Hadronic charm production by protons and pions on iron

Thesis (Ph. D.)--University of Rochester. Dept. of Physics and Astronomy, 1984.An experiment to measure the production of prompt single muons by 350 GeV protons and 278 GeV pions on iron has been performed at Fermilab. The measurement was made using a heavily instrumented variable density target-calorimeter (beam dump) followed by a very large acceptance muon detector. These results have been used to study hadronic production of charmed particles. In 350 GeV proton interactions, prompt single and µ+ and µ- production are approximately equal. The charm production cross section is in the range of 20 to 40 µb/nucleon (most of the uncertainty being due to the uncertainty in the average semi-leptonic branching ratio B; in particular, B(1-B) σcharm = 1.57 ± .30 µb/nucleon for -1 F F ≈ (1-XF)5.0 ± .9. Charmed baryon production is allowed at the 10 µb/nucleon level. An upper limit on the charmed baryon cross section which is independent of the semi-leptonic branching ratio of charmed baryons has been calculated. Intrinsic charm appears to be ruled out by these data. Comparison to neutrino beam dump experiments, using the same model and branching ratio assumptions, favors an A1.0 dependence for the charm cross section. Comparison to the NA16 experiment at CERN also indicates A1.0 dependence. In 278 GeV π- interactions, prompt single µ- production is larger than prompt single µ+ production by almost a factor of two. The source of the µ- excess has not been firmly established. One possible explanation, which enjoys some support from NA16 data, is the recombination of valence quarks from the beam pion with charmed quarks about 25% of the time. The xF distribution of charmed particles produced via recombination appears to be considerably flatter than charmed particles produced without recombination. If this picture is correct, then the ratio of the semi-leptonic branching ratios of charged to neutral D's is greater than 1.8 (90% confidence level). The total charm cross section is in the range 15 to 30 µb/nucleon (xF > 0), where most of the uncertainty comes from the uncertainty in the average semi-leptonic branching ratio B(1-B) σcharm = 1.29 +.40/-.29 µb/nucleon for xF > 0). Comparison with other pion experiments favors, as for protons, an A1.0 dependence of the charm cross section