Inclusive production of D mesons in photon-photon collisions at and 189 GeV and a first measurement of
EUROPEAN PHYSICAL JOURNAL C(2000)
摘要
The inclusive production of D*(+/-) mesons in photon-photon collisions has been measured using rile OPAL detector at LEP at e(+)e(-) centre-of-mass energies root S-ee of 183 and 189 GeV. The D*(+) mesons are reconstructed in their decay to D(0)pi(+) with the D-0 observed in the two decay modes K(-)pi(+) and K(-)pi(+)pi(-)pi(+) After background subtraction, 100.4 +/- 12.6 (stat) D*(+/-) mesons have been selected in events without observed scattered beam electron ("anti-tagged") and 29.8 +/- 5.9 (stat)D*(+/-) mesons in events where one beam electron is scattered into the detector ("single-tagged"). Direct and single-resolved events are studied separately. Differential cross-sections d sigma/dp(T)(D*) and d sigma/d \eta(D*)\ as functions of the D*+/- transverse momentum p(T)(D*) and pseudorapidity eta(D*) are presented in the kinematic region 2 GeV < p(T)(D*) < 12 GeV and \eta(D*)\ < 1.5 They are compared to next-to-leading order (NLO) perturbative QCD calculations. The total cross-section for the process e(+)e(-) --> e(+)e(-) c (c) over bar where the charm quarks are produced in the collision of two quasi-real photons is measured to be sigma(e(+)e(-) --> e(+)e(-) c (c) over bar) = 963 +/- 110 (stat) +/- 86 (sys) +/- 224 (extrapolation) pb. A first measurement. of the charm structure function F-2.0(gamma), of the photon is performed in the kinematic range 0.0014 < x < 0.87 and 5 GeV2 < Q(2) < 100 GeV2. and the result is compared to a NLO perturbative QCD calculation.
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关键词
structure function,centre of mass,cross section,background subtraction
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