A Search for New Physics with High Mass Tau Pairs in Proton-antiproton Collisions at [square Root] S PDF Download
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![A Search for New Physics with High Mass Tau Pairs in Proton-antiproton Collisions at [square Root] S PDF](https://books.google.com/books/content/images/frontcover/c2WkYgEACAAJ?fife=w150-h200)
Author: Zongru Wan
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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![A Search for New Physics with High Mass Tau Pairs in Proton-antiproton Collisions at [square Root] S PDF](https://books.google.com/books/content/images/frontcover/c2WkYgEACAAJ?fife=w80-h100)
Author: Zongru Wan
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Author:
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Category :
Languages : en
Pages :
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Author:
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Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 173
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We present the results of a search for new particles decaying to tau pairs using the data corresponding to an integrated luminosity of 195 pb-1 collected from March 2002 to September 2003 with the CDF detector at the Tevatron. Hypothetical particles, such as Z' and MSSM Higgs bosons can potentially produce the tau pair final state. We discuss the method of tau identification, and show the signal acceptance versus new particle mass. The low-mass region, dominated by Z → ??, is used as a control region. In the high-mass region, we expect 2.8 ± 0.5 events from known background sources, and observe 4 events in the data sample. Thus no significant excess is observed, and we set upper limits on the cross section times branching ratio as a function of the masses of heavy scalar and vector particles.
Author: Michail Bachtis
Publisher: Springer Science & Business Media
ISBN: 3319032577
Category : Science
Languages : en
Pages : 161
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The work presented in this thesis spans a wide range of experimental particle physics subjects, starting from level-1 trigger electronics to the final results of the search for Higgs boson decay and to tau lepton pairs. The thesis describes an innovative reconstruction algorithm for tau decays and details how it was instrumental in providing a measurement of Z decay to tau lepton pairs. The reliability of the analysis is fully established by this measurement before the Higgs boson decay to tau lepton pairs is considered. The work described here continues to serve as a model for analysing CMS Higgs to tau leptons measurements.
Author: Carsten Noeding
Publisher:
ISBN:
Category :
Languages : en
Pages : 190
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During the last decades, particle physicists have studied the tiniest building blocks of matter--the quarks and the leptons--and the forces between them in great detail. From these experiments, a theoretical framework has been built that describes the observed results with high precision. The achievement of this theory, which is referred to as the Standard Model of elementary particle physics, was the elaboration of a unified description of the strong, weak and electromagnetic forces in the framework of quantum gauge-field theories. Moreover, the Standard Model combines the weak and electromagnetic forces in a single electroweak gauge theory. The fourth force which is realized in nature, gravity, is too weak to be observable in laboratory experiments carried out in high-energy particle physics and is not part of the Standard Model. Although the Standard Model has proven highly successful in correlating a huge amount of experimental results, a key ingredient is as yet untested: the origin of electroweak symmetry breaking. Currently, the only viable ansatz that is compatible with observation is the Higgs mechanism. It predicts the existence of a scalar particle, called the Higgs boson, and the couplings to the fundamental Standard Model particles, however not its mass. An upper limit on the mass of the Higgs boson of {approx} 1 TeV can be inferred from unitarity arguments. One of the key tasks of particle physics in the next years will be to verify the existence of this particle. The introduction of an elementary scalar particle in a quantum field theory is highly problematic. The Higgs boson mass is subject to large quantum corrections, which makes it difficult to understand how its mass can be less than a TeV as required by theory. In addition, the Standard Model does not provide an answer to fundamental questions like the values of free parameters of the model, the pending integration of gravity or the evolution of the coupling constants of the fundamental forces at large energy regimes. Hence there are strong reasons to believe that the Standard Model is only a low-energy approximation to a more fundamental theory. One of the best studied candidates for an extension of the Standard Model is supersymmetry, which predicts the existence of a supersymmetric partner for each fundamental particle that differs only in spin. To allow different masses for Standard Model particles and their corresponding supersymmetric partners, supersymmetry must be broken. The mechanism behind supersymmetry breaking is currently unknown, however, various hypotheses exist. Supersymmetric models do not only solve the problem of the large quantum corrections to the Higgs boson mass, but they also allow the unification of the coupling constants at a common scale. In addition, certain supersymmetric models provide a suitable candidate for cold dark matter, which represents a large fraction of mass in our universe. Searches for supersymmetric particles have been performed by the four LEP experiments (ALEPH, DELPHI, L3, OPAL) up to the kinematic limit. Since no evidence for supersymmetric particles has been found, lower limits on their masses have been derived. The search for supersymmetry is now continuing at the Tevatron collider, located at the Fermi National Accelerator Laboratory in Batavia, Illinois. Two dedicated detector systems, CDF and D0, are installed at the Tevatron to analyze proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. A particular promising discovery channel for supersymmetry within the Tevatron energy range is the trilepton channel. In this channel, the lighter supersymmetric partners of the Higgs and gauge bosons, the charginos and neutralinos, decay into final states with leptons or hadrons and missing energy. Using the leptonic final states, the signal can be separated from the large Standard Model background. Supersymmetry requires an extension of the Standard Model Higgs sector, leading to more than one neutral Higgs boson. Enhanced couplings result in sizable cross sections for Higgs boson production, and the decay into a tau pair becomes an important Higgs boson discovery channel. Within the present thesis, a search for new physics predicted by constrained supersymmetric models is performed in final states consisting of an electron and a tau using data collected with the D0 detector from April 2002 to July 2004. The first analysis searches for the associated production of the lightest chargino and the second lightest neutralino in final states with an electron, a hadronically decaying tau, an additional lepton and missing transverse energy: e + {tau}{sub h} + {ell} + E{sub T}. The second analysis searches for neutral supersymmetric Higgs bosons in the decay mode {phi} {yields} {tau}{tau} {yields} e + {tau}{sub h} + E{sub T}. To improve the sensitivity, the results are interpreted in combination with other channels.
![A Search for New Physics in Photon-lepton Events in Proton-antiproton Collisions at [square Root] S PDF](https://books.google.com/books/content/images/frontcover/5hd4NwAACAAJ?fife=w80-h100)
Author: Jeffrey W. Berryhill
Publisher:
ISBN:
Category : Collisions (Nuclear physics)
Languages : en
Pages : 198
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 23
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A search for a narrow, high-mass resonance decaying into Z and Higgs (H) bosons is presented. The final state studied consists of a merged jet pair and a [tau] pair resulting from the decays of Z and H bosons, respectively. This analysis is based on a data sample of proton-proton collisions at a center-ofmass energy of 8 TeV, collected with the CMS experiment in 2012, and corresponding to an integrated luminosity of 19.7 fb-1. In the resonance mass range of interest, which extends from 0.8 to 2.5 TeV, the Z and H bosons are produced with large momenta, which implies that the final products of the two quarks or the two [tau] leptons must be detected within a small angular interval. A combination of all possible decay modes of the [tau] leptons, production cross sections in a range between 0.9 and 27.8 fb are excluded at 95% confidence level, depending on the resonance mass.
Author:
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Category :
Languages : en
Pages :
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A search for heavy resonances that decay to tau lepton pairs is performed using proton-proton collisions at \sqrt{s}$ = 13 TeV. The data were collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 2.2 inverse femtobarns. The observations are in agreement with standard model predictions. An upper limit at 95% confidence level on the product of the production cross section and branching fraction into tau lepton pairs is calculated as a function of the resonance mass. For the sequential standard model, the presence of Z' bosons decaying into tau lepton pairs is excluded for Z' masses below 2.1 TeV, extending previous limits for this final state. For the topcolor-assisted technicolor model, which predicts Z' bosons that preferentially couple to third-generation fermions, Z' masses below 1.7 TeV are excluded, representing the most stringent limit to date.
Author:
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ISBN:
Category :
Languages : en
Pages :
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A search for the resonant production of high-mass photon pairs is presented. The analysis is based on samples of proton-proton collision data collected by the CMS experiment at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 3.3 inverse femtobarns, respectively. The search focuses on spin-0 and spin-2 resonances with masses between 0.5 and 4 TeV and with widths, relative to the mass, between 1.4E-4 and 5.6E-2. Limits are set on scalar resonances produced through gluon-gluon fusion, and on Randall--Sundrum gravitons. A modest excess of events compatible with a narrow resonance with a mass of about 750 GeV is observed. The local significance of the excess is approximately 3.4 standard deviations. The significance is reduced to 1.6 standard deviations once the effect of searching under multiple signal hypotheses is considered. More data are required to determine the origin of this excess.
