Charm Hadron Production Fractions

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 D, D and Λ c have been also calculated. [email protected] 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 ee 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 Z decays. We will use their measurements performed with charm hadrons reconstructed in the following decay modes: D → D π s → (K π) π s , (1) D s → φ π → (K K) π, (2) D → 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→ Dπ) = 0.683±0.014, B(D s → φπ) = 0.036± 0.009, B(D→ Kπ) = 0.0385±0.0009, B(D→ Kππ) = 0.090± 0.006 and B(Λ c → pKπ) = 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 → KK) = 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 cc̄ in the total hadronic cross section was estimated with a Monte Carlo calculation to be 0.37± 0.02 (syst.) and thus the total cross section into charm particles was calculated to be σ(c) = 2.46± 0.04(stat.)± 0.20(syst.)nb . (6) Dividing the measured values from table 1 by the total charm cross section and the branching ratio for the reconstruction mode, charm hadron production fractions have been obtained. The charge conjugated processes are also included.