Higgs production in association with a top-antitop pair in the Standard Model Effective Field Theory at NLO in QCD

Abstract:We consider the transverse-momentum distribution of a Higgs boson produced through gluon fusion in hadron collisions. At small transverse momenta, the large logarithmic terms are resummed up to next-to-leading-logarithmic (NLL) accuracy. The resummed computation is consistently matched to the next-to-leading-order (NLO) result valid at large transverse momenta. The ensuing Standard Model prediction is supplemented by possible new-physics effects parametrised through three dimension-six operators related to the modification of the top and bottom Yukawa couplings, and to the inclusion of a point-like Higgs-gluon coupling, respectively. We present resummed transverse-momentum spectra including the effect of these operators at NLL+NLO accuracy and study their impact on the shape of the distribution. We find that such modifications, while affecting the total rate within the current uncertainties, can lead to significant distortions of the spectrum. The proper parametrization of such effects becomes increasingly important for experimental analyses in Run II of the LHC.

“…[97][98][99][100] and [101,102], respectively. Strategies for extracting information on the Higgs-gluon couplings from the measurements were studied in ref.…”

Section: Jhep03(2017)115mentioning

confidence: 99%

Modeling BSM effects on the Higgs transverse-momentum spectrum in an EFT approach

Grazzini

Ilnicka

Spira

et al. 2017

“…The computation of NLO QCD corrections to top-quark processes involving anomalous couplings or higher-dimension operators has evolved in recent years [5,6,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. In particular automated calculations within MG5 aMC have been performed in [5,6,43,46,47], and…”

Section: Jhep10(2017)096mentioning

confidence: 99%

“…Such a calculation is an interesting one in itself: unlike the previous NLO EFT calculations in refs. [5,6,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], in this work the EFT is used in a top-down way, by starting from explicit BSM models, performing matching calculations at the same accuracy, employing RG equations down to the scale of the problem, and physical results are obtained by carrying out an NLO calculation there.…”

Section: Jhep10(2017)096mentioning

confidence: 99%

“…In this work we use the automated framework based on MG5 aMC. Calculations at NLO with higher-dimensional operators have been recently performed for the top-quark sector of the SMEFT [5,6,43,46,47]. For example, in ref.…”

Section: Calculation and Automationmentioning

confidence: 99%

“…For example, in ref. [47] predictions for pp → tth are obtained at NLO in QCD for O tG and the SM Higgs O HG operators. The approach has the advantage that results are fully exclusive, automatically matched to PS through MC@NLO [60], and can be directly used in experimental analyses.…”

Section: Calculation and Automationmentioning

confidence: 99%

See 2 more Smart Citations

Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

Franzosi

Vryonidou

Zhang

2017

Self Cite

Scalar and pseudo-scalar resonances decaying to top quarks are common predictions in several scenarios beyond the standard model (SM) and are extensively searched for by LHC experiments. Challenges on the experimental side require optimising the strategy based on accurate predictions. Firstly, QCD corrections are known to be large both for the SM QCD background and for the pure signal scalar production. Secondly, leading order and approximate next-to-leading order (NLO) calculations indicate that the interference between signal and background is large and drastically changes the lineshape of the signal, from a simple peak to a peak-dip structure. Therefore, a robust prediction of this interference at NLO accuracy in QCD is necessary to ensure that higher-order corrections do not alter the lineshapes. We compute the exact NLO corrections, assuming a point-like coupling between the scalar and the gluons and consistently embedding the calculation in an effective field theory within an automated framework, and present results for a representative set of beyond the SM benchmarks. The results can be further matched to parton shower simulation, providing more realistic predictions. We find that NLO corrections are important and lead to a significant reduction of the uncertainties. We also discuss how our computation can be used to improve the predictions for physics scenarios where the gluon-scalar loop is resolved and the effective approach is less applicable.

New physics from high energy tops

Farina

Mondino

Pappadopulo

et al. 2019

Precision measurements of high energy top quarks at the LHC constitute a powerful probe of new physics. We study the effect of four fermion operators involving two tops and two light quarks on the high energy tail of the tt invariant mass distribution. We use existing measurements at a center of mass energy of 13 TeV, and state of the art calculations of the Standard Model contribution, to derive bounds on the coefficients of these operators. We estimate the projected reach of the LHC at higher luminosities and discuss the validity of these limits within the Effective Field Theory description. We find that current measurements constrain the mass scale of these operators to be larger than about 1-2 TeV, while we project that future LHC data will be sensitive to mass scales of about 3-4 TeV. We apply our bounds to constrain composite Higgs models with partial compositeness and models with approximate flavor symmetries. We find our limits to be most relevant to flavor non-universal models with a moderately large coupling of the heavy new physics states to third generation quarks.