Top-pair production at the LHC through NNLO QCD and NLO EW

Self Cite

116

Abstract:We calculate the complete-NLO predictions for ttW ± and tttt production in proton-proton collisions at 13 and 100 TeV. All the non-vanishing contributions of O(α i s α j ) with i + j = 3, 4 for ttW ± and i + j = 4, 5 for tttt are evaluated without any approximation. For ttW ± we find that, due to the presence of tW → tW scattering, at 13(100) TeV the O(α s α 3 ) contribution is about 12(70)% of the LO, i.e., it is larger than the so-called NLO EW corrections (the O(α 2 s α 2 ) terms) and has opposite sign. In the case of tttt production, large contributions from electroweak tt → tt scattering are already present at LO in the O(α 3 s α) and O(α 2 s α 2 ) terms. For the same reason we find that both NLO terms of O(α 4 s α), i.e., the NLO EW corrections, and O(α 3 s α 2 ) are large (±15% of the LO) and their relative contributions strongly depend on the values of the renormalisation and factorisation scales. However, large accidental cancellations are present (away from the threshold region) between these two contributions. Moreover, the NLO corrections strongly depend on the kinematics and are particularly large at the threshold, where even the relative contribution from O(α 2 s α 3 ) terms amounts to tens of percents.

Section: Jhep02(2018)031mentioning

confidence: 99%

“…[18,31] and in refs. [19,25] for the calculation of the complete-NLO corrections. The code will soon be released and further documented in a detailed dedicated paper [32].…”

Section: Jhep02(2018)031mentioning

confidence: 99%

Large NLO corrections in t t ¯ W ± $$ t\overline{t}{W}^{\pm } $$ and

Frederix

Pagani

Zaro

2018

Self Cite

116

“…The most complete Standard Model predictions for differential cross sections combine next-to-next-leading-order (NNLO) QCD corrections with NLO electroweak (EW) ones [2]. In this paper we will focus exclusively on QCD corrections, with the understanding that the results can eventually be combined with EW corrections which have been studied extensively in the literature [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Section: Jhep05(2018)149mentioning

confidence: 99%

Resummation for (boosted) top-quark pair production at NNLO+NNLL′ in QCD

Czakon

Ferroglia

Heymes

et al. 2018

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We construct predictions for top quark pair differential distributions at hadron colliders that combine state-of-the-art NNLO QCD calculations with double resummation at NNLL accuracy of threshold logarithms arising from soft gluon emissions and of small mass logarithms. This is the first time a resummed calculation at full NNLO+NNLL accuracy in QCD for a process with non-trivial color structure has been completed at the differential level. Of main interest to us is the stability of the M tt and top-quark p T distributions in the boosted regime where fixed order calculations may become strongly dependent JHEP05 (2018)149 on the choice of dynamic scales. With the help of numeric and analytic arguments we confirm that the choice for the factorization and renormalization scales advocated recently by some of the authors is indeed optimal. We further derive a set of optimized kinematicsdependent scales for the matching functions which appear in the resummed calculations. Our NNLO+NNLL prediction for the top-pair invariant mass is significantly less sensitive to the choice of factorization scale than the fixed order prediction, even at NNLO. Notably, the resummed and fixed order calculations are in nearly perfect agreement with each other in the full M tt range when the optimal dynamic scale is used. For the top-quark p T distribution the resummation performed here has less of an impact and instead we find that upgrading the matching with fixed-order from NLO+NNLL to NNLO+NNLL to be an important effect, a point to be kept in mind when using NLO-based Monte Carlo event generators to calculate this distribution.

“…The "bulk" region is parameterized on a grid which is specified by equally spaced points in β 5) and two additional points close to the high energy boundary. The point β 80 = 0.999 is sufficient for LHC with 8 TeV center-of-mass energy, which was the extent of the interpolation grid of the spin summed calculation.…”

Section: Jhep03(2018)085mentioning

confidence: 99%

“…Considering the hadronic production of stable top-quark pairs, the prediction from Quantum Chromodynamics (QCD) is compelete to next-to-next-to leading order (NNLO) for the total cross section [1] and for differential distributions [2][3][4]. More recently NLO corrections from electroweak interactions [5,6] were also incorporated. A more complete modelling of pair production including decay and off-shell effects is available to NLO accuracy in QCD [7,8] in the case of the di-lepton channel and more recently also for the semi-leptonic channel [10].…”

Section: Introductionmentioning

confidence: 99%

Polarized double-virtual amplitudes for heavy-quark pair production

Chen

Czakon

Poncelet

2018

We present the two-loop virtual amplitudes for heavy-quark pair production in light quark-antiquark annihilation and gluon fusion channels, including full spin and color dependence. We use expansions around kinematical limits and numerical integration to obtain results for the involved master integrals. From these, we determine the renormalised infrared finite remainders of the coefficients of amplitude decompositions in terms of color and spin structures. The remainders are given in form of numerical interpolation grids supported by expansions around the production threshold and the high energy limit. Finally, we provide the spin density matrix, which encodes the heavy-quark spin correlations and is sufficient for phenomenological applications. Our results are necessary for the derivation of top-quark pair production cross sections in hadron collisions in the narrow width approximation with next-to-next-to-leading order accuracy in QCD.