Electroweak tt¯ hadroproduction in the presence of heavy Z′ and W′ bosons at NLO QCD in POWHEG

Mohammad Mahdi Altakach,Tomáš Ježo,Michael Klasen,Ingo Schienbein,Jean-Nicolas Lang

doi:10.1103/physrevd.103.115026

Abstract

We extend and improve upon our previous calculation of electroweak top-quark pair hadroproduction in extensions of the Standard Model with extra heavy neutral and charged spin-1 resonances. In particular, we allow for flavour-non-diagonal $Z'$ couplings and take into account non-resonant production in the SM and beyond including the contributions with $t$-channel $W$ and $W'$ bosons. All amplitudes are generated using the Recola2 package. As in our previous work, we include NLO QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interference effects between SM and new physics amplitudes. We consider the Sequential Standard Model, the Topcolour model, as well as the Third Family Hypercharge Model featuring non-flavour-diagonal $Z'$ couplings which has been proposed recently to explain the anomalies in $B$ decays. We present numerical results for $t \bar t$ cross sections at hadron colliders with a centre-of-mass energy up to 100 TeV.

Highlights

The Standard Model (SM) of particle physics, based on an SUð3ÞC × SUð2ÞL × Uð1ÞY gauge symmetry, is an extremely successful theory that accounts for a wide range of experimental measurements at both the intensity and energy frontiers
It is in the spirit of the second approach, hypothesis testing,6 that we use our next-to-leading order calculation to obtain predictions for top-quark–pair production for the three models introduced in the preceding section: the sequential Standard Model, the topcolor model, and the third family hypercharge model
We extended and improved upon our previous calculation of electroweak top-quark pair hadroproduction in extensions of the Standard Model with extra heavy neutral and charged spin-1 resonances

Summary

Introduction

The Standard Model (SM) of particle physics, based on an SUð3ÞC × SUð2ÞL × Uð1ÞY gauge symmetry, is an extremely successful theory that accounts for a wide range of experimental measurements at both the intensity and energy frontiers. It is widely believed to be incomplete for different reasons. The SM does not include gravity, it does not provide a candidate for a cold dark matter particle, the CP-violating phase of the SM CKM (Cabibbo-Kobayashi-Maskawa) matrix is not sufficient to explain the matter-antimatter asymmetry observed in the Universe, and massive neutrinos are, a priori, not accounted for in the SM.

Objectives

Results

Conclusion