Zeitschrift für Physik C Particles and Fields

ISSN: 0170-9739 (printed version)
ISSN: 1431-5858 (electronic version)

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Abstract Volume 73 Issue 1 (1996) pp 119-124

Charmonium production via fragmentation at higher orders in <alpha>_s

P. Ernström, P. Hoyer, M. Vänttinen

NORDITA, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark

Received: 2 February 1996

Abstract. 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 <eta>_c shows that the higher-order process q->q<eta>_c in fact dominates the lowest-order process q->qg<eta>_c.

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