A Search For The Higgs Boson Using Neural Networks In Events With Missing Energy And Boldit B Quark Jets In P Bar P Collisions At Sqrt S

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A Search For The Higgs Boson Using Neural Networks In Events With Missing Energy And Boldit B Quark Jets In P Bar P Collisions At Sqrt S

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Author :
language : en
Publisher:
Release Date : 2009

A Search For The Higgs Boson Using Neural Networks In Events With Missing Energy And Boldit B Quark Jets In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.

We report on a search for the standard model Higgs boson produced in association with a W or Z boson in p{bar p} collisions at (square root)s = 1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb−1. We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a b hadron. We find good agreement between data and predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 150 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 6.9 (5.6) times the standard model prediction.

Search For The Higgs Boson In Events With Missing Transverse Energy And B Quark Jets Produced In Proton Antiproton Collisions At S

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language : en
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Release Date : 2008

Search For The Higgs Boson In Events With Missing Transverse Energy And B Quark Jets Produced In Proton Antiproton Collisions At S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ≈1 fb−1 integrated luminosity of p{bar p} collisions at √s = 1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 ± 43 (14.4 ± 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.

Search For The Higgs Boson In Events With Missing Transverse Energy And B Quark Jets Produced In Proton Antiproton Collisions At S 1 2

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Author :
language : en
Publisher:
Release Date : 2008

Search For The Higgs Boson In Events With Missing Transverse Energy And B Quark Jets Produced In Proton Antiproton Collisions At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

We search for the standard model Higgs boson produced in association with an electroweak vector boson in events with no identified charged leptons, large imbalance in transverse momentum, and two jets where at least one contains a secondary vertex consistent with the decay of b hadrons. We use ≈1 fb−1 integrated luminosity of p{bar p} collisions at √s = 1.96 TeV recorded by the CDF II experiment at the Tevatron. We find 268 (16) single (double) b-tagged candidate events, where 248 ± 43 (14.4 ± 2.7) are expected from standard model background processes. We place 95% confidence level upper limits on the Higgs boson production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model prediction.

Search For A Very Light Cp Odd Higgs Boson In Top Quark Decays From P P Collisions At 1 96 Tev

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language : en
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Release Date : 2011

Search For A Very Light Cp Odd Higgs Boson In Top Quark Decays From P P Collisions At 1 96 Tev written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.

We present the results of a search for a very light CP-odd Higgs boson a1° originating from top quark decays t → H{sup {+-}}b → W{sup {+-}(*)} a1° b, and subsequently decaying into??−. Using a data sample corresponding to an integrated luminosity of 2.7 fb−1 collected by the CDF II detector in p{bar p} collisions at 1.96 TeV, we perform a search for events containing a lepton, three or more jets, and an additional isolated track with transverse momentum in the range 3 to 20 GeV/c. Observed events are consistent with background sources, and 95% C.L. limits are set on the branching ratio of t → H{sup {+-}}b for various masses of H{sup {+-}} and a1°.

Search For Neutral Higgs Bosons In The Multi B Jet Topology In 5 2fb 1 Of P Bar P Collisions At Sqrt S

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language : en
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Release Date : 2010

Search For Neutral Higgs Bosons In The Multi B Jet Topology In 5 2fb 1 Of P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb−1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.

Search For A Light Higgs Boson In The Channel Wh U2192 E E B Bar B In P Bar P Collision With Sqrt S

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language : en
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Release Date : 2005

Search For A Light Higgs Boson In The Channel Wh U2192 E E B Bar B In P Bar P Collision With Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.

Although the standard model of particle physics has been very successfull in describing nature it needs to be extended by the Higgs mechanism to explain the particle masses observed in experiments. This mechanism introduces a new elementary particle called the Higgs boson. Current research at particle accelerators focuses on the search for the Higgs boson as a major goal. This analysis uses the data recorded with the D0-detector of the Tevatron at the Fermi National Accelerator Laboratory (FNAL). The Tevatron collides protons and antiprotons at a center of mass energy of √s=1.96 TeV. The primary goal of the analysis was the search for a light Higgs boson in the WH channel. For this the process pp→ WH → ev bb was used. Furthermore a measurement of the Wbb production cross section has been performed. For the measurements a total intagrated luminosity of L=255pb-1 was available. For the selection of the desired processes events with electrons, missing transverse momentum and at least two jets have been used. At least two of the jets were required to be identified as b-jets. To obtain an efficient event selection many event properties had to be calculated and methods to cut on them needed to be optimized. Based on the selected events the Wbb production cross section has been calculated. After includinng the branching ratio BR(W→ev)=0.108 the result is ?(Wbb)=21.8 pb (+15.5; -20.0 pb(sys+stat)) for events where the b-quarks satisfy p_T>8 GeV und.

Search For The Higgs Boson Produced With Z To Ell Ell In P Bar P Collisions At Sqrt S

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language : en
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Release Date : 2008

Search For The Higgs Boson Produced With Z To Ell Ell In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

The authors present a search for the Higgs boson in the process q{bar q} → ZN → l+l− b{bar b}. The analysis uses an integrated luminosity of 1 fb−1 of p{bar p} collisions produced at √s = 1.96 TeV and accumulated by the upgraded Collider Detector at Fermilab (CDF II). They employ artificial neural networks both to correct jets mismeasured in the calorimeter, and to distinguish the signal kinematic distributions from those of the background. They see no evidence for Higgs boson production, and set 95% CL upper limits on [sigma]{sub ZH} · [Beta](H → b{bar b}), ranging from 1.5 pb to 1.2 pb for a Higgs mass (m{sub H}) of 110 to 150 GeV/c2.

Search For A Higgs Boson In The Decay Channel H To Zz To Q Qbar Ell L In Pp Collisions At Sqrt S

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language : en
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Release Date : 2012

Search For A Higgs Boson In The Decay Channel H To Zz To Q Qbar Ell L In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.

A search for the standard model Higgs boson decaying into two Z bosons with subsequent decay into a final state containing two quark jets and two leptons, H to ZZ(*) to q q-bar l-l+ is presented. Results are based on data corresponding to an integrated luminosity of 4.6 inverse femtobarns of proton-proton collisions at sqrt(s)=7 TeV, collected with the CMS detector at the LHC. In order to discriminate between signal and background events, kinematic and topological quantities, including the angular spin correlations of the decay products, are employed. Events are further classified according to the probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for the Higgs boson is found, and upper limits on its production cross section are determined for a Higgs boson of mass between 130 and 600 GeV.

Search For Neutral Higgs Bosons In Multi B Jet Events In P Bar P Collisions At Sqrt S

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Author :
language : en
Publisher:
Release Date : 2008

Search For Neutral Higgs Bosons In Multi B Jet Events In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

Search For Higgs Boson Production In Proton Antiproton Collisions At U221a S

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language : en
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Release Date : 2006

Search For Higgs Boson Production In Proton Antiproton Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.

We performed a search for Standard Model Higgs boson production in association with W boson (p$ar{p}$ → W±H → lvb$ar{b}$) in p$ar{p}$ collisions at √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-1. The experimental final state of WH → lvb$ar{b}$ process is lepton (e±/?±), 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 pT 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 ?(p$ar{p}$ → WH) • Br(H → b$ar{b}$) as 3.9 to 1.3 for Higgs boson mass from 110 to 150 GeV/c2 at 95% confidence level (C.L.). The upper limit obtained from WH → lvb$ar{b}$ process with 1 fb-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 → ?$ar{v}$b$ar{b}$, ZH → l$ar{ℓ}$b$ar{b}$ and gg → H → W+W- → l$ar{ℓ}$v$ar{v}$ 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 ((? • Br)95/(? • Br)SM), which results in the ratio as 10 to 40 for Higgs boson mass between 110 and 200 GeV/c2. Finally, the combination of Higgs boson searches between CDF and D0 is also performed. The resulting constraint on (? • Br)95/(? • Br)SM is about 4 to 10 for Higgs boson mass between 110 and 200 GeV/c2.