Searcharxiv⌕ Search

arXiv subjects

Nikolaos Kidonakis

Publications and source records attributed to Nikolaos Kidonakis.

161 records · Page 9Linked to original sources
arXiv1999

Soft-gluon resummation and NNLO corrections for direct photon production

The resummation of threshold logarithms for direct photon production cross sections in hadronic collisions is presented. The resummation is based on the factorization properties of the cross section and is formulated at next-to-leading logarithmic or higher accuracy. Full analytical and numerical results for the next-to-next-to-leading order expansion of the resummed cross section are given. A substantial reduction of factorization scale dependence is observed. A comparison to experimental results from the E-706 and UA-6 experiments is presented.

hep-ph↗
arXiv1999

Electroweak-boson hadroproduction at large transverse momentum: factorization, resummation, and NNLO corrections

We study the resummation of singular distributions for electroweak-boson production at large transverse momentum in hadronic collisions. We describe the factorization properties of the cross section near partonic threshold and construct the resummed cross section at next-to-leading logarithmic accuracy in moment space in terms of soft gluon anomalous dimensions. We present full analytical results for the expansion of the resummed cross section up to next-to-next-to-leading order. Our results can be applied to W, Z, and virtual gamma production at hadron colliders.

hep-ph↗
arXiv1999

Resummation for direct photon and W + jet production

I discuss the resummation of soft gluon contributions to direct photon and W + jet production and I present some results for the next-to-next-to-leading order expansions of the resummed cross sections for these processes near threshold.

hep-ph↗
arXiv1999

Soft gluon resummation for heavy quark and dijet cross sections

We discuss the resummation of threshold logarithms for heavy quark and dijet cross sections in hadronic collisions. The resummed cross sections are presented at next-to-leading logarithmic accuracy in terms of anomalous dimension matrices which describe the factorization of soft gluons from the hard scattering. We apply our formalism to the calculation of the top quark production cross section at the Fermilab Tevatron.

hep-ph↗
arXiv1999

Resummation for heavy quark and jet cross sections

We review the resummation of threshold logarithms for heavy quark, dijet, direct photon, and W boson production cross sections in hadronic collisions. Beyond leading logarithms the resummed cross section is sensitive to the color exchange in the hard scattering. The resummation is formulated at next-to-leading logarithmic or higher accuracy in terms of anomalous dimension matrices which describe the factorization of soft gluons from the hard scattering. We give results for the soft anomalous dimension matrices at one loop for the full range of partonic subprocesses involved in heavy quark, dijet, direct photon, and W boson production. We discuss the general diagonalization procedure that can be implemented for the calculation of the resummed cross sections, and we give numerical results for top quark production at the Fermilab Tevatron. We also present analytical results for the one- and two-loop expansions of the resummed cross sections.

hep-ph↗
arXiv1998

Soft-gluon resummation for heavy quark production in hadronic collisions

We discuss the heavy quark production cross section near partonic threshold in hadronic collisions, including the resummation of leading and next-to-leading logarithms arising from soft gluon emission. We show how to handle the complications due to the non-universal non-leading logarithms. We give analytical results for the $q {\bar q}$ partonic subprocess and numerical results in the DIS scheme for top quark production at the Fermilab Tevatron where the $q {\bar q}$ channel dominates.

hep-ph↗
arXiv1998

NLL Resummation for Dijet Production

We discuss threshold resummation for dijet production in hadronic collisions. Resummation to next-to-leading logarithmic (NLL) accuracy is given in terms of an anomalous dimension matrix for each partonic subprocess involved.

hep-ph↗
arXiv1998

Evolution of Color Exchange in QCD Hard Scattering

In QCD hard scattering cross sections, the color content of the underlying hard scattering evolves with a factorization scale. This evolution is controlled by an anomalous dimension matrix, specific to each hard-scattering reaction. Anomalous dimensions are determined from the renormalization of products of ordered exponentials of the gauge field, which describe the coherent radiation of gluons by incoming hadrons and the observed jets or particles of the final state. The anomalous dimensions depend on the kinematics of the underlying hard scattering, but are free of collinear singularities. A number of these matrices are available in the literature. Here, we exhibit one-loop mixing matrices for the full list of $2 \to 2$ reactions involving light quarks and gluons. The eight-by-eight anomalous dimension matrix for gluon-gluon scattering shows a simplified structure in the basis corresponding to definite color exchange in the $t$-channel.

hep-ph↗
arXiv1998

Threshold Resummation for Dijet Cross Sections

We construct dijet differential cross sections at large momentum transfer, in which threshold logarithms have been summed to all orders in perturbation theory. This extends previous work on heavy quark production, by treating collinear singularities associated with hard, massless partons in the final state. The resummed corrections enable us to define, in the sense of factorization, the underlying color exchange mechanism. The influence of color exchange on the resummed cross section is contained in the eigenvalues and eigenvectors of an anomalous dimension matrix, which describes the factorization of coherent soft gluons from the hard scattering. The precise formulas depend on the partonic scattering angles and energies, as well as on the method used to define the jets in the final state. For cone dijets at fixed invariant mass, we find leading logarithmic corrections that, like those in the Drell-Yan process, are positive, and which grow with increasing dijet invariant mass. Other choices of dijet cross section can give, however, qualitatively different behavior, even at leading logarithm.

hep-ph↗
arXiv1997

Threshold Resummation for QCD Hard Scattering

We describe the resummation of singular distributions at partonic threshold in heavy quark production, generalizing results for Drell-Yan and other electroweak hard-scattering processes.

hep-ph↗
arXiv1997

Resummation for QCD Hard Scattering

We resum distributions that are singular at partonic threshold (the elastic limit) in heavy quark production, in terms of logarithmic behavior in moment space. The method may be applied to a variety of cross sections sensitive to the edge of phase space, including transverse momentum distributions. Beyond leading logarithm, dependence on the moment variable is controlled by a matrix renormalization group equation, reflecting the evolution of composite operators that represent the color structure of the underlying hard scattering. At next-to-leading logarithmic accuracy, these evolution equations may be diagonalized, and moment dependence in the cross section is a sum of exponentials. Beyond next-to-leading logarithm, resummation involves matrix-ordering. We give a detailed analysis for the case of heavy quark production by light quark annihilation and gluon fusion.

hep-ph↗
arXiv1996

Resummation in Heavy Quark and Jet Cross Sections

We discuss corrections from the elastic limit (partonic threshold) in hadronic hard-scattering cross sections. We show why these corrections can be large at all orders in perturbation theory, and describe their resummation to arbitrary logarithmic accuracy. In particular, we discuss the role of color exchange in the hard scattering. This enables us to generalize the resummation of the Drell-Yan cross section to QCD reactions. As an example, we give the explicit resummed hard-scattering cross section for heavy-quark production through light quark annihilation, which takes into account next-to-leading logarithms to all orders.

hep-ph↗
arXiv1996

QCD resummation and heavy quark cross sections

In this dissertation a detailed analysis of heavy quark production is given with an emphasis on the resummation of soft gluon corrections. First we calculate the production cross sections for top quark production at the Fermilab Tevatron and for bottom quark production at fixed-target $pp$ experiments, and in particular HERA-B. We consider both the order $α_s^3$ cross sections and the resummation of soft gluon corrections in all orders of QCD perturbation theory. Then we calculate the inclusive transverse momentum and rapidity distributions for top quark production at the Fermilab Tevatron and bottom quark production at HERA-B. We give both $α_s^3$ and resummed results. Finally, we discuss the resummation of distributions that are singular at the elastic limit of partonic phase space (partonic threshold) in QCD hard-scattering cross sections, such as heavy quark production. We show how nonleading soft logarithms exponentiate in a manner that depends on the color structure within the underlying hard scattering. This result generalizes the resummation of threshold singularities for the Drell-Yan process, in which the hard scattering proceeds through color-singlet annihilation. We illustrate our results for the case of heavy quark production by light quark annihilation and gluon fusion, and also for light quark production through gluon fusion.

hep-ph↗
arXiv1996

On the Resummation of Singular Distributions in QCD Hard Scattering

We discuss the resummation of distributions that are singular at the elastic limit of partonic phase space (partonic threshold) in QCD hard-scattering cross sections, such as heavy quark production. We show how nonleading soft logarithms exponentiate in a manner that depends on the color structure within the underlying hard scattering. This result generalizes the resummation of threshold singularities for the Drell-Yan process, in which the hard scattering proceeds through color-singlet annihilation. We illustrate our results for the case of heavy quark production by light quark annihilation, and briefly discuss its extension to heavy quark production through gluon fusion.

hep-ph↗