NLO QCD+EW predictions for tHj and tZj production at the LHC
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Springer
Received: June 25, 2020 Accepted: July 24, 2020 Published: August 19, 2020
Davide Pagani,a Ioannis Tsinikosb and Eleni Vryonidouc a
Theory Group, DESY, Notkestrasse 85, 22607 Hamburg, Germany b Theoretical Particle Physics, Department of Astronomy and Theoretical Physics, Lund University, S¨ olvegatan 14A, SE-223 62 Lund, Sweden c Theoretical Physics Department, CERN, CH-1211 Geneva 23, Switzerland
E-mail: [email protected], [email protected], [email protected] Abstract: In this work we calculate the cross sections for the hadroproduction of a single top quark or antiquark in association with a Higgs (tHj) or Z boson (tZj) at NLO QCD+EW accuracy. In the case of tZj production we consider both the case of the Z boson undecayed and the complete final state t`+ `− j, including off-shell and non-resonant effects. We perform our calculation in the five-flavour-scheme (5FS), without selecting any specific production channel (s-, t- or tW associated). Moreover, we provide a more realistic estimate of the theory uncertainty by carefully including the differences between the fourflavour-scheme (4FS) and 5FS predictions. The difficulties underlying this procedure in the presence of EW corrections are discussed in detail. We find that NLO EW corrections are in general within the NLO QCD theory uncertainties only if the flavour scheme uncertainty (4FS vs. 5FS) is taken into account. For the case of t`+ `− j production we also investigate differences between NLO QCD+EW predictions and NLO QCD predictions matched with a parton shower simulation including multiple photon emissions. Keywords: NLO Computations, QCD Phenomenology ArXiv ePrint: 2006.10086
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP08(2020)082
JHEP08(2020)082
NLO QCD+EW predictions for tHj and tZj production at the LHC
Contents 1 Introduction
1
2 Calculation setup 2.1 Flavour-scheme and scale uncertainties 2.2 Separation of different production modes 2.3 Input parameters
3 4 6 9 11 12 12 13 16 16 18 23
4 Conclusions
26
1
Introduction
The study of the interactions of the top quark, gauge and Higgs bosons is one of the main goals of TeV-scale colliders. After the discovery of the Higgs boson in the Run I, the Large Hadron Collider (LHC) has reached a golden era of precision physics and will continue to stress-test the predictions of the Standard Model (SM) of elementary particles. The success of this ambitious research program critically depends on a collaborative theoretical and experimental effort to detect deviations and/or constrain new physics, with sensitivities that reach the multi-TeV scale. The LHC has opened new possibilities, allowing for the first time the measurement of processes that directly probe the interaction of the top quark with both the neutral gauge bosons and the Higgs boson. This set of processes consists of the associated production of a single top or a top-quark pair with a Higgs or a neutral gauge boson. Since these processes probe some of the least known i
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