Charm Hadron Production Fractions.pdf

a r X i v : h e p - e x / 9 9 1 2 0 6 4 v 1 2 7 D e c 1 9 9 9 Charm Hadron Production Fractions Leonid Gladilin ? ? Inst. of Experimental Physics II, University of Hamburg February 7, 2008 Abstract The world average values for the probabilities that a charm quark fragments into D?+ and D+ s have been calculated to be f(c → D?+) = 0.235± 0.007 (±0.007) and f(c → D+ s ) = 0.101± 0.009 (±0.025), respectively. The average values for D0, D+ and Λ+ c have been also calculated. ?gladilin@mail.desy.de ?On leave from Moscow State University, supported by GIF, contract I-0444-176.07/95 Introduction The probabilities that a charm quark fragments intoD?+, D+ s and other charm hadrons are not calculable in perturbative QCD. To obtain them one can use data on charm production in e+e? annihilations. The most comprehensive charm measurements were performed by the CLEO [1, 2] and ARGUS [3, 4, 5] collaborations at centre-of-mass energies of about 10GeV and by the OPAL [6, 7], ALEPH [8] and DELPHI [9, 10] collaborations in Z0 decays. We will use their measurements performed with charm hadrons reconstructed in the following decay modes1: D?+ → D0 π+ s → (K? π+) π+ s , (1) D+ s → φ π+ → (K? K+) π+, (2) D0 → K? π+, (3) D+ → K? π+ π+, (4) Λ+ c → p K? π+, (5) The Particle Data Group (PDG) branching ratios for the reference decay modes are [11]: B(D?+→ D0π+) = 0.683±0.014, B(D+ s → φπ+) = 0.036± 0.009, B(D0→ K?π+) = 0.0385±0.0009, B(D+→ K?π+π+) = 0.090± 0.006 and B(Λ+ c → pK?π+) = 0.050± 0.013. CLEO and ARGUS Measurements CLEO and ARGUS measurements are summarized in table 1. In the case if two errors are quoted then the first error is statistical and the second is systematic. The D+ s production cross sections are corrected for the branching ratio B(φ → K?K+) = 0.491±0.008 [11]. The total hadronic cross section at 10.55GeV was measured to be 3.33± 0.05± 0.21 nb [12]. In Ref. [1] the fraction of cc? in the total hadronic cross section was estimated with a Monte Carlo calculation to be