Perturbative QCD effects and the search for a H->WW->l nu l nu signal at the Tevatron

TL;DR

This paper analyzes the effects of perturbative QCD on Higgs to WW signal detection at the Tevatron, comparing various computational tools and their impact on event acceptance and kinematic distributions.

Contribution

It provides a detailed comparison of NNLO QCD calculations with event generators like PYTHIA, HERWIG, and MC@NLO for Higgs production and decay channels.

Findings

NNLO QCD results differ from lower-order calculations and event generators.

Artificial Neural Network outputs are consistent across different tools.

PYTHIA underestimates acceptance compared to NNLO, HERWIG, and MC@NLO.

Abstract

The Tevatron experiments have recently excluded a Standard Model Higgs boson in the mass range 160 - 170 GeV at the 95% confidence level. This result is based on sophisticated analyses designed to maximize the ratio of signal and background cross-sections. In this paper we study the production of a Higgs boson of mass 160 GeV in the gg -> H -> WW -> l nu l nu channel. We choose a set of cuts like those adopted in the experimental analysis and compare kinematical distributions of the final state leptons computed in NNLO QCD to lower-order calculations and to those obtained with the event generators PYTHIA, HERWIG and MC@NLO. We also show that the distribution of the output from an Artificial Neural Network obtained with the different tools does not show significant differences. However, the final acceptance computed with PYTHIA is smaller than those obtained at NNLO and with HERWIG and MC@NLO. We also investigate the impact of the underlying event and hadronization on our results.