Heavy Neutral Particle Decays to Tau Pairs in Proton Collisions at Sqrt(s) PDF Download
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Languages : en
Pages : 0
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This thesis describes a study of the tau-pair final state in proton collisions at a center of mass energy of 7 TeV using the CMS Experiment at the CERN Large Hadron Collider. Tau leptons usually decay to hadrons and their efficient detection is very challenging in a hadronic environment. A novel tau reconstruction algorithm that maintains tau detection efficiency for low background rates was developed. Events were then selected from the CMS 2011 data sample in three T T final states depending on the tau decays: mu + T (h), e+ T (h), e+mu where T (h) denotes a hadronic tau decay. Those events were used to measure the Z-boson production cross section where Z yields T T . A search for the Standard Model and Minimal Supersymmetric Standard Model (MSSM) Higgs bosons was also performed. No signal was observed in the Higgs search and stringent new bounds were set for the SM Higgs production and in the MSSM parameter space.
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Languages : en
Pages : 0
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Book Description
This thesis describes a study of the tau-pair final state in proton collisions at a center of mass energy of 7 TeV using the CMS Experiment at the CERN Large Hadron Collider. Tau leptons usually decay to hadrons and their efficient detection is very challenging in a hadronic environment. A novel tau reconstruction algorithm that maintains tau detection efficiency for low background rates was developed. Events were then selected from the CMS 2011 data sample in three T T final states depending on the tau decays: mu + T (h), e+ T (h), e+mu where T (h) denotes a hadronic tau decay. Those events were used to measure the Z-boson production cross section where Z yields T T . A search for the Standard Model and Minimal Supersymmetric Standard Model (MSSM) Higgs bosons was also performed. No signal was observed in the Higgs search and stringent new bounds were set for the SM Higgs production and in the MSSM parameter space.
Author: Michail Bachtis
Publisher: Springer
ISBN: 9783319032566
Category : Science
Languages : en
Pages : 152
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Book Description
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: Michail Bachtis
Publisher: Springer Science & Business Media
ISBN: 3319032577
Category : Science
Languages : en
Pages : 161
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Book Description
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.
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Languages : en
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A search is performed for long-lived massive neutral particles decaying to quark-antiquark pairs. The experimental signature is a distinctive topology of a pair of jets, originating at a secondary vertex. Events were collected with the CMS detector at the CERN LHC in proton-proton collisions at a center-of-mass energy of 8 TeV. The data analyzed correspond to an integrated luminosity of 18.5 fb–1. No significant excess is observed above standard model expectations. Upper limits at 95% confidence level are set on the production cross section of a heavy neutral scalar particle, H, in the mass range of 200 to 1000 GeV, decaying promptly into a pair of long-lived neutral X particles in the mass range of 50 to 350 GeV, each in turn decaying into a quark-antiquark pair. For X with mean proper decay lengths of 0.4 to 200 cm, the upper limits are typically 0.5–200 fb. The results are also interpreted in the context of an R-parity-violating supersymmetric model with long-lived neutralinos decaying into a quark-antiquark pair and a muon. For pair production of squarks that promptly decay to neutralinos with mean proper decay lengths of 2–40 cm, the upper limits on the cross section are typically 0.5–3 fb. As a result, the above limits are the most stringent on these channels to date.
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Languages : en
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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.
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Languages : en
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Author: Alfredo Gurrola
Publisher:
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Category :
Languages : en
Pages :
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Book Description
Over the last few decades, the Standard Model (SM) of particle physics has been used as a means of understanding the world around us. However, there is an increasing amount of data that suggests the SM of particle physics only describes nature up to energies of the electroweak scale. Extensions to the SM have been developed as a means of explaining experimental observation. If these extensions are indeed the correct mathematical descriptions of nature, the Large Hadron Collider (LHC), located at the European Center for Nuclear Research (CERN) near Geneva, Switzerland, is expected to produce new and exciting physics signatures that can shed light on the evolution of our universe since the early hypothesized Big Bang. Of particular interest are models that may lead to events with highly energetic tau lepton pairs. In this dissertation, focus is placed on a possible search for new heavy gauge bosons decaying to highly energetic tau pairs using a data sample corresponding to an integrated luminosity of 36 pb−1 of proton-proton collisions at [square root of] s = 7 TeV collected with the CMS detector at the CERN LHC. The number of observed events in the data is in good agreement with the predictions for SM background processes. In the context of the Sequential SM, a Zʹ with mass less than 468 GeV/c2 is excluded at 95%credibility level, exceeding the sensitivity by the Tevatron experiments at the Fermi National Accelerator Laboratory.
Author: Rachel Rosten
Publisher:
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Category :
Languages : en
Pages : 180
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A search for the decay of a heavy scalar boson into pairs of long-lived neutral particles in \intlumi of proton proton collisions at $\sqrt{s}=8$~TeV and $3.2~\rm{fb}^{-1}$ at $\sqrt{s}=13$~TeV in the ATLAS detector is presented. The search focuses on final states where both long lived particles decay within the hadronic calorimeter of the detector, resulting in jets with unusual properties. No excess was observed and limits were set on the lifetime of the long lived particles for various combinations of scalar boson and long lived particle masses.
Author: Moskovskiĭ gosudarstvennyĭ universitet im. M.V. Lomonosova
Publisher: World Scientific
ISBN: 9814436828
Category : Science
Languages : en
Pages : 481
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Book Description
This volume is devoted to a wide variety of investigations, both in theory and experiment, of particle physics such as electroweak theory, fundamental symmetries, tests of the Standard Model and beyond, neutrino and astroparticle physics, heavy quark physics, non-perturbative QCD, quantum gravity effects, and present and future accelerator physics.
Author: Alexander I Studenikin
Publisher: World Scientific
ISBN: 9814436844
Category : Science
Languages : en
Pages : 481
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Book Description
This volume is devoted to a wide variety of investigations, both in theory and experiment, of particle physics such as electroweak theory, fundamental symmetries, tests of the Standard Model and beyond, neutrino and astroparticle physics, heavy quark physics, non-perturbative QCD, quantum gravity effects, and present and future accelerator physics.
