Joshua Davies

A bstract: We compute the complete top-quark-induced next-to-leading order electroweak corrections to the form factors entering gluon-induced Higgs boson pair production. We consider the top quark contribution in the limit where the Mandelstam variables are much larger than all other scales involved in the process and compute about a hundred expansion terms in analytic form. They are used to obtain precise numerical results even for fairly low values of the transverse momentum of the Higgs boson. We show that these electroweak corrections at high energies are of the order of −10%. We also discuss the leading logarithmic corrections of the analytic expressions.

A bstract: We implement the recently-calculated analytic expressions for the next-to-leading order QCD corrections to gg → ZH in ggxy. This provides a flexible framework for investigating partonic and hadronic cross sections for various top quark mass renormalization schemes. We augment the Z boson with leptonic decays, including spin correlations and off-shell effects, and furthermore provide an interface to POWHEG. This enables simulations with parton showers, performed using Pythia.

A bstract: We compute two-loop corrections to the associated production of a Higgs boson with a Z boson and to off-shell Z boson pair production in the gluon fusion channel, mediated by a heavy quark. We perform deep expansions in the high-energy region and around the forward limit and show that their combination covers the whole phase space. Our results constitute the next-to-leading order virtual corrections to these processes. Their numerical evaluation is fast and the dependence on all parameters is maintained, thus a change of parameter values or renormalization scheme is straightforward. As a by-product of our calculation, we also obtain the two-loop heavy quark mediated virtual corrections to the processes of off-shell di-photon and photon- Z production.

A bstract: We compute three-loop virtual corrections to the associated production of a Higgs boson with a Z boson in the large- m _t limit. We describe in detail the application of the asymptotic expansion and provide, for all form factors, analytic results for the first three terms in the 1/ m _t expansion. We also provide numerical routines implemented in the C++ library ggxy.

We present state-of-the-art predictions for the inclusive cross section of gluon-initiated ZH Z H production, following the recommendations of the LHC Higgs Working Group. In particular, we include NLO QCD corrections, where the virtual corrections are obtained from the combination of a forward expansion and a high-energy expansion, and the real corrections are exact. The expanded results for the virtual corrections are compared in detail to full numerical results. The updated predictions show a reduction of the scale uncertainties to the level of 15%, and they include an estimate of the top-mass-scheme uncertainty.

We consider electroweak corrections to Higgs boson pair production, taking into account the top quark Yukawa and Higgs boson self couplings. Using differential equations we compute a deep expansion of all master integrals in the high-energy limit and present analytic results for the two-loop box-type form factors. We show that precise numerical results can be obtained even for relatively small values of the Higgs boson transverse momentum. We compare against recent numerical results and find good agreement.

In this talk I report on progress towards the computation of the next-to-next-to-leading order virtual corrections to Higgs boson pair production in gluon fusion, in an expansion around the forward-scattering limit. The results of this computation will provide an estimate of the size and uncertainty of the three-loop virtual corrections in a comparatively much larger region of phase space than the results available in the literature, which are based on an expansion in the limit of a large top quark mass.

A bstract: We compute three-loop corrections to the process gg → HH originating from one-particle reducible diagrams. This requires the computation of two-loop corrections to the gluon-gluon-Higgs vertex with an off-shell gluon. We describe in detail our approach to obtain semi-analytic results for the vertex form factors and present results for the two form factors contributing to Higgs boson pair production.