Abstract

This paper presents a search for standard model Higgs boson production in association with a $W$ boson using events recorded by the CDF experiment in a dataset corresponding to an integrated luminosity of 5.6 fb-1. The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on the Higgs boson production rate. The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between 100 and 150 GeV. The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.

Highlights

  • In the standard model (SM), the Higgs mechanism [1,2,3] is responsible for the spontaneous breaking of the SU(2) x U(1) gauge symmetry which generates the masses of the gauge bosons and more indirectly allows for the fermion masses

  • For the analyses presented in this article, muons are detected in four separate subdetectors

  • CEM, PHX, CMUP, and central muon extension (CMX) leptons are commonly known as tight leptons and the muons collected by the energy of the jet (ET) vector (E/ T) + jets trigger are known as extended muon coverage (EMC) muons

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Summary

INTRODUCTION

At the Tevatron ppcollider, the Higgs boson is expected to be produced mainly by gluon fusion, while the Lubbock, TX 79609, USA, ccUniversidad Tecnica Federico Santa Maria, 110v Valparaiso, Chile, ddYarmouk University, Irbid 211-63, Jordan, most frequent production channel is the associated production of Higgs and W bosons, W H. To distinguish signal from background events a matrix element technique [14, 15] is applied, in which event probability densities for the signal and background hypotheses are calculated and used to create a powerful discriminator This method was used as part of the observation of single top production [16] and many other analyses within the CDF collaboration, such as the measurement of the W W + W Z cross section [17], the measurement of the top quark mass [18], the search for SM Higgs boson production in the W W decay channel [19], and the measurement of the W W production cross section [20].

THE CDF II DETECTOR
DATA SAMPLE AND EVENT RECONSTRUCTION
Electron identification
Muon identification
Lepton identification efficiencies
Jet reconstruction and corrections
Secondary Vertex Tagger
Jet Probability Tagger
Tagging efficiencies and mistag rates
Splitting tagging categories
SIGNAL MODELING AND ACCEPTANCE
BACKGROUND
Monte-Carlo based background processes
Non-W multijet events
Rates of events with mistagged jets
Summary of background estimation
Validation of the background model
VIII. MATRIX ELEMENT METHOD
Event probability
Transfer functions
X X gluons
Event probability discriminant
Validation of the discriminant output
SYSTEMATIC UNCERTAINTIES
RESULTS
CONCLUSIONS
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