Results on charm physics from WA82

Effective functional form of Regge trajectories

“…In π − Cu interactions at 230 GeV the ACCMOR collaboration [52] finds n = 3.23 ± 0.29 for leading charm production (and n = 4.34 ± 0.35 for nonleading, and n = 3.74 ± 0.23 for the combined data). For 340 GeV π − beam on Si, Cu and W targets the WA82 collaboration [53] finds n = 2.9 ± 0.3. Finally, for 250 GeV π − beam on Be, Al, Cu and W targets the E769 collaboration [54] finds n = 3.2 ± 0.5 on Al target, and n = 3.7 ± 0.4 for leading D production on all targets (and n = 4.0 ± 0.4 for nonleading, and n = 3.9 ± 0.3 for the combined data).…”

Production mechanisms of charm hadrons in the string model

“…We will here mainly consider the variation with x F , integrated over p ⊥ , since A does not vary much with p ⊥ over the experimental range of x F values [3,4]. The asymmetry in Pythia is compared to experiment in [2,3,4], and the model shows general agreement with experiment, except in the region 0 ≤ x F ≤ 0.4 where the model is predicting a larger asymmetry than found in the data. One collaboration [4] has tuned the parameters of…”

“…Asymmetries in the production spectra of charm and anticharm hadrons (or generally, asymmetries between leading and non-leading particles) have been observed since long [1]. But it is only in recent years [2,3,4] that the precision has improved so as to allow more detailed studies, especially in π − p events. Perturbative QCD calculations predict only very small asymmetries [5,6], so the origin of the observed asymmetries has to be sought in nonperturbative physics.…”

“…Charm cross sections are often presented as functions of Feynman-x, x F = p L /p L,max ≈ 2p L /E CM , i.e. the longitudinal momentum fraction of the meson in the rest frame of the event [2,3,4]. The x F distribution for the different production channels in the standard Lund model is shown in Fig.…”

“…For the π − the three cases correspond to < χ > = 0.14, 0.23 and 0.5 respectively. Also shown is data from [2,3,4]. above 1 GeV.…”