeV muons in the Multimuon Spectrometer at Fermilab have yielded more than 8 x 10 exp 4 events with two muons in the final state. After reconstruction and cuts, the data contain 20,072 events with (81 +- 10)% attributed to the diffractive production of charmed states decaying to muons. The cross section for diffractive charm muoproduction is 6.9(+1.9,-1.4) nb where the error includes systematic uncertainties. Extrapolated to Q exp 2 = 0 with sigma(Q exp 2 ) = sigma(0)(1 + Q exp 2 / lambda exp 2 ) exp -2 , the effective cross section for 178 (100) GeV photons is 750(+180,-130) (560(+200,-120)) nb and the parameter lambda is 3.3 +- 0.2 (2.9 +- 0.2) GeV/c. The nu dependence of the cross section is similar to that of the photon-gluon-fusion model. A first determination of the structure function for diffractive charm production indicates that charm accounts for approximately 1/3 of the scale-noninvariance observed in inclusive muon-nucleon scattering at low Bjorken x. Okubo-Zweig-Iizuka selection rules and unitarity allow the muon data to set a 90%-confidence lower limit on the psi N total cross section of 0.9 mb. (ERA citation 06:017630)