Precision top pair production at hadron colliders

We demonstrate the impact of recent NNLO calculations on precision top quark phenomenology.Comment: Based on talks given at the 11th DESY Workshop "Loops and Legs in Quantum Field Theory 2012", the 7th International Workshop on the CKM Unitarity Triangle "CKM 2012" and the 5th International Workshop on Top Quark Physics "Top 2012

Top++: a program for the calculation of the top-pair cross-section at hadron colliders

We present the program Top++ for the numerical evaluation of the total inclusive cross-section for producing top quark pairs at hadron colliders. The program calculates the cross-section in a) fixed order approach with exact next-to-next-to leading order (NNLO) accuracy and b) by including soft-gluon resummation for the hadronic cross-section in Mellin space with full next-to-next-to-leading logarithmic (NNLL) accuracy. The program offers the user significant flexibility through the large number (29) of available options. Top++ is written in C++. It has a very simple to use interface that is intuitive and directly reflects the physics. The running of the program requires no programing experience from the user.Comment: v2.0: Major update: includes full NNLO result; functionality updates. Program webpage: http://www.alexandermitov.com/softwar

NNLO corrections to top pair production at hadron colliders: the quark-gluon reaction

We compute the next-to-next-to-leading order QCD correction to the total inclusive top pair production cross-section in the reaction qg \to t\bar t + X. We find moderate O(1%) correction to central values at both Tevatron and LHC. The scale variation of the cross-section remains unchanged at the Tevatron and is significantly reduced at the LHC. We find that recently introduced approximation based on the high-energy limit of the top pair cross-section significantly deviates from the exact result. The results derived in the present work are included in version 1.4 of the program Top++. Work towards computing the reaction gg\to t\bar t+X is ongoing.Comment: 17+1 pages, 6 figure

Percent level precision physics at the Tevatron: first genuine NNLO QCD corrections to q qbar -> t tbar + X

We compute the Next-to-Next-to-Leading Order (NNLO) QCD corrections to the partonic reaction that dominates top-pair production at the Tevatron. This is the first ever NNLO calculation of an observable with more than two colored partons, and/or massive fermions, at hadron colliders. Augmenting our fixed order calculation with soft-gluon resummation through Next-to-Next-to-Leading Logarithmic (NNLL) accuracy, we observe that the predicted total inclusive cross-section exhibits a very small perturbative uncertainty, estimated at +-2.7%. We expect that once all sub-dominant partonic reactions are accounted for, and work in this direction is ongoing, the perturbative theoretical uncertainty for this observable could drop below +-2%. Our calculation demonstrates the power of our computational approach and proves it can be successfully applied to all processes at hadron colliders for which high-precision analyses are needed.Comment: 4 pages, 4 figure

Resolving the Tevatron Top Quark Forward-Backward Asymmetry Puzzle: Fully Differential Next-to-Next-to-Leading-Order Calculation

We determine the dominant missing Standard Model (SM) contribution to the top quark pair forward-backward asymmetry at the Tevatron. Contrary to past expectations, we find a large, around 27%, shift relative to the well-known value of the inclusive asymmetry in next-to-leading order (NLO) QCD. Combining all known Standard Model corrections, we find that AFB^{SM} = 0.095 +- 0.007. This value is in agreement with the latest D0 measurement [V. M. Abazov et al. (D0 Collaboration), Phys. Rev. D 90, 072011 (2014)] AFB^{D0} = 0.106+- 0.03 and about 1.5 sigma below that of CDF [T. Aaltonen et al. (CDF Collaboration), Phys. Rev. D 87, 092002 (2013)] AFB^{CDF} =0.164 +- 0.047. Our result is derived from a fully differential calculation of the next-to-next-to leading order (NNLO) QCD corrections to inclusive top pair production at hadron colliders and includes - without any approximation - all partonic channels contributing to this process. This is the first complete fully differential calculation in NNLO QCD of a two-to-two scattering process with all coloured partons.Comment: 6 pages, 4 figures. Published journal version: title extended and few clarifications adde

Bump-hunting in LHC ttbar events

We demonstrate that a purposefully normalised NNLO top pair invariant mass differential spectrum can have very small theoretical uncertainty and, in particular, a small sensitivity to the top quark mass. Such observable can thus be a very effective bump-hunting tool for resonances decaying to top pair events during LHC Run II and beyond. To illustrate how the approach works, we concentrate on one specific example of current interest, namely, the possible 750 GeV di-gamma excess resonance Phi. Considering only theoretical uncertainties, we demonstrate that it is possible to distinguish pp -> Phi -> tt signals studied in the recent literature [Hespel, Maltoni and Vryonidou, arXiv:1606.04149] from the pure SM background with very high significance. Alternatively, in case of non-observation, a strong upper limit on the decay rate Phi -> tt can be placed.Comment: 8 pages, 6 figures, analytic fits attached, plot on top-mass sensitivity for the invariant mass distribution added, appendix on top-mass sensitivity of differential distributions added, minor additional changes and comments, matches published versio

Summary of the Topical Workshop on Top Quark Differential Distributions 2014

We summarise the Topical Workshop on Top Quark Differential Distributions 2014, which took place in Cannes immediately before the annual Top2014 conference. The workshop was motivated by the availability of top quark differential distributions at NNLO and the forthcoming LHC 13 TeV data. The main goal of the workshop was to explore the impact of improved calculations of top quark production on precision LHC measurements, PDF determinations and searches for physics beyond the Standard Model, as well as finding ways in which the high precision data from ATLAS, CMS and LHCb can be used to further refine theoretical predictions for top production.Comment: 9 pages, 5 figures, proceedings of TOP2014, 7th International Workshop on Top-Quark Physics, Cannes, Franc

Sector-improved residue subtraction: Improvements and Applications

We discuss two recent developments of the sector-improved residue subtraction scheme for handling real radiation at NNLO in QCD. We present a new phase space construction which minimizes the number phase space configurations for subtraction terms and we rederive the four-dimensional formulation of the scheme.Comment: Contribution to the proceedings of the Loops and Legs 2018 conference, St. Goar, German

Further exploration of top pair hadroproduction at NNLO

Top quark pair production is one of the cornerstones of the physics program at hadron colliders. In this contribution, we further explore the phenomenological implications of the recent NNLO calculation of the total inclusive cross-section. We provide a comparison of the scale dependence of the top pair hadroproduction cross section at different perturbative orders and study its perturbative convergence (with and without soft-gluon resummation). We also sketch how the NNLO top quark cross-section could be used to improve searches of physics beyond the Standard Model.Comment: 8 pages, 8 figures. Contribution to the proceedings of the twenty-seventh workshop "Les Rencontres de Physique de la Vall\'ee d'Aoste", held 24 Feb.-02 Mar. 2013 in La Thuile, Aosta Valley, Ital