Check of the gluon-reggeization condition in the next-to-leading order: Gluon part

The last bootstrap condition whose validity has not been verified to date is considered. This condition is an indispensable element in the unitarity-relation-based proof of themulti-Regge form of highenergy gluon-exchange QCD amplitudes in the next-to-leading-logarithm approximation. The approach used here relies on the s-channel unitarity and makes it possible to reproduce successively, in all orders of perturbation theory, themulti-Regge form of the amplitude, provided that specific nonlinear relations, called bootstrap conditions, hold. All of them were derived, and all, with the exception of one, were tested. An explicit verification of fulfillment of the last condition (the bootstrap condition for the inelastic amplitude of the production of one gluon inmulti-Regge kinematics) is performed. In our preceding study, we performed such a verification for purely fermion contributions, while, in the present study, we complete it for one-loop gluon corrections to the components of the condition being considered.     

On the next-to-leading order Debye screening mass in QGP

The next-to-leading order Debye screening mass in QGP is calculated by taking into account the damping rate of gluons in the formalism of real time finite temperature QCD, and the infrared singularity of the naive calculation is cured without adding a nonperturbative magnetic screening mass as a cutoff. In addition, the result is shown to be postive and gauge-independent, and is compared with the results from lattice simulations.     

On the next-to-leading order Debye screening mass in QGP

The next-to-leading order Debye screening mass in QGP is calculated by taking into account the damping rate of gluons in the formalism of real time finite temperature QCD, and the infrared singularity of the naive calculation is cured without adding a nonperturbative magnetic screening mass as a cutoff. In addition, the result is shown to be postive and gauge-independent, and is compared with the results from lattice simulations.     

Exclusive decay to double at next-to-leading order in

Within the non-relativistic QCD (NRQCD) factorization framework, we calculate the exclusive decay process η_b→J/ψJ/ψ to next-to-leading order in the strong coupling constant, and, at leading order, in the charm quark relative velocity. It is found that this new contribution to the amplitude is comparable in magnitude to the previously calculated relativistic correction piece, but differs by a phase of about 90°. Including this new contribution will increase the previous prediction of substantially, thus brightening the discovery potential of this clean hadronic decay channel of η_b in the forthcoming LHC experiment.     

Heavy quark diffusion in perturbative QCD at next-to-leading order

We compute the momentum diffusion coefficient of a heavy quark in a hot QCD plasma, to next-to-leading order in the weak-coupling expansion. Corrections arise at [see formula]; physically they represent interference between overlapping scatterings, as well as soft, electric scale (p approximately gT) gauge field physics, which we treat using the hard thermal loop effective theory. In 3-color, 3-flavor QCD, the momentum diffusion constant of a fundamental representation heavy quark at next-to-leading order is kappa = 16pi/3alpha(s)(2)T(3)(ln1/g(s)+0.07428+1.9026 g(s)). The convergence of the perturbative expansion is poor.     

Single jet photoproduction at HERA in next-to-leading order QCD

We present results for next-to-leading order calculations of single jet inclusive cross sections by resolved photons inep-collisions at HERA. The dependence on the jet recombination cut and on the choice of the renormalization and factorization scales is studied in detail.     

Inclusive jet production with virtual photons in next-to-leading order QCD

We present a next-to-leading order calculation for the virtual photoproduction of one and two jets inep collisions. Soft and collinear singularities are extracted using the phase space slicing method. The collinear photon initial state singularity depends logarithmically on the mass of the virtual photon and is absorbed into the virtual photon structure function. An $\overline {MS} $ factorization scheme is defined similarly to the real photon case. Numerical results are presented for HERA conditions using the Snowmass jet definition for inclusive single jet and dijet cross sections. We study the dependence of these cross sections on the transverse energies and rapidities of the jets. Finally, we compare the ratio of the experimentally defined resolved and direct cross sections with recent ZEUS data as a function of the photon virtualityP ².     

Multijet cross sections in deep inelastic scattering at next-to-leading order

We present the perturbative prediction for three-jet production cross section in deep inelastic scattering at the next-to-leading order accuracy. We study the dependence on the renormalization and factorization scales of exclusive three-jet cross section. The perturbative prediction for the three-jet differential distribution as a function of the momentum transfer is compared to the corresponding data obtained by the H1 Collaboration at HERA.     

Three-jet cross sections in hadron-hadron collisions at next-to-leading order

We present a new QCD-event generator for hadron colliders which can calculate one-, two-, and three-jet cross sections at next-to-leading order accuracy. We study the transverse energy spectrum of three-jet hadronic events using the k(radially) algorithm. We show that the next-to-leading order correction significantly reduces the renormalization and factorization scale dependence of the three-jet cross section.