Search for Higgs boson production in proton-antiproton collisions at s**(1/2) = 1.96 TeV

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We performed a search for Standard Model Higgs boson production in association with W boson (p{bar p} {yields} W{sup {+-}}H {yields} {ell}{nu}b{bar b}) in p{bar p} collisions at {radical}s = 1.96 TeV. The search uses the data collected between February 2002 and February 2006 at Collider Detector at Fermilab (CDF), which corresponds to an integrated luminosity of about 1 fb{sup -1}. The experimental final state of WH {yields} {ell}{nu}b{bar b} process is lepton (e{sup {+-}}/{mu}{sup {+-}}), missing transverse energy and two jets. The largest background in lepton+jets events is W+light flavor process, therefore the identification of jets as b-jets reduces ... continued below

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139 pages

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Kusakabe, Yoshiaki & U., /Waseda December 1, 2006.

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We performed a search for Standard Model Higgs boson production in association with W boson (p{bar p} {yields} W{sup {+-}}H {yields} {ell}{nu}b{bar b}) in p{bar p} collisions at {radical}s = 1.96 TeV. The search uses the data collected between February 2002 and February 2006 at Collider Detector at Fermilab (CDF), which corresponds to an integrated luminosity of about 1 fb{sup -1}. The experimental final state of WH {yields} {ell}{nu}b{bar b} process is lepton (e{sup {+-}}/{mu}{sup {+-}}), missing transverse energy and two jets. The largest background in lepton+jets events is W+light flavor process, therefore the identification of jets as b-jets reduces this kind of background significantly. We used displaced SECondary VerTeX b-tagging (SECVTX) technique, which utilizes the signature that b-jets have secondary vertex displaced away from primary vertex because of the long life time of B-mesons. However, there is still much contamination in SECVTX b-tagged jets. Finite resolution of secondary vertex tracking measurements results in false tags, and c-jets are also identified as b-jets due to the long life time of D-mesons frequently. For the purpose of increasing the purity of the SECVTX b-tagged jets, we applied Neural Network to SECVTX tagged jets for the first time by using secondary vertex variables and some variables independent of it. Neural Network filter rejects 65% of light flavor jets and 50% of c-jets from the SECVTX tagged jets. We improved the sensitivity of the Higgs boson signal search by 10% with Neural Network b-tagging technique. Events with one high p{sub T} electron or muon, large missing transverse energy and either single SECVTX b-tagged jet which passes the Neural Network filter or at least two SECVTX b-tagged jets are selected. The number of selected events and dijet mass distributions are consistent with the Standard Model background expectations. Therefore we set an upper limit on {sigma}(p{bar p} {yields} WH) {center_dot} Br(H {yields} b{bar b}) as 3.9 to 1.3 for Higgs boson mass from 110 to 150 GeV/c{sup 2} at 95% confidence level (C.L.). The upper limit obtained from WH {yields} {ell}{nu}b{bar b} process with 1 fb{sup -1} is far away from the Standard Model Higgs boson production expectation by a factor of 20 to 100 as a function of Higgs boson mass. To obtain stronger constraint on the Higgs boson production, we combined the upper limits obtained in processes of ZH {yields} {nu}{bar {nu}}b{bar b}, ZH {yields} {ell}{bar {ell}}b{bar b} and gg {yields} H {yields} W{sup +}W{sup -} {yields} {ell}{bar {ell}}{nu}{bar {nu}} at CDF. The combination of different channels gives a constraint on the ratio of 95% confidence level upper limit divided by the Standard Model prediction (({sigma} {center_dot} Br){sub 95}/({sigma} {center_dot} Br){sub SM}), which results in the ratio as 10 to 40 for Higgs boson mass between 110 and 200 GeV/c{sup 2}. Finally, the combination of Higgs boson searches between CDF and D0 is also performed. The resulting constraint on ({sigma} {center_dot} Br){sub 95}/({sigma} {center_dot} Br){sub SM} is about 4 to 10 for Higgs boson mass between 110 and 200 GeV/c{sup 2}.

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139 pages

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  • Report No.: FERMILAB-THESIS-2006-64
  • Grant Number: AC02-07CH11359
  • DOI: 10.2172/935474 | External Link
  • Office of Scientific & Technical Information Report Number: 935474
  • Archival Resource Key: ark:/67531/metadc892960

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  • December 1, 2006

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  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 8, 2016, 10:06 p.m.

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Kusakabe, Yoshiaki & U., /Waseda. Search for Higgs boson production in proton-antiproton collisions at s**(1/2) = 1.96 TeV, thesis or dissertation, December 1, 2006; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc892960/: accessed July 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.