Subleading EW corrections and spin-correlation effects in $$t\bar{t}W$$ t
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Regular Article - Theoretical Physics
Subleading EW corrections and spin-correlation effects in t t¯W multi-lepton signatures Rikkert Frederixa , Ioannis Tsinikosb Theoretical Particle Physics, Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, 223 62 Lund, Sweden
Received: 2 June 2020 / Accepted: 22 August 2020 / Published online: 1 September 2020 © The Author(s) 2020
Abstract Recently a slight tension between data and predictions has been reported in t t¯W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to t t¯W production at the LHC. We find that this effect changes the t t¯W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.
1 Introduction With the 13 TeV LHC run, both ATLAS and CMS collaborations have measured the t t¯V (V = Z , W ) cross sections. These processes are studied either independently [1,2] or as irreducible backgrounds to t t¯ H (multilepton) searches [3,4]. In both cases a slight tension between theoretical predictions and data is observed for t t¯W production, with the data suggesting a somewhat larger cross section than Standard Model predictions. This slight tension between Standard Model predictions and data warrants further study of this process from both the experimental and the theoretical sides. At the production level the t t¯W process has recently been studied in detail at the complete-NLO accuracy [5]. In this work it was pointed out that the subleading EW corrections result in a ∼10% increase of the total cross section. This large contribution is due to the opening of t W → t W scattering diagrams, which are also studied in detail in [6] within a BSM context. The complete-NLO calculation has been matched a e-mail:
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to soft (threshold) gluon resummation, resulting in the mostaccurate predictions for the t t¯W production at the LHC to date [7,8]. Both these works have shown that t t¯W , in contrast to t t¯ Z and t t¯ H , does not become less sensitive to the scale choices even when including the resummation at NNLL accuracy. In other words, including the all-order soft-gluon resummation does not significantly decrease the theoretical uncertainties. This can predominantly be attributed to the absence of gluon-induced channels at LO; the latter only appear at higher orders and give sizeable contributions to the cross section. Since they do not contribute at LO they are not considered in the resummation frameworks of Refs. [7,8]. Incidentally, since the gg channels on
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