Two-loop QCD helicity amplitudes for $g\,g \to Z\,g$ and $g\,g \to Z\,γ$

We present the O(α 3 s ) virtual QCD corrections to the process h → g +g +g due to interference of born and two-loop amplitudes, where h is a massive spin-2 particle and g is the gluon. We assume that the SM fields couple to h through the SM energy momentum tensor. Our result constitutes one of the ingredients to full NNLO QCD contribution to production of a massive spin-2 particle along with a jet in the scattering process at the LHC. In particular, this massive spin-2 could be a KK mode of a ADD graviton in large extra dimensional model or a RS KK mode in warped extra dimensional model or a generic massive spin-2. In addition, it provides an opportunity to study the ultraviolet and infrared structures of QCD amplitudes involving tensorial coupling resulting from energy momentum operator. Using dimensional regularization, we find that infrared poles of this amplitude are in agreement with the proposal by Catani confirming the factorization property of QCD amplitudes with tensorial insertion.

supporting

confidence: 69%

Two-Loop QCD correction to massive spin-2 resonance → 3 gluons

Ahmed

Mahakhud

Mathews

et al. 2014

“…The evolution factor U(µ h , µ) depends on the anomalous dimensions of the hard function. The construction of the hard function from the results for the four-point helicity amplitudes [15,16] is discussed in detail in [11]. It is obtained by squaring renormalized helicity amplitudes,…”

Section: Size Of the Perturbative Correctionsmentioning

confidence: 99%

“…The jet and soft functions were computed to two-loop order earlier in [12,13] and [14]. In our recent paper [11], we extracted the final ingredient for N 3 LL resummation, namely the two-loop hard function, from the results for the two-loop helicity amplitudes for theses processes [15,16].…”

Section: Introductionmentioning

confidence: 99%

The transverse-momentum spectrum of Higgs bosons near threshold at NNLO

Becher

Bell

Lorentzen

et al. 2014

Abstract:We give next-to-next-to-leading order (NNLO) predictions for the Higgs production cross section at large transverse momentum in the threshold limit. Near the partonic threshold, all radiation is either soft or collinear to the final state jet which recoils against the Higgs boson. We find that the real emission corrections are of moderate size, but that the virtual corrections are large. We discuss the origin of these corrections and give numerical predictions for the transverse-momentum spectrum. The threshold result is matched to the known NLO result and implemented in the public code PeTeR.

“…Once NNLO calculations of all diboson processes become publicly accessible, the uncertainties from all sources should be subsumed in the scale variation of the analogous NNLO calculations, with the exception of the gg initial state, which only first appears at NNLO. For this last part, two-loop results for γγ and ZZ already exist [45,46], as do most components of the Zγ calculation [70], allowing for a more robust characterization of the associated uncertainties than the estimates we have performed here.…”

Section: Z Decay and Lepton Isolationmentioning

confidence: 86%

Precision diboson observables for the LHC

Frye

Freytsis

Scholtz

et al. 2016

Motivated by the restoration of SU(2) × U(1) at high energy, we suggest that certain ratios of diboson differential cross sections can be used as high-precision observables at the LHC. We rewrite leading-order diboson partonic cross sections in a form that makes their SU(2) × U(1) and custodial SU(2) structure more explicit than in previous literature, and identify important aspects of this structure that survive even in hadronic cross sections. We then focus on higher-order corrections to ratios of γγ, Zγ and ZZ processes, including full next-to-leading-order corrections and gg initial-state contributions, and argue that these ratios can likely be predicted to better than 5%, which should make them useful in searches for new phenomena. The ratio of Zγ to γγ is especially promising in the near term, due to large rates and to exceptional cancellations of QCD-related uncertainties. We argue that electroweak corrections are moderate in size, have small uncertainties, and can potentially be observed in these ratios in the long run.