On heavy quarks photoproduction and c #-># D"* fragmentation functions

The state of the art of the theoretical calculations for heavy quarks photoproduction is reviewed. The full fixed order next-to-leading order massive calculation and the resummation of large log(p_T/m) terms for differential cross sections are described. The implementation of a non-perturbative fragmentation function describing the c#->#D"* meson transition is also discussed. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Onium production

The present status of our understanding of onium production is reviewed. Different models are described and comparisons of theoretical prediction with experimental data are given. (orig.)11 refs.Available from TIB Hannover: RA 2999(96-144) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Heavy quarks photoproduction

The state of the art of the theoretical calculations for heavy quarks photoproduction is reviewed. The full next-to-leading order calculation and two possible resummations, the high energy one for total cross sections and the large p_T one for differential cross sections, are described. (orig.)7 refs.Available from TIB Hannover: RA 2999(96-145) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Phenomenology of quarkonia production in fixed target experiments and at the Tevatron and HERA colliders

The phenomenology of heavy quarkonia production in fixed target experiments and at the Tevatron and HERA colliders is reviewed. The latest theoretical results are presented and compared with data, with emphasis on the predictions of the factorization approach by Bodwin, Braaten and Lepage. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Charm photoproduction via fragmentation

The next-to-leading open charm production in #gamma#p collisions is calculated within the Perturbative Fragmentation Functions formalism, to allow resummation of #alpha#_s log(p_T"2/m"2) terms. In the large p_T region (p_T>m) the result is consistent with the fixed order NLO calculation, small discrepancies being found for very large p_T and at the edge of phase space. The two approaches differ in the definition and the relative contribution of the direct and resolved terms, but essentially agree on their sum. The resummation is found to lead to a reduced sensitivity to the choice of the renormalization/factorization scale. (orig.)18 refs.Available from TIB Hannover: RA 2999(95-103) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

D"* production from e"+e"- to ep collisions in NLO QCD

Fragmentation functions for D mesons, based on the convolution of a perturbative part, related to the heavy quark perturbative showering, and a non-perturbative model for its hadronization into the meson, are used to describe D"* production in e"+e"- and ep collisions. The non-perturbative part is determined by fitting the e"+e"- data taken by ARGUS and OPAL at 10.6 and 91.2 GeV respectively. When fitting with a non perturbative Peterson fragmentation function and using next-to-leading evolution for the perturbative part, we find an #epsilon# parameter significantly different from the one commonly used, which is instead found with a leading order fit. The use of this new value is shown to increase considerably the cross section for D"* production at HERA, suggesting a possible reconciliation between the next-to-leading order theoretical predictions and the experimental data. (orig.)28 refs.Available from TIB Hannover: RA 2999(97-029) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Associated J/#psi# + #gamma# photoproduction as a probe of the colour-octet mechanism

The associated production of a J/#psi# and a photon in photon-hadron collisions is considered, and shown to be a good probe of the presence of colour-octet mediated channels in quarkonia production, as predicted by the factorization approach within NRQCD. Total and differential cross sections for photoproduction at fixed target experiments and at HERA are presented. Associated J/#psi# + #gamma# production at hadron colliders is briefly discussed. (orig.)28 refs.Available from TIB Hannover: RA 2999(96-147) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Large-p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o heavy quark production in two-photon collisions

The next-to-leading-order (NLO) cross section for the production of heavy quarks at large transverse momenta (p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o) in #gamma##gamma# collisions is calculated with perturbative fragmentation functions (PFF's). This approach allows for a resummation of terms #propor to##alpha#_s ln(p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o "2/m"2) which arise in NLO from collinear emission of gluons by heavy quarks at large p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o or from almost collinear branching of photons or gluons into heavy-quark pairs. We present single-inclusive distributions in p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o and rapidity including direct and resolved photons for #gamma##gamma# production of heavy quarks at e"+e"- colliders and at high-energy #gamma##gamma# colliders. The results are compared with the fixed-order calculation for m finite including QCD radiative corrections. The two approaches differ in the definitions and relative contributions of the direct and resolved terms, but essentially agree in their sum. The resummation of the #alpha#_s ln(p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o "2/m"2) terms in the PFF approach leads to a softer p _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o distribution and to a reduced sensitivity to the choice of the renormalization and factorization scales. (orig.)26 refs.Available from TIB Hannover: RA 2999(95-205) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

NLO production and decay of quarkonium

We present a calculation of next-to-leading-order (NLO) QCD corrections to total hadronic production cross sections and to light-hadron-decay rates of heavy quarkonium states. Both colour-singlet and colour-octet contributions are included. We discuss in detail the use of covariant projectors in dimensional regularization, the structure of soft-gluon emission and the overall finiteness of radiative corrections. We compare our approach with the NLO version of the threshold-expansion technique recently introduced by Braaten and Chen. Most of the results presented here are new. Others represent the first independent reevaluation of calculations already known in the literature. In this case a comparison with previous findings is reported. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Charmed mesons fragmentation functions

Fragmentation functions for heavy-light mesons, like the charmed D, D"* mesons, are proposed. They are based on next-to-leading QCD perturbative fragmentation functions for heavy quarks, with the addition of a non-perturbative term describing phenomenologically the quark#->#meson transition. The cross section for production of large p_T D, D"* mesons at the Tevatron is evaluated in this framework. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(96-146) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman