Search for Higgs Boson Production in Association with a W Boson in 1.96-TeV Proton - Antiproton Collisions

Abstract

We have searched for the Standard Model Higgs boson production in association with a W{sup {+-}} boson. This search is based on the data collected between February 2002 and May 2007, corresponding to an integrated luminosity of 1.9 fb{sup -1} collected by the Collider Detector at Fermilab (CDF) at the Tevatron which is a p{bar p} collider at a center of mass energy 1.96 TeV. W+Higgs channel is one of the most promising channels for the Higgs search at Tevatron in the low Higgs mass region (m{sub H} < 135 GeV/c{sup 2}), where Higgs boson decays into b{bar b} dominantly. The detection of lepton from the W boson decay makes the W+Higgs events much cleaner than the direct Higgs production events which have the largest production cross section. Experimentally we select events with a high p{sub T} lepton, high missing transverse energy and two b-quark jets. This signature is same as for the W+jets background which has a huge cross section. To reduce the W+jets background, b-jet identification algorithms are applied to at least one jet. The expected signal events in 1.9fb{sup -1} are 1.82 {+-} 0.15 and 1.68 {+-} 0.20 for one b-tagged events and two b-tagged events, respectively.more » The observed data is 805 for one b-tagged events and 173 for two b-tagged events. They are consistent with the Standard Model background expectation. After selecting the events, Neural Network (NN) discriminant technique is performed to distinguish the signal events from still residual backgrounds. We see no evidence for a Higgs signal in the dijet mass distribution and in the NN output distribution. We set a 95% confidence level upper limit on the W+Higgs production cross section times the branching ratio of the Higgs decaying into a b{bar b} pair. We obtained {sigma}(p{bar p} {yields} W{sup {+-}}H) x BR(H {yields} b{bar b}) < 1.4 to 0.9 pb for Higgs masses from 110 GeV/c{sup 2} to 150 GeV/c{sup 2} using the NN output distribution. The limits are about 10 times higher than the Standard Model expectation in the low Higgs mass region.« less