This paper presents results on charm photoproduction in the energy interval 40 to 160 GeV, obtained from the high-statistics charm samples of the NA 14/2 experiment at CERN. We measure the charm cross-section, the distributions inxF andp2T and various production ratios and charge asymmetries. The total non-diffractive open-charm cross-section per nucleon is measured to be\(\sigma _{(\gamma N \to c\bar cX)} \) at 〈Eγ〉 =100 GeV. We discuss the photoproduction of charm in terms of theoretical and phenomenological models. We compare the measuredp2T andxF distributions with first-order QCD calculations of photon-gluon fusion and obtain a value for the charm-quark mass ofmc=1.5+0.2−0.1GeV/c2.
D0 cross section assuming branching ratio of D0 --> K- PI+ of 3.65 +- 0.21 PCT.
D+(-) cross section assuming branching ratio of D+ --> K- PI+ PI+ of 8.0 +0.8,-0.7 PCT.
Total non diffractive open charm production cross section allowing for contributions for other charmed particles (D/S and LAMBDA/C). Comparison of data with first order QCD leads to a predicted charm quark mass of 1.5 +0.2,-0.1 GeV.
In a photoproduction experiment using a mean photon energy of 100 GeV we have observed 29±8 Λ c ( Λ c ) charmed-baryon and antibaryon decays in the pK − π + ( p K + π − ) final state. Quasi two-body final states do not contribite significantly to this channel. The mass of the Λ c was measured to be 2281.7±2.7±2.6 MeV/ c 2 and its lifetime 0.18±0.03±0.03 ps. The ratio of Λ c D production, measured in this experiment, is significantly greater than that predicted by photon-gluon fusion and using a Lund model to describe the hadronization. This excess cannot be completely accounted for in this model, even using a Λ c branching fraction in pK π as high as 5%.
Result extrapolated to all lambda/c energies has large model dependent uncertainties.
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