A QCD Analysis of Quark Recombination for Leading Particle Effect

The quark recombination mechanism is proposed to explain the asymmetry between production rates of $D^+$ and of $D^-$ in their inclusive productions, and also asymmetries for other charmed hadrons. These asymmetries are observed in experiment and are called as leading particle effects. In this work we give a general analysis for contributions of quark recombination to these asymmetries. The contributions consist of a perturbative- and nonperturbative part. We perform two types of factorization by considering the produced hadron with large transverse momentum and by taking charm quark as a heavy quark, respectively. In the case of large transverse momentum the effect of quark recombination is the standard twist-4 effect. We find that the contributions are parameterized with four nonperturbative functions, defined with four quark operators at twist-4, for initial hadrons without polarization. By taking charm quark as a heavy quark the factorization can be performed with the heavy quark effective theory(HQET). The effect of quark recombination is in general parameterized by eight nonperturbative parameters which are defined as integrals with matrix elements of four quark operators defined in HQET. For unpolarized hadrons in the initial state, the parameters can effectively be reduced to four. Perturbative parts in the two types of factorization are calculated at tree-level.
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