Search

Abstract We describe how the nested soft-collinear subtraction scheme [1] can be used to compute the next-to-next-to-leading order (NNLO) QCD corrections to the production of an arbitrary number of gluonic jets in hadron collisions. We show that the infrared subtraction terms can be combined into recurring structures that in many cases are simple iterations of those terms known from next-to-leading order. The way that these recurring structures are identified and computed is fairly general, and can be applied to any partonic process. As an example, we explicitly demonstrate the cancellation of all singularities in the fully-differential cross section for the q q ¯ $$ q\overline{q} $$ → X + Ng process at NNLO in QCD. The finite remainder of the NNLO QCD contribution, which arises upon cancellation of all ϵ-poles, is expressed via relatively simple formulas, which can be implemented in a numerical code in a straightforward way. Our approach can be extended to describe arbitrary processes at NNLO in QCD; the largest remaining challenge at this point is the combinatorics of quark and gluon collinear limits.

The ATLAS and CMS collaborations at the LHC have recently announced evidence for the rare Higgs boson decay into a Z boson and a photon. We analyze the interference between the process gg→H→Zγ induced by loops of heavy particles, which is by far the dominant contribution to the signal, and the continuum gg→Zγ QCD background process mediated by light quark loops. This interference modifies the event yield, the resonance line-shape and the apparent mass of the Higgs boson. We calculate the radiative corrections to this interference beyond the leading-order approximation in perturbative QCD and find that, while differing numerically from the corresponding effects on the more studied gg→γγ signal, they are generally rather small. As such, they do not impact significantly the interpretation of the present measurements of the H→Zγ decay mode.

Abstract In this paper we consider signal-background interference effects in Higgs-mediated diphoton production at the LHC. After reviewing earlier works that show how to use these effects to constrain the Higgs boson total decay width, we provide predictions beyond NLO accuracy for the interference and related observables, and study the impact of QCD radiative corrections on the Higgs width determination. In particular, we use the so-called soft-virtual approximation to estimate interference effects at NNLO in QCD. The inclusion of these effects reduces the NNLO prediction for the total Higgs cross-section in the diphoton channel by about 1.7%. We study in detail the impact of QCD corrections on the Higgs-boson line-shape and its implications for the Higgs boson width extraction. In particular, we find that the shift of the Higgs resonance peak arising from interference effects gets reduced by about 30% with respect to the NLO prediction. Assuming an experimental resolution of about 150 $$\textrm{MeV}$$ MeV on interference-induced modifications of the Higgs-boson line-shape, our NNLO analysis shows that one could constrain the Higgs-boson total width to about 10–20 times its Standard Model value.

Abstract We compute mixed QCD-electroweak corrections to the neutral-current Drell-Yan production of a pair of massless leptons in the high invariant mass region. Our computation is fully differential with respect to the final state particles. At relatively low values of the dilepton invariant mass, m ℓℓ ∼ 200 GeV, we find unexpectedly large mixed QCD-electroweak corrections at the level of −1%. At higher invariant masses, m ℓℓ ∼ 1 TeV, we observe that these corrections can be well approximated by the product of QCD and electroweak corrections. Hence, thanks to the well-known Sudakov enhancement of the latter, they increase at large invariant mass and reach e.g. −3% at m ℓℓ = 3 TeV. Finally, we note that the inclusion of mixed corrections reduces the theoretical uncertainty related to the choice of electroweak input parameters to below the percent level.