Light fermionic NNLO QCD corrections to top-antitop production in the quark-antiquark channel

We present the NNLO corrections to top pair production in the quark-antiquark channel proportional to the number of light quark flavors $N_l$. While the double real corrections were derived previously, here we compute the real-virtual and virtual-virtual contributions in this partonic channel. Using the antenna subtraction formalism, we show that the subtraction terms correctly approximate the real-virtual contributions in all their infrared limits. Combined with the integrated forms of the double real and real-virtual subtraction terms, we show analytically that the explicit infrared poles cancel at the real-virtual and virtual-virtual levels respectively, thereby demonstrating the validity of the massive extension of the NNLO antenna formalism. These NNLO corrections are implemented in a Monte Carlo parton level generator providing full kinematical information on an event-by event basis. With this program, NNLO differential distributions in the form of binned histograms are obtained and presented here.Comment: 42 pages, 8 figure

Radiative corrections to the photon + 1 jet rate at LEP

We present a complete calculation of the photon +1 jet rate in e(^+)e(^-) annihilation up to O(aa(_s)). Although formally of next-to-leading order in perturbation theory, this calculation contains several ingredients appropriate to a next-to-next-to-leading order calculation of jet observables. No such calculation has been performed before, and the work discussed here represents a first step in that direction. In particular, we describe a generalization of the commonly used phase space slicing method to isolate the singularities present when more than one particle is unresolved. More precisely, we provide an analytic evaluation of the following multiple unresolved factors: triple collinear factor, soft/collinear factor and double single collinear factor. By comparing the results of our calculation with the existing data on the photon +1 jet rate from the ALEPH Collaboration at CERN, we make a new determination of the process-independent non-perturbative quark-to-photon fragmentation function D(_q-γ)(z,μ(_F)) at O(aa(_s)). at As a first application of this measurement allied with our improved perturbative calculation, we determine the dependence of the isolated photon -fl jet cross section in a democratic clustering approach on the jet resolution parameter y(_cut) at next-to-leading order. Inclusion of the next-to-leading order corrections to this observable considerably improves the agreement between theoretical prediction and experimental data

NNLO Antenna Subtraction with One Hadronic Initial State

In this talk we present the extension of the antenna subtraction method to include initial states containing one hadron at NNLO. We sketch the requirements for the different necessary subtraction terms, and we explain how the antenna functions are integrated over the appropriate phase space by reducing the integrals to a small set of master integrals. Where applicable, our results for the integrated antennae were cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.Comment: 6 pages, 1 figure. Talk given at RADCOR 2009 - 9th International Symposium on Radiative Corrections (Applications of Quantum Field Theory to Phenomenology) October 25 - 30 200

Top quark pair production at NNLO in the quark-antiquark channel

We present the derivation of the NNLO two-parton final state contributions to top pair production in the quark-antiquark channel proportionnal to the leading colour factor $N_c^2$. Together with the three and four-parton NNLO contributions presented in a previous publication, this enables us to complete the phenomenologically most important NNLO corrections to top pair hadro-production in this channel. We derive this two-parton contribution using the massive extension of the NNLO antenna subtraction formalism and implement those corrections in a parton-level event generator providing full kinematical information on all final state particles. In addition, we also derive the heavy quark contributions proportional to $N_h$. Combining the new leading-colour and heavy quark contributions together with the light quark contributions derived previously, we present NNLO differential distributions for LHC and Tevatron. We also compute the differential top quark forward-backward asymmetry at Tevatron and find that our results are in good agreement with the measurements by the D0 collaboration.Comment: 48 pages, 9 figure

Antenna subtraction for the production of heavy particles at hadron colliders

The antenna subtraction method developed originally for the computation of higher order corrections to jet observables from a colourless initial state is extended for hadron collider processes involving a pair of massive particles and jets in the final state at the next-to-leading order (NLO) level. Due to the presence of coloured initial states, the subtraction terms need to be divided into three categories (final-final, initial-final and initial-initial). In this paper, we outline their construction and derive the necessary ingredients: phase space factorisation, antenna functions and also integrated antennae, including the effects of massive final states in all of those building parts. As a first application, we explicitly construct the colour-ordered real radiation and the corresponding antenna subtraction terms required at NLO for the production of a top quark pair and for the production of a top quark pair in association with a hard jet. The latter constitutes an essential ingredient for the computation of the hadronic production of a top-antitop pair at NNLO.Comment: 80 pages, LaTeX, version accepted for publication in JHE

Second order QCD corrections to gluonic jet production at hadron colliders

We report on the calculation of the next-to-next-to-leading order (NNLO) QCD corrections to the production of two gluonic jets at hadron colliders. In previous work, we discussed gluonic dijet production in the gluon-gluon channel. Here, for the first time, we update our numerical results to include the leading colour contribution to the production of two gluonic jets via quark-antiquark scattering.Comment: 8 pages, 4 figures, Proceedings of "Loops and Legs in Quantum Field Theory", Weimar April 201