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Search For Particles Decaying To Tt Pairs Through The Di Lepton Decay Mode Using The Atlas Detector At Cern
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Book Synopsis Search for Particles Decaying to Tt Pairs Through the Di-lepton Decay Mode Using the ATLAS Detector at CERN. by : Robin Eamonn Long
Download or read book Search for Particles Decaying to Tt Pairs Through the Di-lepton Decay Mode Using the ATLAS Detector at CERN. written by Robin Eamonn Long and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Heavy Neutral Particle Decays to Tau Pairs by : Michail Bachtis
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.
Book Synopsis A Search for Tt Resonances in the Single Lepton Final State with the ATLAS Experiment by : Andrew David Altheimer
Download or read book A Search for Tt Resonances in the Single Lepton Final State with the ATLAS Experiment written by Andrew David Altheimer and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for undiscovered particles decaying into top-antitop quark pairs produced in proton-proton collisions with the ATLAS experiment at the Large Hadron Collider utilizing 20.3 fb$^-1$ of data collected at $\sqrt{s}=8$ \tev\ center-of-mass energy during the 2012 data taking period is presented. The invariant mass spectrum of events containing multiple jets, exactly one lepton, and missing transverse energy and which are consistent with the decay of a top-antitop quark pair is studied and found to be consistent with that predicted by the Standard Model. Upper limits on the production cross section times branching ratio of several benchmark signal models are set at a 95\% confidence level.
Book Synopsis Search for Long-lived Particles Decaying to Oppositely Charged Lepton Pairs with the ATLAS Experiment at √s by : Dominik Krauss
Download or read book Search for Long-lived Particles Decaying to Oppositely Charged Lepton Pairs with the ATLAS Experiment at √s written by Dominik Krauss and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for Pair-produced Long-lived Neutral Particles Decaying to Jets in the ATLAS Hadronic Calorimeter in Pp Collisions at √2 by :
Download or read book Search for Pair-produced Long-lived Neutral Particles Decaying to Jets in the ATLAS Hadronic Calorimeter in Pp Collisions at √2 written by and published by . This book was released on 2015 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb-1 of data collected in proton-proton collisions at [arrow]"=8 TeV. This research is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.
Book Synopsis Search for Events with Two Displaced Vertices from Pair-produced Neutral Long-lived Particles Decaying to Hadronic Jets in the Muon Spectrometer of the ATLAS Detector with Full Run 2 Data by : Audrey Kvam
Download or read book Search for Events with Two Displaced Vertices from Pair-produced Neutral Long-lived Particles Decaying to Hadronic Jets in the Muon Spectrometer of the ATLAS Detector with Full Run 2 Data written by Audrey Kvam and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This analysis is a search for events with two displaced vertices reconstructed from the decay of pair-produced neutral, weakly-interacting, long-lived particles using the muon spectrometer of the ATLAS detector. The search uses a model-independent strategy, and employs a custom trigger for reconstructing displaced hadronic jets in the muon spectrometer with 139 fb-1 of pp collision data at [square root of]s=13 TeV collected in Run 2 at the LHC. The results are interpreted in terms of a Higgs scalar portal model, which probes the existence of a hidden sector that weakly couples to the Standard Model. The search observed 0 events in the signal region, which is compatible with the expected background of 0.32 ± 0.05 events. Limits were set on long-lived particle lifetime for all simulated signal mass points. For the Higgs boson with a mass of 125 GeV, the analysis reports the first exclusion limits for branching fractions into neutral long-lived particles below 0.1%, while branching fractions above 10% are excluded at 95% confidence level for long-lived particle proper lifetimes ranging from 4 cm to 72.4 m. In addition, the analysis presents the first results for the decay of long-lived particles into tt ̅ in the ATLAS muon spectrometer.
Book Synopsis Search for the Decays of Stopped Exotic Long-lived Particles Produced in P-P Collisions at 13 TeV at CMS by : Weifeng Ji
Download or read book Search for the Decays of Stopped Exotic Long-lived Particles Produced in P-P Collisions at 13 TeV at CMS written by Weifeng Ji and published by . This book was released on 2018 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I present the searches looking for decays of stopped massive long-lived exotic particles, which are pair produced in the proton-proton collisions at 13 TeV and come to rest afterwards in the CMS detector at the CERN LHC. The decays are most likely to be observed when there are no collisions. Two specific decay scenarios are studied: a long-lived particle (LLP) decaying hadronically or semi- leptonically in the calorimeter, and a LLP decaying semi-leptonically or leptonically to a pair of muons in the muon detector. The calorimeter-based search is performed using 2.7 fb-1 of 13 TeV collision run data collected in 2015 and 35.9 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 721 hours. The muon search is performed using 2.8 fb-1 of 13 TeV collision run data collected in 2015 and 36.2 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 744 hours. Search results are interpreted in a couple of simplified models. The limits on the production cross sections and masses of LLPs are calculated as a function of particle lifetimes, which vary from 100 ns to 10 days, assuming the corresponding decaying branching fractions to be 100%. The results are the most stringent ones on the stopped LLPs so far.
Book Synopsis Search for Events with a Pair of Displaced Vertices from Long-lived Neutral Particles Decaying Into Hadronic Jets in the ATLAS Muon Spectrometer in Pp Collisions at [square Root] S by : [Study Group] ATLAS Collaboration CERN
Download or read book Search for Events with a Pair of Displaced Vertices from Long-lived Neutral Particles Decaying Into Hadronic Jets in the ATLAS Muon Spectrometer in Pp Collisions at [square Root] S written by [Study Group] ATLAS Collaboration CERN and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A search for events with two displaced vertices from long-lived particle (LLP) pairs using data collected by the ATLAS detector at the LHC is presented. This analysis uses 139 fb−1 of proton-proton collision data at √s=13 TeV recorded in 2015-2018. The search employs techniques for reconstructing vertices of LLPs decaying to jets in the muon spectrometer displaced between 3 and 14 m with respect to the primary interaction vertex. The observed numbers of events are consistent with the expected background and limits for several benchmark signals are determined. For the Higgs boson with a mass of 125 GeV, the paper reports the first exclusion limits for branching fractions into neutral long-lived particles below 0.1%, while branching fractions above 10% are excluded at 95% confidence level for LLP proper lifetimes ranging from 4 cm to 72.4 m. In addition, the paper present the first results for the decay of LLPs into t ̄t in the ATLAS muon spectrometer
Book Synopsis Search for Pair-produced Long-lived Neutral Particles Decaying to Jets in the ATLAS Hadronic Calorimeter in Pp Collisions at {u221A} S by :
Download or read book Search for Pair-produced Long-lived Neutral Particles Decaying to Jets in the ATLAS Hadronic Calorimeter in Pp Collisions at {u221A} S written by and published by . This book was released on 2015 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3 fb-1 of data collected in proton–proton collisions at √s=8 TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle mass from 10 GeV to 150 GeV.
Book Synopsis The Standard Model Higgs Boson by : Martin B. Einhorn
Download or read book The Standard Model Higgs Boson written by Martin B. Einhorn and published by North Holland. This book was released on 1991 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 8.
Book Synopsis Search for Neutral Long-lived Particles in Pp Collisions at [square Root]s by : [Study Group] ATLAS Collaboration CERN
Download or read book Search for Neutral Long-lived Particles in Pp Collisions at [square Root]s written by [Study Group] ATLAS Collaboration CERN and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A search for decays of pair-produced neutral long-lived particles (LLPs) is presented using 139 fb−1 of proton-proton collision data collected by the ATLAS detector at the LHC in 2015-2018 at a centre-of-mass energy of 13 TeV. Dedicated techniques were developed for the reconstruction of displaced jets produced by LLPs decaying hadronically in the ATLAS hadronic calorimeter. Two search regions are defined for different LLP kinematic regimes. The observed numbers of events are consistent with the expected background, and limits for several benchmark signals are determined. For a SM Higgs boson with a mass of 125 GeV, branching ratios above 10% are excluded at 95% confidence level for values of c times LLP mean proper lifetime in the range between 20 mm and 10 m depending on the model. Upper limits are also set on the cross-section times branching ratio for scalars with a mass of 60 GeV and for masses between 200 GeV and 1 TeV
Book Synopsis Search for Long-lived Neutral Particles Decaying to Quark-antiquark Pairs in Proton-proton Collisions at {u221A}s by :
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 CERN Courier written by and published by . This book was released on 2016 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for Lepton-flavor VViolation in Z-boson Decays with [tau] Leptons with the ATLAS Detector by : ATLAS Collaboration CERN
Download or read book Search for Lepton-flavor VViolation in Z-boson Decays with [tau] Leptons with the ATLAS Detector written by ATLAS Collaboration CERN and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for Long-lived Particles that Decay Into Final States Containing Two Electrons Or Two Muons in Proton-proton Collisions at $\sqrt{s} by :
Download or read book Search for Long-lived Particles that Decay Into Final States Containing Two Electrons Or Two Muons 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 is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) fb-1 in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at √s=8 TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle's mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV/c2 decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV/c2, each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV/c2), the limits are in the range 2-50 fb. As a result, these limits are sensitive to Higgs boson branching fractions as low as 10-4.
Book Synopsis Search for Massive, Long-lived Particles Using Multitrack Displaced Vertices Or Displaced Lepton Pairs in [math Display by :
Download or read book Search for Massive, Long-lived Particles Using Multitrack Displaced Vertices Or Displaced Lepton Pairs in [math Display written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. In this study, this analysis uses a data sample of proton-proton collisions at \(\sqrt{s} = 8\) TeV corresponding to an integrated luminosity of 20.3 fb−1 collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios.
Book Synopsis Higgs Boson Decays into a Pair of Bottom Quarks by : Cecilia Tosciri
Download or read book Higgs Boson Decays into a Pair of Bottom Quarks written by Cecilia Tosciri and published by Springer Nature. This book was released on 2021-10-22 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.
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