Search for Massive, Long-lived Particles in Final States with a Multi-track Displaced Vertex and an Electron in Pp Collisions at √s PDF Download
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Author: Nimrod Taiblum
Publisher:
ISBN:
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Languages : en
Pages : 114
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Author: Nimrod Taiblum
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Book Description
Author:
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Languages : en
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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.
Author: Lesya Horyn
Publisher: Springer Nature
ISBN: 3030916723
Category : Science
Languages : en
Pages : 146
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This thesis presents a search for long-lived particles decaying into displaced electrons and/or muons with large impact parameters. This signature provides unique sensitivity to the production of theoretical lepton-partners, sleptons. These particles are a feature of supersymmetric theories, which seek to address unanswered questions in nature. The signature searched for in this thesis is difficult to identify, and in fact, this is the first time it has been probed at the Large Hadron Collider (LHC). It covers a long-standing gap in coverage of possible new physics signatures. This thesis describes the special reconstruction and identification algorithms used to select leptons with large impact parameters and the details of the background estimation. The results are consistent with background, so limits on slepton masses and lifetimes in this model are calculated at 95% CL, drastically improving on the previous best limits from the Large Electron Positron Collider (LEP).
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Languages : en
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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.
Author: Dan Quach
Publisher:
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Category :
Languages : en
Pages : 0
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We report the results of a search for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of √s = 13 TeV. The data were collected by the CMS detector during the full Run 2 data taking period from 2015 through 2018, corresponding to a total integrated luminosity of 140/fb. This search targets pair-produced long-lived particles with a mean proper decay length between 0.1 and 100 mm that each decay into at least two quarks. The signature is a pair of displaced vertices each formed from many tracks. This search extends a previous CMS search using the 2015 and 2016 dataset, with improvements in background rejection, background estimation techniques, as well as uncertainty estimation. Results are compared with R-parity violating supersymmetry models that predict pair-produced long-lived particles, each decaying into multijet or dijet final states. No events are observed with two reconstructed high-track-multiplicity vertices. For models of long-lived pair-produced neutralinos, gluinos, and top squarks, pair-production cross sections larger than 0.08 fb at 95% confidence level are excluded for masses between 800 and 3000 GeV and mean proper decay lengths between 1 and 25 mm. In the gluino model, masses up to 2500 GeV are excluded for mean proper decay lengths between 0.6 and 90 mm. In the neutralino model, masses up to 1100 GeV are excluded for mean proper decay lengths between 0.6 and 70 mm. For the top squark model, masses up to 1600 GeV are excluded for mean proper decay lengths between 0.4 and 80 mm.
Author: Chang Wei Loh
Publisher:
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Category :
Languages : en
Pages :
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Author: Rudolf Frühwirth
Publisher: Springer Nature
ISBN: 303065771X
Category : Electronic books
Languages : en
Pages : 208
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This open access book is a comprehensive review of the methods and algorithms that are used in the reconstruction of events recorded by past, running and planned experiments at particle accelerators such as the LHC, SuperKEKB and FAIR. The main topics are pattern recognition for track and vertex finding, solving the equations of motion by analytical or numerical methods, treatment of material effects such as multiple Coulomb scattering and energy loss, and the estimation of track and vertex parameters by statistical algorithms. The material covers both established methods and recent developments in these fields and illustrates them by outlining exemplary solutions developed by selected experiments. The clear presentation enables readers to easily implement the material in a high-level programming language. It also highlights software solutions that are in the public domain whenever possible. It is a valuable resource for PhD students and researchers working on online or offline reconstruction for their experiments.
![Search for Heavy Long-lived Multi-charged Particles in Pp Collisions at [arrow]](https://books.google.com/books/content/images/frontcover/ThKZAQAACAAJ?fife=w80-h100)
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Languages : en
Pages :
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A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at [arrow]" = 8 TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb-1 are examined. Particles producing anomalously high ionisation, consistent with long-lived massive particles with electric charges from.
Author: Marissa L. Rodenburg
Publisher:
ISBN:
Category :
Languages : en
Pages :
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At the Large Hadron Collider counter-rotating proton beams are collided at sqrt(s) = 8 TeV. The Compact Muon Solenoid (CMS) is used to measure the energies and charges of the resulting cascade of particles produced in these collisions. This search focuses on the observation of massive, long-lived particles, such as the gluino, that would suggest new physics beyond the Standard Model. A custom trigger is used to probe time periods during which no proton collisions occur, thereby eliminating most backgrounds to the signal. The remaining backgrounds resulting from cosmic rays, beam-related effects, and instrumental noise, are further reduced using a series of sophisticated selection cuts. Candidate events passing all selection cuts are analyzed using a counting experiment and limits are placed on the cross sections and masses of the gluino and the supersymmetric top quark.
![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 PDF](https://books.google.com/books/content/images/frontcover/r-bazwEACAAJ?fife=w80-h100)
Author: [Study Group] ATLAS Collaboration CERN
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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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
