Search for the standard model Higgs boson produced in association with a top-quark pair in pp collisions at the LHC

TL;DR

This paper reports a search for the standard model Higgs boson produced with top-quark pairs at the LHC, setting limits on production cross sections using neural networks to distinguish signal from background.

Contribution

It introduces a novel analysis combining 7 TeV and 8 TeV data with neural network techniques to improve Higgs boson search sensitivity in top-quark pair events.

Findings

Observed limit is 5.8 times the SM expectation at 125 GeV.

Used neural networks for signal-background discrimination.

Combined data from two energy runs for enhanced sensitivity.

Abstract

A search for the standard model Higgs boson produced in association with a top-quark pair is presented using data samples corresponding to an integrated luminosity of 5.0 inverse femtobarns (5.1 inverse femtobarns) collected in pp collisions at the center-of-mass energy of 7 TeV (8 TeV). Events are considered where the top-quark pair decays to either one lepton+jets (t tbar to ell nu q q' b bbar) or dileptons (t tbar to ell(+) nu ell(-) nu b bbar), ell being an electron or a muon. The search is optimized for the decay mode H to b bbar. The largest background to the t tbar H signal is top-quark pair production with additional jets. Artificial neural networks are used to discriminate between signal and background events. Combining the results from the 7 TeV and 8 TeV samples, the observed (expected) limit on the cross section for Higgs boson production in association with top-quark pairs for a Higgs boson mass of 125 GeV is 5.8 (5.2) times the standard model expectation.