Charmonium Production via Fragmentation at Higher Orders in α s
نویسندگان
چکیده
Quarkonium production at a given large p T is dominated by parton fragmentation: a parton which is produced with transverse momentum p T /z fragments into a quarkonium state which carries a fraction z of the parton momentum. Since parton production cross sections fall steeply with p T , high z fragmentation is favored. However, quantum number constraints may require the emission of gluons in the fragmentation process, and this softens the z dependence of the fragmentation function. We discuss the possibility that higher-order processes may enhance the large z part of fragmentation functions and thus contribute significantly to the quarkonium cross section. An explicit calculation of light quark fragmentation into η c shows that the higher-order process q → qη c in fact dominates the lowest-order process q → qgη c .
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