Damiano Tommasini

Transverse-momentum resummation: Higgs boson production at the Tevatron and the LHC

A bstractWe consider the transverse-momentum (qT ) distribution of Standard Model Higgs bosons produced by gluon fusion in hadron collisions. At small qT (qT ≪ mH , mH being the mass of the Higgs boson), we resum the logarithmically-enhanced contributions due to multiple soft-gluon emission to all order in QCD perturbation theory. At interme-diate and large values of qT (qT < mH), we consistently combine resummation with the known fixed-order results. We use the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-leading fixed-order calculation. We extend previous results including exactly all the perturbative terms up to order αS in our computation and, after integration over qT, we recover the known next-to-next-to-leading order result for the total cross section. We present numerical results at the Tevatron and the LHC, together with an estimate of the corresponding uncertainties. Our calculation is implemented in an updated version of the numerical code HqT.

Higgs boson production at the LHC: transverse momentum resummation effects in the H → γγ, H → WW → lνlν and H → ZZ → 4l decay modes

A bstractWe consider Standard Model Higgs boson production through gluon-gluon fusion in hadron collisions. We combine the calculation of the next-to-next-to-leading order QCD corrections to the inclusive cross section with the resummation of multiple soft-gluon emissions at small transverse momenta up to next-to-next-to-leading logarithmic accuracy. The calculation is implemented in the numerical program HRes and allows us to retain the full kinematics of the Higgs boson and of its decay products. We present selected numerical results for the signal cross section at the LHC (

The pentabox Master Integrals with the Simplified Differential Equations approach

\sqrt {s} = {8}\;{\text{TeV}}

On the reduction of generalized polylogarithms to Lin and Li2,2 and on the evaluation thereof

), in the H → γγ, H → WW → lνlν and H → ZZ → 4l decay channels by using the nominal cuts applied in current Higgs boson searches by the ATLAS and CMS collaborations.

Two-loop Master Integrals with the Simplified Differential Equations approach

A bstractWe present the calculation of massless two-loop Master Integrals relevant to five-point amplitudes with one off-shell external leg and derive the complete set of planar Master Integrals with five on-mass-shell legs, that contribute to many 2 → 3 amplitudes of interest at the LHC, as for instance three jet production, γ, V, H + 2 jets etc., based on the Simplified Differential Equations approach.

Master integrals and generalized polylogarithms: focus on fast and efficient evaluation

A bstractWe give expressions for all generalized polylogarithms up to weight four in terms of the functions log, Lin, and Li2,2, valid for arbitrary complex variables. Furthermore we provide algorithms for manipulation and numerical evaluation of Lin and Li2,2, and add codes in Mathematica and C++ implementing the results. With these results we calculate a number of previously unknown integrals, which we add in appendix C.

The gluon-fusion process

A bstractWe calculate the complete set of two-loop Master Integrals with two off massshell legs with massless internal propagators, that contribute to amplitudes of diboson V1V2 production at the LHC. This is done with the Simplified Differential Equations approach to Master Integrals, which was recently proposed by one of the authors.

On the reduction and evaluation of generalized polylogarithms

In the LHC era, precision QCD calculations have become a necessity. After the OPP method has been developed, the computation of particle cross sections and physical observables at NLO accuracy has become automated in many cases. Unfortunately, for some processes NLO accuracy is not enough and NNLO corrections are needed. In the recent period, substantial improvements in understanding amplitude reduction at two loops and computation of the necessary two-loop master integrals has been achieved. There is a general consensus that in the (near) future automation of NNLO calculations will be feasible and then the problem of reasonable computational cost of two loops contribution to NNLO cross section will become relevant. In this seminar I will focus on general features in evaluating master integrals, with emphasis on evaluating master integrals in different phase space regions (with Euclidean or physical particle momenta). Particular emphasis will be given on fast evaluation of generalized polylogarithms, since many master integrals are expressed in terms of such special functions.

On the evaluation and reduction of generalized polylogarithms

This Report summarises the results of the second years activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.