CDF Logo CDF Search for Higgs to WW* Production using a Combined Matrix Element and Neural Network Technique
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Abstract:

We report a search for standard model (SM) Higgs boson to WW* production in the two charged lepton (e, mu) and two neutrino final state in p-pbar collisions at sqrt(s) = 1.96 TeV. The data were collected with the CDF II detector at the Tevatron collider at Fermilab and correspond to an integrated luminosity of roughly 4.8 fb-1. In order to maximize sensitivity, three neural networks are separately trained to distinguish signal from background processes in final states with either zero, one, or two or more jets. For 0-jet events, likelihood ratios based on Matrix Element calculations are used as additional inputs to the neural network to further strengthen its discriminating power. In order to take advantage of the full signal acceptance, we also consider associated production with a W or Z boson and Higgs boson production via vector boson fusion for final states with one or more jets. Additional signal acceptance is gained by including events with low dilepton invariant mass as a separate search region. We also search for associated Higgs production in events with same sign dileptons in the final state. In the opposite sign event sample we observe (summing over all jet multiplicities) a total of 1567 candidate events compared against an expectation of 1550 ± 130 background events and 27 ± 5 signal events for a SM Higgs boson with a mass of 165 GeV/c2. In the low dilepton invariant mass sample we observe 85 candidate events compared against an expectation of 81 ± 7 background events and 0.8 ± 0.1 signal events for a SM Higgs boson with a mass of 165 GeV/c2. In the same sign event sample we additionally observe 81 candidate events compared with an expectation of 76 ± 13 background events and 1.9 ± 0.2 signal events for a SM Higgs boson with a mass of 165 GeV/c2. Based on these samples, we determine an observed 95% C.L. upper cross section limit of 1.2 times the SM prediction at NNLL for a Higgs mass of 165 GeV/c2 to be compared with the value for the median of the expected limit (1.2). Results for thirteen other Higgs mass hypotheses ranging from 110 GeV/c2 to 200 GeV/c2 are also presented.

 

Supporting Documents:

  • The results were first presented at Lepton-Photon 2009
  • More details are provided in the public note
  • Previous multivariate result with 4.8 fb-1: html
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    General Remarks:

  • The preliminary results were blessed in the Higgs group on August 14, 2009
  • Please contact us if you have any questions about including these results in a presentation
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     Updated by Eric James
    For problems or questions regarding this website contact jameseb_AT_fnal.gov
    Last updated: August 14 2009.