T $ \bar{\mathrm{t}} $ W± + t $ \bar{\mathrm{t}} $ Z hadroproduction at NLO accuracy in QCD with Parton Shower and Hadronization effects

M V Garzelli,Z Trócsányi,C G Papadopoulos,A Kardos

doi:10.1007/jhep11(2012)056

Abstract

Abstract We present theoretical predictions for the hadroproduction of t $ \bar{\mathrm{t}} $ W+, t $ \bar{\mathrm{t}} $ W− and t $ \bar{\mathrm{t}} $ Z at LHC as obtained by matching numerical computations at NLO accuracy in QCD with Shower Monte Carlo programs. The calculation is performed by PowHel, relying on the POWHEG-BOX framework, that allows for the matching between the fixed order computation, with input of matrix elements produced by the HELAC-NLO collection of event generators, and the Parton Shower evolution, followed by hadronization and hadron decays as described by PYTHIA and HERWIG. We focus on the dilepton and trilepton decay channels, studied recently by the CMS Collaboration.

Highlights

JHEP11(2012)056 for other processes at the same accuracy, which can be considered a good test of its robustness [7,8,9,10]
The calculation is performed by PowHel, relying on the POWHEG-BOX framework, that allows for the matching between the fixed order computation, with input of matrix elements produced by the HELAC-NLO collection of event generators, and the Parton Shower evolution, followed by hadronization and hadron decays as described by PYTHIA and HERWIG
This paper is new with respect to our previous ones, since here for the first time we produce predictions for tt W ± hadroproduction, and we concentrate on theleptonic decay channels of tt Z, the same channels that are nowadays preferred by the experimental collaborations, as much cleaner signals can be obtained with respect to the fully hadronic decay one

Summary

Introduction

JHEP11(2012) for other processes (tt, tt j, tt H/A) at the same accuracy, which can be considered a good test of its robustness [7,8,9,10]. While details on the implementation of tt Z in this framework were recorded in our previous papers [11, 12], the following ingredients, needed by POWHEG-BOX, were provided in case of tt W ± hadroproduction:. The phase space corresponding to three massive particles in the final state was provided in full analogy with our previous computations of the tt Z and tt H processes at the same accuracy [8, 12]

Objectives

Results

Conclusion