Simultaneous extraction of $α_s$ and $m_t$ from LHC $t\bar{t}$ differential distributions

Abstract

We present a joint extraction of the strong coupling α s and the top-quark pole mass m t from measurements of top-quark pair production performed by the ATLAS and CMS experiments at the 8 TeV LHC. For the first time, differential NNLO theory predictions for different values of the top-quark mass are utilised for four kinematic distributions: the average transverse momentum of the top-quark, its average rapidity and the pair invariant mass and rapidity. The use of fastNLO tables for these distributions allows rapid evaluation of the differential theory predictions for different PDF sets. We consider the single differential distributions from the experiments both separately and in combination in order to obtain the best fit to theory. Our final values are α s = 0.1159 +0.0013 −0.0014 and m t = 173.8 +0.8 −0.8 GeV which are compatible with previous extractions using top-quark measurements. In the case of m t , our value is also compatible with the world average value collated by the Particle Data Group.

Two-loop master integrals for a planar topology contributing to pp → $$ t\overline{t}j $$

“…where G ij ( v) = v i • v j is the Gram matrix and s ij = (p i + p j ) 2 . The square roots ∆ 5 and ∆ 6 appear in some intermediate steps of the differential equations reconstruction but they are not related to the normalisation of any master integral.…”

“…The stability of the SM vacuum is highly sensitive to the value of the top mass whose precision measurement is a high priority at the Large Hadron Collider (LHC). Top quark pair production at hadron colliders is known extremely precisely both theoretically and experimentally and can be used to constrain SM parameters and parton distribution functions [1,2]. It has been argued that top-quark pair production in association with a jet is even more sensitive to the value of the top quark mass [3][4][5], yet the theoretical predictions for this process are not currently at the same level of precision as the experimental measurements.…”

Zero-jettiness resummation for top-quark pair production at the LHC

“…[1][2][3][4][5][6][7][8][9][10][11]. Such measurements are important for extracting properties of the SM such as the strong coupling α s and the top-quark mass [12,13].…”

Precision physics with inclusive QCD processes

“…A very recent analysis of ̄ production data from ATLAS and CMS includes also NNLO predictions of the differential distributions [317]. Among the many extractions studied, using different data sets and PDFs, the most precise determination of the strong coupling is obtained from two ATLAS distributions and the CT14 PDF set, which give…”