Joao Pires

Second order QCD corrections to jet production at hadron colliders: the all-gluon contribution

We report the calculation of next-to-next-to-leading order QCD corrections in the purely gluonic channel to dijet production and related observables at hadron colliders. Our result represents the first next-to-next-to-leading order calculation of a massless jet observable at hadron colliders, and opens the path towards precision QCD phenomenology with the LHC.

NNLO QCD corrections to jet production at hadron colliders from gluon scattering

A bstractWe present the next-to-next-to-leading order (NNLO) QCD corrections to dijet production in the purely gluonic channel retaining the full dependence on the number of colours. The sub-leading colour contribution in this channel first appears at NNLO and increases the NNLO correction by around 10% and exhibits a pT dependence, rising from 8% at low pT to 15% at high pT. The present calculation demonstrates the utility of the antenna subtraction method for computing the full colour NNLO corrections to dijet production at the Large Hadron Collider.

Antenna subtraction for gluon scattering at NNLO

We use the antenna subtraction method to isolate the double real radiation infrared singularities present in gluonic scattering amplitudes at next-to-next-to-leading order. The antenna subtraction framework has been successfully applied to the calculation of NNLO corrections to the 3-jet cross section and related event shape distributions in electron-positron annihilation. Here we consider processes with two coloured particles in the initial state, and in particular two-jet production at hadron colliders such as the Large Hadron Collider (LHC). We construct a subtraction term that describes the single and double unresolved contributions from the six-gluon tree-level process using antenna functions with initial state partons and show numerically that the subtraction term correctly approximates the matrix elements in the various single and double unresolved configurations.

Double virtual corrections for gluon scattering at NNLO

A bstractWe use the antenna subtraction method to isolate the double virtual infrared singularities present in gluonic scattering amplitudes at next-to-next-to-leading order. In previous papers, we derived the subtraction terms that rendered (a) the double real radiation tree-level process finite in the single and double unresolved regions of phase space and (b) the mixed single real radiation one-loop process both finite and well behaved in the unresolved regions of phase space. Here, we show how to construct the double virtual subtraction term using antenna functions with both initial- and final-state partons which remove the explicit infrared poles present in the two-loop amplitude. As an explicit example, we write down the subtraction term for the four-gluon two-loop process. The infrared poles are explicitly and locally cancelled in all regions of phase space leaving a finite remainder that can be safely evaluated numerically in four-dimensions.

Perturbative QCD description of jet data from LHC Run-I and Tevatron Run-II

A bstractWe present a systematic comparison of jet predictions at the LHC and the Tevatron, with accuracy up to next-to-next-to-leading order (NNLO). The exact computation at NNLO is completed for the gluons-only channel, so we compare the exact predictions for this channel with an approximate prediction based on threshold resummation, in order to determine the regions where this approximation is reliable at NNLO. The kinematic regions used in this study are identical to the experimental setup used by recently published jet data from the ATLAS and CMS experiments at the LHC, and CDF and D0 experiments at the Tevatron. We study the effect of choosing different renormalisation and factorisation scales for the NNLO exact prediction and as an exercise assess their impact on a PDF fit including these corrections. Finally we provide numerical values of the NNLO k-factors relevant for the LHC and Tevatron experiments.

Transverse-momentum resummation for Higgs boson pair production at the LHC with top-quark mass effects

A bstractWe consider Higgs boson pair production via gluon fusion in hadronic collisions. We report the calculation of the transverse-momentum (qT ) distribution of the Higgs boson pair with top-quark mass (Mt) effects fully taken into account. At small values of qT we resum the logarithmically-enhanced perturbative QCD contributions up to next-to-leading logarithmic (NLL) accuracy. At intermediate and large values of qT we consistently combine resummation with the OαS3

p_{\rm T}

\mathcal{O}\left({\alpha}_S^3\right)

Second order QCD corrections to gluonic jet production at hadron colliders

fixed-order results. After integration over qT , we recover the next-to-leading order (NLO) result for the inclusive cross section with full dependence on Mt. We present illustrative numerical results at LHC energies, together with an estimate of the corresponding perturbative uncertainties, and we study the impact of the top-quark mass effects.