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A Search For The Neutral Higgs Bosons Of The Minimal Supersymmetric Standard Model With The Atlas Detector At The Large Hadron Collider
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Book Synopsis A Search for the Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model with the ATLAS Detector at the Large Hadron Collider by : John Stakely Keller
Download or read book A Search for the Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model with the ATLAS Detector at the Large Hadron Collider written by John Stakely Keller and published by . This book was released on 2013 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM), produced in proton-proton collisions recorded by the ATLAS detector, is presented. The data correspond to an integrated luminosity of 20.3 fb−1, with a center of mass energy of 8 TeV. The search focuses on final states where the Higgs bosons decay into a [tau]+[tau]− pair, with one [tau] lepton decaying leptonically and the other hadronically. Two analyses are performed which separately target low-mass and high-mass Higgs bosons, with the former divided into two sub-channels based on the presence or absence of a b-jet in final state. No evidence of new Higgs bosons is found, and upper limits are set on the cross-section times branching ratio of such Higgs bosons, and on the MSSM parameters m [Alpha] and tan [Beta].
Book Synopsis Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in the Tau_e Tau_mu Decay Mode at Sqrt(s) by : Holger von Radziewski
Download or read book Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in the Tau_e Tau_mu Decay Mode at Sqrt(s) written by Holger von Radziewski and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for Supersymmetry Using a Higgs Boson in the Decay Cascade with the ATLAS Detector at the Large Hadron Collider by : Claire David
Download or read book Search for Supersymmetry Using a Higgs Boson in the Decay Cascade with the ATLAS Detector at the Large Hadron Collider written by Claire David and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Standard Model of particle physics is a successful theory, yet it is incomplete. Supersymmetry is one of the favoured extensions of the Standard Model, elegantly addressing several unresolved issues. This thesis presents a search for the pair production of supersymmetric particles chargino one and neutralino two, where the neutralino two decays to the lightest neutralino and the 125 GeV Higgs boson. The final states considered for the search have large missing transverse momentum, an isolated lepton and two jets identified as originating from bottom quarks. The analysis is based on 20.3 inverse femtobarns of 8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. No excess over Standard Model predictions is observed. The analysis has been combined with three independent searches that probe other decay modes of the Standard Model Higgs boson. Limits are set at 95% confidence level in the context of a simplified supersymmetric model. Common masses of chargino one and neutralino two are excluded up to 250 GeV for a massless neutralino one. The analysis of this dissertation has been reinterpreted in the context of a large scan of the phenomenological Minimal Supersymmetric Standard Model, along with 22 other ATLAS Run 1 searches. The resulting summary paper represents the most comprehensive assessment of the ATLAS constraints on Supersymmetry models to date.
Book Synopsis Search for the Standard Model Higgs Boson in the H to Tau+ Tau- Decay Mode in Sqrt(s) by :
Download or read book Search for the Standard Model Higgs Boson in the H to Tau+ Tau- Decay Mode in Sqrt(s) written by and published by . This book was released on 2014 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is performed on data from proton-proton collisions at a centre-of-mass energy of 8TeV collected with the ATLAS detector at the Large Hadron Collider. The samples used for this search were collected in 2012 and correspond to integrated luminosities in the range 19.5-20.3 fb-1. The MSSM Higgs bosons are searched for in the [tau] [tau] final state. No significant excess over the expected background is observed, and exclusion limits are derived for the production cross section times branching fraction of a scalar particle as a function of its mass. The results are also interpreted in the MSSM parameter space for various benchmark scenarios.
Book Synopsis Beyond Standard Model Collider Phenomenology of Higgs Physics and Supersymmetry by : Marc Christopher Thomas
Download or read book Beyond Standard Model Collider Phenomenology of Higgs Physics and Supersymmetry written by Marc Christopher Thomas and published by Springer. This book was released on 2016-08-01 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies collider phenomenology of physics beyond the Standard Model at the Large Hadron Collider (LHC). It also explores in detail advanced topics related to Higgs boson and supersymmetry – one of the most exciting and well-motivated streams in particle physics. In particular, it finds a very large enhancement of multiple Higgs boson production in vector-boson scattering when Higgs couplings to gauge bosons differ from those predicted by the Standard Model. The thesis demonstrates that due to the loss of unitarity, the very large enhancement for triple Higgs boson production takes place. This is a truly novel finding. The thesis also studies the effects of supersymmetric partners of top and bottom quarks on the Higgs production and decay at the LHC, pointing for the first time to non-universal alterations for two main production processes of the Higgs boson at the LHC–vector boson fusion and gluon–gluon fusion. Continuing the exploration of Higgs boson and supersymmetry at the LHC, the thesis extends existing experimental analysis and shows that for a single decay channel the mass of the top quark superpartner below 175 GeV can be completely excluded, which in turn excludes electroweak baryogenesis in the Minimal Supersymmetric Model. This is a major new finding for the HEP community. This thesis is very clearly written and the introduction and conclusions are accessible to a wide spectrum of readers.
Book Synopsis A Beauty-ful Boson by : Giulia Di Gregorio
Download or read book A Beauty-ful Boson written by Giulia Di Gregorio and published by Springer Nature. This book was released on 2023-01-01 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: The analysis described in this thesis is the search for the Higgs boson, decaying into bb pair, in the associated production with a vector boson, in the extreme Higgs boson transverse momentum region where the Higgs boson is reconstructed using the large-R jet technique. The use of the large-R jets allows to add a part of the phase space unexplored so far, which is particularly sensitive to possible new physics. The analysed data have been collected at LHC by the ATLAS detector between 2015 and 2018 at a centre-of-mass energy of √s = 13 TeV. The same dataset has been used to perform the differential pp → ZH and pp → WH cross-section measurements used to extract the information on the Higgs couplings and to put limits on Beyond the Standard Model effects. Furthermore the analysis has been re-used to perform a cross-section measurement of the diboson ZZ and WZ processes because the diboson and the Higgs processes have a similar topology. For the first time the ZZ(bb) and WZ(bb) cross-sections are measured at √s = 13 TeV and the observed cross-section measurements are consistent with the Standard Model predictions.
Book Synopsis Search for the Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in the Tau_lep Tau_had Decay Mode with the ATLAS Experiment by : Sascha Thoma
Download or read book Search for the Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in the Tau_lep Tau_had Decay Mode with the ATLAS Experiment written by Sascha Thoma and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zusammenfassung: This thesis describes the search for the neutral Higgs Bosons of the Minimal Supersymmetric Standard Model. The Higgs boson decay mode considered is the decay into tau leptons with one electron or muon and one hadronically decaying tau lepton in the final state. The p-p collision data analysed have been recorded in 2010 and 2011 with the ATLAS experiment at an centre-of-mass energy of 7 TeV and corresponds to an integrated luminosity of about 4.7/fb
Book Synopsis Search for Neutral Higgs Bosons Decaying Into the Leptonic-hadronic Di-tau Final State in the Minimal Supersymmetric Standard Model with the ATLAS Detector by : Felix Friedrich
Download or read book Search for Neutral Higgs Bosons Decaying Into the Leptonic-hadronic Di-tau Final State in the Minimal Supersymmetric Standard Model with the ATLAS Detector written by Felix Friedrich and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Searches for New Physics at Colliders by : My Phuong Thi Le
Download or read book Searches for New Physics at Colliders written by My Phuong Thi Le and published by Stanford University. This book was released on 2011 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: The turning-on of the Large Hadron Collider is the momentous milestone in our quest for new physics beyond the Standard Model. Soon, we will be presented with the task of detecting, identifying, and studying the possibly large parameter space of the underlying model. In this thesis, we will look at some possible extensions to the SM, their signatures at colliders, and possible search strategies to explore the new physics in a model-independent way. In chapter 2, we study the extended neutral gauge sector of the Littlest Higgs model at the 500 GeV e+e- collider using the fermion pair production and Higgs associate production channel. We find that these channels can provide an accurate determination of the fundamental parameters and thus allows the verification of the little Higgs mechanism designed to cancel the Higgs mass quadratic divergence. In chapter 3, we study the ATLAS supersymmetry searches proposed for the 14 TeV pp collider using the $\sim$ 70k models of the phenomenological Minimal Supersymmetric Model (pMSSM) moldel set, that have survived many theoretical and experimental constraints. Since pMSSM does not make any simplifying assumptions about its SUSY-breaking mechanism at high scale, this encompasses a broad class of Supersymmetric models. We find that even though these searches were optimized mostly for mSUGRA signals, they are relatively robust in observing the more general pMSSM models. For the case of models in which squarks and gluinos have mass below 1 TeV, essentially all of these models ($> 99\%$) were observable in at least one of these searches, with 1 $fb^{-1}$ of integrated luminosity allowing for an uncertainty of 50\% in the SM background. We found that 0-lepton searches are the most powerful searches, while searches with 1-2 leptons do not have coverage as good as has been shown for mSUGRA. We then study possible reasons why a model could not be observed. These difficult models mostly include those with long-lived charginos which lead to small Missing Tranverse Energy (MET) and models with squeezed spectra which lead to soft jets that fail the jet cuts. In chapter 4, we study similar searches that have been carried out by ATLAS at the 7 TeV LHC. We found that systematic uncertainty again plays an important role in determining the coverage of the searches. This is especially true for searches with a large SM background, such as $n$-jet 0 lepton searches. We study the implication of a null result from the 7 TeV LHC. We find that the degree of fine-tuning in the pMSSM depends on the prior in which we scan our 19-dimensional space, but overall it is not as large as in mSUGRA. We find that a null result at the 7 TeV with $10 fb^{-1}$ and 20\% systematic errors would imply a need for a higher energy e+e- machine than the 500 GeV ILC to study Supersymmetry. Continuing on along the line of Supersymmetry, in chapter 5 we explore the possibility of adding one more generation to the MSSM (4GMSSM). We find that the CP-odd A boson can be very light due to the contribution of the heavy 4th generation fermion loops while all other Higgs particles (including the CP-even {\it h}) are all quite heavy. The parameter $tan(\beta)$ is strongly constrained to be between 0.5 and 2 due to perturbativity requirements on Yukawa couplings. We study the electroweak constraints as well as collider signatures on the possibility of a light A of mass $\sim$115 GeV. As for an LHC discovery, we find that this light A can be seen in the standard 2-photon Higgs search channel with cross-section more than an order of magnitude greater than that of the SM Higgs. In the last two chapters, we study possible search strategies to explore the new physics in a model-independent way. In chapter 6, we attempt to show how one could be largely agnostic about the underlying model in exploring the complete kinematically-allowed parameter space of pair-produced color octet particles (with mass $m_{\tilde{g}}$) that each directly decay into two jets plus a neutral stable particle (with mass $m_{\tilde{B}}$) that would escape the detectors and appear as MET. The kinematics of this process can be completely described by two parameters $m_{\tilde {g}}$ and $m_{\tilde {B}}$ , and in particular their splitting determines the softness or hardness of jets from the decay products. In order to cover the whole parameter space, one would need separate searches for different regions. We show that optimizing the final cuts for every ($m_{\tilde {g}}$, $m_{\tilde {B}}$) point, and combining all searches, can extend the coverage significantly. Since this is just based on the kinematics of the decay, this result can be easily interpreted for any model with this decay topology. In chapter 7, we carry this model-independent approach further in jets plus missing energy searches, by proposing that one should bin the measured data (or simulated SM background) differentially in MET and $H_T$ (scalar sum of invisible energy) for each search, and use them to set limits on any model of interest. We demonstrate this technique by carrying out a search similar to that studied in chapter 6, with one added decay step for the color octet particle, mainly it decays to 2 jets and another particle (with mass $m_{\tilde {W}}$) and it in turn decays to the neutral stable particle and 2 jets. We study different kinematic regions and set bounds in this 3-dimensional parameter space ($m_{\tilde {g}}$, $m_{\tilde {W}}$, $m_{\tilde {B}}$).
Book Synopsis Search for the Higgs Boson in the Vector Boson Fusion Channel at the ATLAS Detector by : Eric Ouellette
Download or read book Search for the Higgs Boson in the Vector Boson Fusion Channel at the ATLAS Detector written by Eric Ouellette and published by Springer. This book was released on 2015-01-20 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Thesis describes the first measurement of, and constraints on, Higgs boson production in the vector boson fusion mode, where the Higgs decays to b quarks (the most common decay channel), at the LHC. The vector boson fusion mode, in which the Higgs is produced simultaneously with a pair of quark jets, provides an unparalleled opportunity to study the detailed properties of the Higgs, including the possibility of parity and CP violation, as well as its couplings and mass. It thus opens up this new field of study for precision investigation as the LHC increases in energy and intensity, leading the way to this new and exciting arena of precision Higgs research.
Book Synopsis The theory and discovery of the Higgs boson by : Siyuan Chen
Download or read book The theory and discovery of the Higgs boson written by Siyuan Chen and published by GRIN Verlag. This book was released on 2014-09-17 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bachelor Thesis from the year 2013 in the subject Physics - Theoretical Physics, grade: 71 points, King`s College London, language: English, abstract: An overview of the steps that lead to the discovery of the Higgs boson is presented. Starting with the theoretical background framework, the Standard Model of particel physics, the Higgs field will be introduced as an addition. This extra field provides the mechanism for spontaneous symmetry breaking, that is needed to explain the existence of massive particles. An overview of the steps of the experimental search to the discovery of the Higgs boson is given in the second part of this article. Its mass has been measured to be 125.4 ± 0.4(stat) ± 0.5(sys) GeV. The Standard Model is briefly summarised. The Higgs mechanism is derived from an Abelian Model, applied to the gauge bosons of the electroweak model of Weinberg and Salam. A simple estimate of the Higgs mass is given by its derivation and the estimation of its self-coupling and vacuum expectation value. Experimental results will be presented from the CMS and ATLAS detectors at the LHC, alongside with a description of the Large Hadron Collider at CERN and possible directions for future experiments beyond the Standard Model.
Book Synopsis Search for Charged Higgs Bosons in Tau-lepton Final States with 139 Inverse Femtobarns of Proton-proton Collision Data Recorded at a Centre of Mass Energy of 13 TeV with the ATLAS Detector by : Sina Bahrasemani
Download or read book Search for Charged Higgs Bosons in Tau-lepton Final States with 139 Inverse Femtobarns of Proton-proton Collision Data Recorded at a Centre of Mass Energy of 13 TeV with the ATLAS Detector written by Sina Bahrasemani and published by . This book was released on 2019 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Higgs boson, with a measured mass of approximately $125~GeV$, has been studied extensively since its discovery in 2012 at the Large Hadron Collider. This discovery opens the question of whether the Higgs boson of the Standard Model (SM) is the only scalar particle of Nature or it belongs to a larger scalar sector, as predicted in many Beyond the Standard Model (BSM) theories. Therefore, observation of charged Higgs bosons would indicate new physics. This thesis presents results of a search for a charged Higgs boson in the mass range $80~GeV$ to $3~TeV$, through tau-lepton final states. The search is performed using proton-proton collisions data at $\sqrt{s}=13~\mbox{TeV}$, collected with the ATLAS experiment, during 2015 to 2018. The final results are interpreted in the context of the Minimal SuperSymmetric Standard Model (MSSM) benchmark scenarios. In these scenarios, charged Higgs bosons coupling to tau-lepton are enhanced for some parts of the search phase space, thus increasing the chance of their discovery. No significant excess of events above the expected background from the Standard Model processes is observed. Therefore, upper limits on the charged Higgs boson production cross section times its branching ratio to tau-lepton and its associated neutrino are set at a 95\% Confidence Level. The results are also interpreted in the context of the hMSSM and $m^{mod -}_{h}$ benchmark scenarios of the MSSM. Due to the enhancement of the charged Higgs boson coupling to tau-leptons at high values of the $\tan\beta$ parameter of the MSSM, it is possible to exclude the high $\tan\beta$ region in the $M_{H^{\pm}}$--$\tan\beta$ parameter space. In this work, $\tan\beta$ values around 60 are excluded up to a charged Higgs boson mass of $1400~\GeV$. Furthermore, in the low mass region, below $170~GeV$, all values of $\tan\beta$ in range 1--60 are excluded at 95\% confidence level.
Book Synopsis Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs in Pp Collisions at Sqrt[s] by :
Download or read book Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs in Pp Collisions at Sqrt[s] written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for neutral MSSM Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 inverse picobarns recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.
Book Synopsis Searches for Higgs Boson Pair Production in the Hh{u2192}bb??, ??WW*, ??bb, Bbbb Channels with the ATLAS Detector by :
Download or read book Searches for Higgs Boson Pair Production in the Hh{u2192}bb??, ??WW*, ??bb, Bbbb Channels with the ATLAS Detector written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Searches for both resonant and nonresonant Higgs boson pair production are performed in the hh → bb??, ??WW* final states using 20.3 fb-1 of pp collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidence-level upper limits on the production cross sections are set. These results are then combined with the published results of the hh → ??bb, bbbb analyses. An upper limit of 0.69 (0.47) pb on the nonresonant hh production is observed (expected), corresponding to 70 (48) times the SM gg → hh cross section. For production via narrow resonances, cross-section limits of hh production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. In addition, these results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.
Book Synopsis The Higgs Hunter's Guide by : John F. Gunion
Download or read book The Higgs Hunter's Guide written by John F. Gunion and published by CRC Press. This book was released on 2018-03-05 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Higgs Hunter's Guide is a definitive and comprehensive guide to the physics of Higgs bosons. In particular, it discusses the extended Higgs sectors required by those recent theoretical approaches that go beyond the Standard Model, including supersymmetry and superstring-inspired models.
Book Synopsis Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS by : Francesco Pandolfi
Download or read book Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS written by Francesco Pandolfi and published by Springer Science & Business Media. This book was released on 2013-08-15 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The theoretical foundations of the Standard Model of elementary particles relies on the existence of the Higgs boson, a particle which has been revealed for the first time by the experiments run at the Large Hadron Collider (LHC) in 2012. As the Higgs boson is an unstable particle, its search strategies were based on its decay products. In this thesis, Francesco Pandolfi conducted a search for the Higgs boson in the H → ZZ → l + l - qq Decay Channel with 4.6 fb -1 of 7 TeV proton-proton collision data collected by the Compact Muon Solenoid (CMS) experiment. The presence of jets in the final state poses a series of challenges to the experimenter: both from a technical point of view, as jets are complex objects and necessitate of ad-hoc reconstruction techniques, and from an analytical one, as backgrounds with jets are copious at hadron colliders, therefore analyses must obtain high degrees of background rejection in order to achieve competitive sensitivity. This is accomplished by following two directives: the use of an angular likelihood discriminant, capable of discriminating events likely to originate from the decay of a scalar boson from non-resonant backgrounds, and by using jet parton flavor tagging, selecting jets compatible with quark hadronization and discarding jets more likely to be initiated by gluons. The events passing the selection requirements in 4.6 fb -1 of data collected by the CMS detector are examined, in the search of a possible signal compatible with the decay of a heavy Higgs boson. The thesis describes the statistical tools and the results of this analysis. This work is a paradigm for studies of the Higgs boson with final states with jets. The non-expert physicists will enjoy a complete and eminently readable description of a proton-proton collider analysis. At the same time, the expert reader will learn the details of the searches done with jets at CMS.
Book Synopsis Discovery and Measurement of the Higgs Boson in the WW Decay Channel by : David Hall
Download or read book Discovery and Measurement of the Higgs Boson in the WW Decay Channel written by David Hall and published by Springer. This book was released on 2015-06-15 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the stand-alone discovery and measurement of the Higgs boson in its decays to two W bosons using the Run-I ATLAS dataset. This is the most precise measurement of gluon-fusion Higgs boson production and is among the most significant results attained at the LHC. The thesis provides an exceptionally clear exposition on a complicated analysis performed by a large team of researchers. Aspects of the analysis performed by the author are explained in detail; these include new methods for evaluating uncertainties on the jet binning used in the analysis and for estimating the background due to associated production of a W boson and an off-shell photon. The thesis also describes a measurement of the WW cross section, an essential background to Higgs boson production. The primary motivation of the LHC was to prove or disprove the existence of the Higgs boson. In 2012, CERN announced this discovery and the resultant ATLAS publication contained three decay channels: gg, ZZ, and WW.
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