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Search For The Higgs Boson And Rare Standard Model Processes In The Et B Jets Signature At The Collider Detector At Fermilab
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Book Synopsis Search for the Higgs Boson and Rare Standard Model Processes in the ET+B-Jets Signature at the Collider Detector at Fermilab by :
Download or read book Search for the Higgs Boson and Rare Standard Model Processes in the ET+B-Jets Signature at the Collider Detector at Fermilab written by and published by . This book was released on 2011 with total page 477 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study rare processes of the standard model of particle physics (SM) in events with missing transverse energy ET, no leptons, and two or three jets, of which at least one is identified as originating from a $b$-quark (ET+b-jets signature). We present a search for the SM Higgs boson produced in association with a $W$ or $Z$ boson when the Higgs decays into \bbbar. We consider the scenario where $Z \to \nu \nu$, or $W \to l \nu$ and the lepton escapes detection. This dissertation analyzes $7.8\̃mbox{fb${̂-1}$}$ of data collected by the CDFĨI experiment at Fermilab. For the first time, we analyze events with \emph{relaxed kinematic} requirements, yielding an increase of 30- 40\% in acceptance to the $WH/ZH$ signal. We collect events from three different triggers and parametrize the efficiency of their logical combination (OR) using a novel artificial neural network ($NN$) technique. To increase the sensitivity to the signal, we implement a $NN$ to remove the huge instrumental background. An additional $NN$ is used to discriminate the Higgs signal from the remaining background. We check our background modeling by comparing data against backgrounds in many control regions, and find good agreement. Observing no significant excess in the data, we place 95\% confidence level (C.L.) upper limits on the Higgs boson production cross section. For a mass of $115\̃mbox{GeV/$c2̂$}$ the expected (observed) limit is $2.9$ ($2.3$) times the standard model prediction. Compared to the last iteration of this analysis, this result improves the significance by 10\% throughout the $100-150\̃mbox{GeV/$c2̂$}$ mass range. This is one of the most sensitive at the Tevatron in this mass range. We cross-check the tools developed in this dissertation by measuring the cross-section of top pair, electroweak single top and diboson ($WZ+ZZ$) production.
Book Synopsis Search for the Higgs Boson and Rare Standard Model Processes in the \mbox{$\protect \raisebox{0.3ex}{$\not$}E_T$}+$b$-jets Signature at the Collider Detector at Fermilab by :
Download or read book Search for the Higgs Boson and Rare Standard Model Processes in the \mbox{$\protect \raisebox{0.3ex}{$\not$}E_T$}+$b$-jets Signature at the Collider Detector at Fermilab written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study rare processes of the standard model of particle physics (SM) in events with missing transverse energy (\mbox{$\protect\raisebox{0.3ex}{$\not$}E_T$}), no leptons, and two or three jets, of which at least one is identified as originating from a $b$-quark (\mbox{$\protect \raisebox{0.3ex}{$\not$}E_T$}+$b$-jets signature). We present a search for the SM Higgs boson produced in association with a $W$ or $Z$ boson when the Higgs decays into \bbbar. We consider the scenario where $Z \to \nu \nu$, or $W \to l \nu$ and the lepton escapes detection. This dissertation analyzes $7.8~\mbox{fb$^{-1}$}$ of data collected by the CDF~II experiment at Fermilab. For the first time, we analyze events with \emph{relaxed kinematic} requirements, yielding an increase of 30- 40\% in acceptance to the $WH/ZH$ signal. We collect events from three different triggers and parametrize the efficiency of their logical combination (OR) using a novel artificial neural network ($NN$) technique. To increase the sensitivity to the signal, we implement a $NN$ to remove the huge instrumental background. An additional $NN$ is used to discriminate the Higgs signal from the remaining background. We check our background modeling by comparing data against backgrounds in many control regions, and find good agreement. Observing no significant excess in the data, we place 95\% confidence level (C.L.) upper limits on the Higgs boson production cross section. For a mass of $115~\mbox{GeV/$c^2$}$ the expected (observed) limit is $2.9$ ($2.3$) times the standard model prediction. Compared to the last iteration of this analysis, this result improves the significance by 10\% throughout the $100-150~\mbox{GeV/$c^2$}$ mass range. This is one of the most sensitive at the Tevatron in this mass range. We cross-check the tools developed in this dissertation by measuring the cross-section of top pair, electroweak single top and diboson ($WZ+ZZ$) production.
Book Synopsis Search for the Standard Model Higgs Boson Produced in Association with a W Boson in the Isolated-track Charged-lepton Channel Using the Collider Detector at Fermilab by :
Download or read book Search for the Standard Model Higgs Boson Produced in Association with a W Boson in the Isolated-track Charged-lepton Channel Using the Collider Detector at Fermilab written by and published by . This book was released on 2011 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Higgs boson is the only elementary particle predicted by the Standard Model (SM) that has not yet been observed experimentally. If it exists, it explains the spontaneous electroweak symmetry breaking and the origin of mass for gauge bosons and fermions. We test the validity of the SM by performing a search for the associated production of a Higgs boson and a W boson in the channel where the Higgs boson decays to a bottom-antibottom quark pair and the W boson decays to a charged lepton and a neutrino (the WH channel). We study a dataset of proton-antiproton collisions at a centre-of-mass energy √s = 1.96 TeV provided by the Tevatron accelerator, corresponding to an integrated luminosity of 5.7 fb−1, and recorded using the Collider Detector at Fermilab (CDF).We select events consistent with the signature of exactly one charged lepton (electron or muon), missing transverse energy due to the undetected neutrino (MET) and two collimated streams of particles (jets), at least one of which is required to be identified as originating from a bottom quark. We improve the discrimination of Higgs signal from backgrounds through the use of an artificial neural network. Using a Bayesian statistical inference approach, we set for each hypothetical Higgs boson mass in the range 100-150 GeV/c2 with 5 GeV/c2 increments a 95% credibility level (CL) upper limit on the ratio between the Higgs production cross section times branching fraction and the SM prediction. Our main original contributions are the addition of a novel charged lepton reconstruction algorithm with looser requirements (ISOTRK) with respect the electron or muon tight criteria (TIGHT), as well as the introduction of a novel trigger-combination method that allows to maximize the event yield while avoiding trigger correlations and that is used for the ISOTRK category. The ISOTRK candidate is a high-transverse-momentum good-quality track isolated from other activity in the tracking system and not required to match a calorimeter cluster, as for a tight electron candidate, or an energy deposit in the muon detector, as for a tight muon candidate. The ISOTRK category recovers real charged leptons that otherwise would be lost in the non-instrumented regions of the detector. This allows the reconstruction of more W boson candidates, which in turn increases the number of reconstructed WH signal candidate events, and therefore improves the sensitivity of the WH search. For the TIGHT charged lepton categories, we employ charged-lepton-dedicated triggers to improve the rate of WH signal acceptance during data taking. Since there is no ISOTRK-dedicated trigger at CDF, for the ISOTRK charged lepton category we employ three MET-plus-jets-based triggers. For each trigger we first identify the jet selection where the trigger efficiency is flat with respect to jet information (transverse energy and direction of motion in the transverse plane for the two jets in the event) and then we parametrize the trigger efficiency as a function of trigger MET. On an event-by-event basis, for each trigger we compute a trigger efficiency as a function of trigger parametrization, trigger MET, jet information, trigger prescale and information about whether the trigger is defined or not. For the ISOTRK category we combine the three triggers using a novel method, which allows the combination of any number of triggers in order to maximize the event yield while avoiding trigger correlations. On an event-by-event basis, only the trigger with the largest efficiency is used. By avoiding a logical 'OR' between triggers, the loss in the yield of events accepted by the trigger combination is compensated by a smaller and easier-to-compute corresponding systematic uncertainty. The addition of the ISOTRK charged lepton category to the TIGHT category produces an increase of 33% in the WH signal yield and a decrease of 15.5% to 19.0% in the median expected 95% CL cross-section upper limits across the entire studied Higgs mass interval. The improvement in analysis sensitivity is smaller than the improvement in signal yield because the ISOTRK category has a smaller signal over background ratio than the TIGHT category, due to the looser ISOTRK reconstruction criteria. The observed (median expected) 95% CL SM Higgs upper limits on cross section times branching ratio vary between 2.39 x SM (2.73 x SM) for a Higgs mass of 100 GeV/c2 to 31.1 x SM (31.2 x SM) for a Higgs mass of 150 GeV/c2, while the value for a 115 GeV/c2 Higgs boson is that of 5.08 x SM (3.79 x SM). The novel trigger combination method is already in use by several CDF analyses. It is applicable to any analysis that uses triggers based on MET and jets, such as supersymmetry searches at the ATLAS and CMS experiments at the Large Hadron Collider. In its most general form, the method can be used by any analysis that combines any number of different triggers.
Book Synopsis From The Tevatron To The Lhc: Physics At Large Accelerators - Proceedings Of The Xxiv International Meeting On Fundamen by : Antonio Ferrer
Download or read book From The Tevatron To The Lhc: Physics At Large Accelerators - Proceedings Of The Xxiv International Meeting On Fundamen written by Antonio Ferrer and published by World Scientific. This book was released on 1997-07-15 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects a series of papers presented at the XXIV International Meeting on Fundamental Physics. This annual conference is devoted to reviewing current topics in the field of high energy physics. From the Tevatron to the LHC reviews the present status of experiments at large accelerators (Tevatron, LEP, LHC) and deals with selected subjects like CP violation, B physics, glueballs, neutrinos and supersymmetry.
Book Synopsis Particle Physics Reference Library by : Herwig Schopper
Download or read book Particle Physics Reference Library written by Herwig Schopper and published by Springer Nature. This book was released on 2020 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first open access volume of the handbook series contains articles on the standard model of particle physics, both from the theoretical and experimental perspective. It also covers related topics, such as heavy-ion physics, neutrino physics and searches for new physics beyond the standard model. A joint CERN-Springer initiative, the "Particle Physics Reference Library" provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A, B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access
Book Synopsis The God Particle by : Leon M. Lederman
Download or read book The God Particle written by Leon M. Lederman and published by Houghton Mifflin Harcourt. This book was released on 2006 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: A fascinating tour of particle physics from Nobel Prize winner Leon Lederman. At the root of particle physics is an invincible sense of curiosity. Leon Lederman embraces this spirit of inquiry as he moves from the Greeks' earliest scientific observations to Einstein and beyond to chart this unique arm of scientific study. His survey concludes with the Higgs boson, nicknamed the God Particle, which scientists hypothesize will help unlock the last secrets of the subatomic universe, quarks and all--it's the dogged pursuit of this almost mystical entity that inspires Lederman's witty and accessible history.
Book Synopsis Search for Higgs Boson Production in Proton-antiproton Collisions at {u221A}s by :
Download or read book Search for Higgs Boson Production in Proton-antiproton Collisions at {u221A}s written by and published by . This book was released on 2006 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book High Energy Physics Index written by and published by . This book was released on 1990 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis D0 Search for the Higgs Boson in Multijet Events by : Alex Melnitchouk
Download or read book D0 Search for the Higgs Boson in Multijet Events written by Alex Melnitchouk and published by . This book was released on 2006 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present two searches for the Higgs boson in {radical}s = 1.96 TeV p{bar p} collisions using data taken with the D0 detector during Run II of the Fermilab Tevatron collider. The first study is a search for neutral Higgs bosons produced in association with bottom quarks. The cross sections for these processes are enhanced in many extensions of the standard model (SM), such as in its minimal supersymmetric extension at large tan {beta}. The results of our analysis agree with expectations from the SM, and we use our measurements to set upper limits on the production of neutral Higgs bosons in the mass range of 90 to 150 GeV. The second study is a search for the standard model Higgs boson produced in association with the Z boson. We study the p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b} channel, which is one of the most sensitive ways to search for light Higgs bosons at the Tevatron. We select multijet events with large imbalance in transverse momentum and two b-tagged jets. Then we search for a peak in invariant mass distribution of two b-tagged jets. After subtracting the backgrounds, we set the 95% C.L. upper limits on the {sigma}(p{bar p} {yields} ZH {yields} {nu}{bar {nu}}) x BR(H {yields} b{bar b}) for Higgs masses between 105 and 135 GeV.
Book Synopsis Discovery Of The Higgs Boson by : Aleandro Nisati
Download or read book Discovery Of The Higgs Boson written by Aleandro Nisati and published by World Scientific. This book was released on 2016-08-26 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis Search for the Higgs Boson in Lepton, Tau, and Jets Final States by :
Download or read book Search for the Higgs Boson in Lepton, Tau, and Jets Final States written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with two or more jets using 9.7 fb-1 of Run II Fermilab Tevatron Collider data collected with the D0 detector. The analysis is sensitive to Higgs boson production via gluon fusion, associated vector boson production, and vector boson fusion, followed by the Higgs boson decay to tau lepton pairs or to W boson pairs. The ratios of 95% C.L. upper limits on the cross section times branching ratio to those predicted by the standard model are obtained for orthogonal subsamples that are enriched in either H → [tau] [tau] decays or H → WW decays, and for the combination of these subsample limits. The observed and expected limit ratios for the combined subsamples at a Higgs boson mass of 125 GeV are 11.3 and 9.0 respectively.
Book Synopsis Search for the Standard Model Higgs Boson in Z H ---] Nu Anti-nu B Anti-b Channel at by :
Download or read book Search for the Standard Model Higgs Boson in Z H ---] Nu Anti-nu B Anti-b Channel at written by and published by . This book was released on 2009 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for a low mass Standard Model Higgs boson produced in association with a Z boson decaying invisibly into a pair of neutrinos at a center-of-mass energy of √s = 1.96 TeV with the D0 detector at the Fermilab Tevatron collider. The final state is characterized by the presence of two b-tagged jets from the Higgs boson decay and a large imbalance in the transverse energy of the event. This channel is very powerful because of the large Z → [nu]{anti {nu}} branching ratio, but also has many experimental challenges due to the large multijet background and the absence of visible carged leptons in the final state. We present the result with 5.2 fb−1 of data and discuss the recent improvements in the sensitivity.
Book Synopsis A Search for the Higgs Boson in the Zh Channel with the D0 Detector at the Fermilab Tevatron Collider by : James Matthew Heinmiller
Download or read book A Search for the Higgs Boson in the Zh Channel with the D0 Detector at the Fermilab Tevatron Collider written by James Matthew Heinmiller and published by . This book was released on 2006 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: This analysis describes a search for a standard model Higgs boson produced in association with a Z boson through the decay mode ZH {yields} e{sup +}e{sup -}b{bar b} in p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron Collider. The data sample used in this analysis corresponds to 452 pb{sup -1} of integrated luminosity accumulated with the D{null} detector. Agreement between data and standard model predictions is observed. A 95% confidence level upper exclusion limit for the {sigma}(p{bar p} {yields} ZH) x BR(H {yields} b{bar b}) channel is set between 3.2-8.2 pb for Higgs masses of 105 to 145 GeV.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Standard Theory of Particle Physics by : Luciano Maiani
Download or read book The Standard Theory of Particle Physics written by Luciano Maiani and published by World Scientific Publishing Company. This book was released on 2016-08-25 with total page 483 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives a quite complete and up-to-date picture of the Standard Theory with an historical perspective, with a collection of articles written by some of the protagonists of present particle physics. The theoretical developments are described together with the most up-to-date experimental tests, including the discovery of the Higgs Boson and the measurement of its mass as well as the most precise measurements of the top mass, giving the reader a complete description of our present understanding of particle physics.
Book Synopsis A Search for the Higgs Boson in the ZH Channel with the D-zero Detector at the Fermilab Tevatron Collider by : James Matthew Heinmiller
Download or read book A Search for the Higgs Boson in the ZH Channel with the D-zero Detector at the Fermilab Tevatron Collider written by James Matthew Heinmiller and published by . This book was released on 2006 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: This analysis describes a search for a standard model Higgs boson produced in association with a Z boson through the decay mode ZH → e+e -bb in pp collisions at s = 1.96 TeV at the Fermilab Tevatrot Collider. The data sample used in this analysis corresponds to 452 pb-1 of integrated luminosity accumulated with the DO detector. Agreement between data and standard model predictions is observed. A 95% confidence level upper exclusion limit for the sigma(pp → ZH x BR(H → bb) channel is set between 3.2--8.2 pb for Higgs masses of 105 to 145 GeV.
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