A Search For Quasi Long Lived Supersymmetric Particles Within The Cms Detector At The Lhc
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A Search For Quasi Long Lived Supersymmetric Particles Within The Cms Detector At The Lhc
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Author : Michael Kenneth Squires
language : en
Publisher:
Release Date : 2015
A Search For Quasi Long Lived Supersymmetric Particles Within The Cms Detector At The Lhc written by Michael Kenneth Squires and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
This dissertation presents a search for supersymmetry (SUSY), an extension to the stan- dard model (SM) of particle physics, with mass-degenerate co-next-to-lightest-stable parti- cles (co-NLSP). These co-NLSP particles are sleptons: either a selectron or smuon. Both of these co-NLSP sleptons undergo decay to their standard model counterparts and a nearly massless gravitino. We analyze a dataset of 19.4 fb−1 collected during run one operations at the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider which ran at an 8 TeV center-of-mass collision energy. The co-NLSP sleptons in this model are quasistable, producing decays within the detector volume. We construct a custom analysis object com- posed of pairs of tracks that form a vertex at high precision. Tracks in events that pass trigger cuts which use initial and final state radiation from the hard co-NLSP pair production process, as well as the missing transverse energy from the gravitino are candidates for inclusion in this custom analysis object. We impose a series of offline selection cuts designed to separate possible beyond SM decay signatures from mundane backgrounds such as quasielastic scattering or select standard model decays like charged kaon or sigma decay. We take tuples that pass these selection criterion and boost the putative daughter particle into the putative mother particle's reference frame to form a spectrum in p* which, under the assumption of a decay at a specified mass configuration, produces a delta distribution that is smeared via resolution effects into a signal shape originating from decay. We observe at most three events in the data at the low end of our search region (100 GeV mother mass), which falls to zero events at a slepton mother mass of 260 GeV. These spectra are fit using a likelihood model with the signal probability density function being derived from simulation and the background selected as an exponential. Using Bayesian statistics and the profile likelihood technique we set limits on the co-NLSP slepton production cross section for masses between 100-210 GeV with proper lifetimes up to c[tau] = 93 cm.
The 10th International Conference On Supersymmetry And Unification Of Fundamental Interactions
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Author : Pran Nath
language : en
Publisher:
Release Date : 2002
The 10th International Conference On Supersymmetry And Unification Of Fundamental Interactions written by Pran Nath and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Grand unified theories (Nuclear physics) categories.
Search For New Physics With Long Lived Particles Decaying To Photons And Missing Energy In Pp Collisions At A Center Of Mass Energy Of 7 Tev With The Cms Experiment At The Lhc
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Author : Hongliang Liu
language : en
Publisher:
Release Date : 2011
Search For New Physics With Long Lived Particles Decaying To Photons And Missing Energy In Pp Collisions At A Center Of Mass Energy Of 7 Tev With The Cms Experiment At The Lhc written by Hongliang Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Gauge invariance categories.
We perform a search for long-lived neutral particles decaying into a photon and invisible particles in pp collisions at a center-of-mass energy of 7 TeV at the Large Hadron Collider. In the context of gauge mediated supersymmetry with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest supersymmetric particle, the neutralino can decay into a gravitino and a photon with a non-zero lifetime. The impact parameter of the photon relative to the beam-beam collision point can be reconstructed using converted photons. The method is sensitive to lifetimes of the order of [Special characters omitted.] (0.1 ns). The data sample corresponds to an integrated luminosity of 2.1 ± 0.1 fb -1 recorded in the first part of 2011 by the CMS experiment at the LHC at [Special characters omitted.] = 7 TeV. The search is performed using events containing photons, missing transverse energy and jets. Upper limits at the 95% confidence level are presented on the cross section for such particles from pair-production, each of which decays into a photon and invisible particles.
Search For Long Lived Supersymmetric Particles Using Displaced Vertices With The Atlas Detector At The Lhc
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Author : Emily Anne Thompson
language : en
Publisher:
Release Date : 2022
Search For Long Lived Supersymmetric Particles Using Displaced Vertices With The Atlas Detector At The Lhc written by Emily Anne Thompson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Abstract: The existence of long-lived particles (LLPs) is a common feature in many theories beyond the Standard Model. For example, models with small couplings (i.e. R-parity-violating supersymmetry) and models allowing for decays via highly virtual intermediate states (i.e. Split supersymmetry) predict the presence of LLPs. With lifetimes ranging from picoseconds to nanoseconds, massive LLPs could decay to several electrically charged particles in the inner tracking volume of the ATLAS detector at the Large Hadron Collider, resulting in the reconstruction of a displaced secondary vertex. This thesis presents the first search for high mass, multi-track displaced vertices and multiple energetic jets using the full Run-2 dataset collected by the ATLAS detector, corresponding to an integrated luminosity of 139 fb−1 at s√=13 TeV. The observed event yields are compatible with those expected from background processes. The results are presented as exclusion limits at 95 % confidence level on supersymmetric scenarios with non-zero R-parity violating couplings. This thesis also presents the ATLAS FastTracKer (FTK), which is a hardware-based track finder envisioned to be integrated into the ATLAS trigger system. The trigger system is responsible for selecting interesting events with a high purity at a rate of only 1 kHz. The FTK was designed to provide tracking information of all charged particles with pT>1 GeV in the ATLAS inner detector, which is a powerful discriminant for selecting interesting events. The training of the FTK system to achieve a high track-finding efficiency and the adaptability of the system to new detector conditions is presented. Furthermore, the applicability of the system to select candidate events containing long-lived particles is described
A Search For Long Lived Particles That Stop In The Cms Detector And Decay To Muons
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Author :
language : en
Publisher:
Release Date : 2016
A Search For Long Lived Particles That Stop In The Cms Detector And Decay To Muons written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A search for long-lived particles that are produced in proton-proton collisions at the CERN LHC, come to rest in the CMS detector, and decay to muons is presented. The decays of the stopped particles could be observed during the intervals between LHC beam crossings, at times that are well separated from any proton-proton collisions. The analysis uses 19.7 1/fb of 8 TeV data collected by CMS in 2012, during a search interval of 293 hours of trigger livetime. Massive, long-lived particles do not exist in the Standard Model, and so any sign of them would be an indication of new physics. The results are interpreted with a model that predicts a long-lived particle that has a charge of twice the electron charge and that behaves like a lepton. Cross section limits are set for each long-lived particle mass as a function of lifetime, for lifetimes between 100 ns and 10 days. These are the first limits for long-lived stopped particles that decay to muons.
Search For Supersymmetry In Hadronic Final States
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Author : Hannsjörg Artur Weber
language : en
Publisher: Springer
Release Date : 2015-06-11
Search For Supersymmetry In Hadronic Final States written by Hannsjörg Artur Weber and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-06-11 with Science categories.
The project reported here was a search for new super symmetric particles in proton-proton collisions at the LHC. It has produced some of the world’s best exclusion limits on such new particles. Furthermore, dedicated simulation studies and data analyses have also yielded essential input to the upgrade activities of the CMS collaboration, both for the Phase-1 pixel detector upgrade and for the R&D studies in pursuit of a Phase-2 end cap calorimeter upgrade.
The Fate Of Long Lived Superparticles With Hadronic Decays After Lhc Run 1
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Author :
language : en
Publisher:
Release Date : 2015
The Fate Of Long Lived Superparticles With Hadronic Decays After Lhc Run 1 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Supersymmetry searches at the LHC are both highly varied and highly constraining, but the vast majority are focused on cases where the final-stage visible decays are prompt. Scenarios featuring superparticles with detector-scale lifetimes have therefore remained a tantalizing possibility for sub-TeV SUSY, since explicit limits are relatively sparse. Nonetheless, the extremely low backgrounds of the few existing searches for collider-stable and displaced new particles facilitates recastings into powerful long-lived superparticle searches, even for models for which those searches are highly non-optimized. In this paper, we assess the status of such models in the context of baryonic R-parity violation, gauge mediation, and mini-split SUSY. We explore a number of common simplified spectra where hadronic decays can be important, employing recasts of LHC searches that utilize different detector systems and final-state objects. The LSP/NLSP possibilities considered here include generic colored superparticles such as the gluino and light-flavor squarks, as well as the lighter stop and the quasi-degenerate Higgsino multiplet motivated by naturalness. We find that complementary coverage over large swaths of mass and lifetime is achievable by superimposing limits, particularly from CMS's tracker-based displaced dijet search and heavy stable charged particle searches. Adding in prompt searches, we find many cases where a range of sparticle masses is now excluded from zero lifetime to infinite lifetime with no gaps. In other cases, the displaced searches furnish the only extant limits at any lifetime.
Displaced Vertices
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Author : Dan Quach
language : en
Publisher:
Release Date : 2020
Displaced Vertices written by Dan Quach and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
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.
Search For Supersymmetry In Pp Collisions At S 8 Tev With A Photon Lepton And Missing Transverse Energy
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Author : Yutaro Iiyama
language : en
Publisher: Springer
Release Date : 2017-06-14
Search For Supersymmetry In Pp Collisions At S 8 Tev With A Photon Lepton And Missing Transverse Energy written by Yutaro Iiyama and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-06-14 with Science categories.
This Ph.D. thesis is a search for physics beyond the standard model (SM) of particle physics, which successfully describes the interactions and properties of all known elementary particles. However, no particle exists in the SM that can account for the dark matter, which makes up about one quarter of the energy-mass content of the universe. Understanding the nature of dark matter is one goal of the CERN Large Hadron Collider (LHC). The extension of the SM with supersymmetry (SUSY) is considered a promising possibilities to explain dark matter. The nominated thesis describes a search for SUSY using data collected by the CMS experiment at the LHC. It utilizes a final state consisting of a photon, a lepton, and a large momentum imbalance probing a class of SUSY models that has not yet been studied extensively. The thesis stands out not only due to its content that is explained with clarity but also because the author performed more or less all aspects of the thesis analysis by himself, from data skimming to limit calculations, which is extremely rare, especially nowadays in the large LHC collaborations.
Search For Supersymmetry In Hadronic Final States
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Author : Hannsjörg Artur Weber
language : en
Publisher:
Release Date : 2015
Search For Supersymmetry In Hadronic Final States written by Hannsjörg Artur Weber and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
The project reported here was a search for new supersymmetric particles in proton-proton collisions at the LHC. It has produced some of the world's best exclusion limits on such new particles. Furthermore, dedicated simulation studies and data analyses have also yielded essential input to the upgrade activities of the CMS collaboration, both for the Phase-1 pixel detector upgrade and for the R&D studies in pursuit of a Phase-2 endcap calorimeter upgrade.