Download or read book Heavy Neutral Particle Decays to Tau Pairs in Proton Collisions at Sqrt s written by and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Heavy Neutral Particle Decays to Tau Pairs written by Michail Bachtis and published by Springer. This book was released on 2013-12-30 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Search for Heavy Resonances Decaying to Tau Lepton Pairs in Proton proton Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Heavy Neutral Particle Decays to Tau Pairs written by Michail Bachtis and published by Springer Science & Business Media. This book was released on 2013-12-13 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Search for Long lived Neutral Particles Decaying to Quark antiquark Pairs in Proton proton Collisions at u221A s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Search for Heavy Resonances Decaying to Taus in 7 TeV Proton proton Collisions at the Large Hadron Collider written by Alfredo Gurrola and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book A Search for Long Lived Neutral Particles Decaying to Hadronic States in Proton proton Collisions in the ATLAS Detector at Sqrt s written by Rachel Rosten and published by . This book was released on 2017 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Chaptong sani written by and published by . This book was released on 1920 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Pair produced Resonances Decaying to Jet Pairs in Proton u2013 proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4 fb–1 of integrated luminosity from proton–proton collisions at a center-of-mass energy of 8 TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385 GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350 GeV at 95% confidence level. Furthermore, previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835 GeV.
Download or read book Search for Narrow High mass Resonances in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Search for Neutral Color Octet Weak Triplet Scalar Particles in Proton Proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for pair production of neutral color-octet weak-triplet scalar particles ([Theta]0) is performed in processes where one [Theta]0 decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons. The search is performed with data collected by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 19.7 fb-1 of proton-proton collisions at √s = 8 TeV. The number of observed events is found to be in agreement with the standard model predictions. The 95% confidence level upper limit on the product of the cross section and branching fraction is obtained as a function of the [Theta]0 mass. The 95% confidence level lower bounds on the [Theta]0 mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model.
Download or read book Search for W Decaying to Tau Lepton and Neutrino in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: We found that the first search for a heavy charged vector boson in the final state with a tau lepton and a neutrino is reported, using 19.7 fb-1 of LHC data at √s = 8 TeV. A signal would appear as an excess of events in kinematic regions where the standard model background is low. No excess is observed. Limits are set on a model in which the W' decays preferentially to fermions of the third generation. Our results substantially extend previous constraints on this model. Masses below 2.0 to 2.7 TeV are excluded, depending on the model parameters. In addition, the existence of a W' boson with universal fermion couplings is excluded at 95% confidence level, for W' masses below 2.7 TeV.
Download or read book A Search for New Physics with High Mass Tau Pairs in Proton antiproton Collisions at square Root S written by Zongru Wan and published by . This book was released on 2005 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Search for t overline t Resonances Using Lepton plus jets Events in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb-1 of proton-proton collision data collected at a centre-of-mass energy of \(\sqrt{s}=8 \) TeV. The lepton-plus-jets final state is used, where the top pair decays to \({W}^{+}b{W}^{-}\overline{b} \), with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with [Gamma]/m = 15% decaying to \(t\overline{t} \). These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.
Download or read book Search for a Heavy Neutral Particle Decaying to E Mu E Tau Or Mu Tau in Pp Collisions at u221A s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e±?∓, e±?∓, or ?±?∓ using 20.3 fb-1 of pp collision data at √s=8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ????????? in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z' vector boson.
Download or read book Searches for Dijet Resonances written by Lydia Audrey Beresford and published by Springer. This book was released on 2018-09-04 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses one of the most intriguing mysteries of our universe: the nature of dark matter. The results presented here mark a significant and substantial contribution to the search for new physics, in particular for new particles that couple to dark matter. The first analysis presented is a search for heavy new particles that decay into pairs of hadronic jets (dijets). This pioneering analysis explores unprecedented dijet invariant masses, reaching nearly 7 TeV, and sets constraints on several important new physics models. The two subsequent analyses focus on the difficult low dijet mass region, down to 200 GeV, and employ a novel technique to efficiently gather low-mass dijet events. The results of these analyses transcend the long-standing constraints on dark matter mediator particles set by several existing experiments.
Download or read book Particle Physics at the Tercentenary of Mikhail Lomonosov written by Moskovskiĭ gosudarstvennyĭ universitet im. M.V. Lomonosova and published by World Scientific. This book was released on 2013 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
