Search For The Decays Of Stopped Exotic Long Lived Particles Produced In P P Collisions At 13 Tev At Cms
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A Search For Exotic Higgs Decays
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Author : Jackson Burzynski
language : en
Publisher: Springer Nature
Release Date : 2023-05-23
A Search For Exotic Higgs Decays written by Jackson Burzynski and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-05-23 with Science categories.
The absence of new physics at the TeV scale observed thus far at the Large Hadron Collider (LHC) motivates an increasing focus on searches for weakly-coupled new particles and exotic signatures. In particular, particles with macroscopic mean proper lifetimes, known as long-lived particles (LLPs), are of significant interest due to their ability to elude the majority of searches which rely on the assumption that Beyond Standard Model particles decay close to the primary interaction point. Many models which aim to solve various issues with the Standard Model (SM) introduce new particles with lifetimes that are either unconstrained, or even shown to prefer the macroscopic regime. These theories often point to the Higgs boson as a possible portal to new physics, with exotic Higgs decays being the primary phenomenological consequence and means of discovery. It is well motivated both from theory and experimental constraints to consider the scenario in which the particles produced in these exotic decays have macroscopic proper lifetimes and give rise to unique detector signatures. This work describes a search for exotic decays of the Higgs boson to two long-lived, neutral, spin-0 particles which subsequently decay to pairs of b quarks, giving the striking signature of displaced hadronic jets in the ATLAS inner detector. Several other ATLAS searches have probed this decay topology previously, excluding branching ratios of the Higgs boson to LLPs of more than 10% for proper lifetimes greater than 100mm. These searches relied on dedicated triggers designed to select events with LLPs decaying in the ATLAS calorimeter or muon spectrometer. The lack of an equivalent trigger for LLP decays in the ATLAS inner detector has been a limiting factor in probing LLP lifetimes less than 100mm. To circumvent the difficulty of triggering on LLP decays, the search presented in this thesis exploits the ZH associated production mode, relying on leptonic trigger signatures to select interesting events. This is the first search for Higgs boson decays into LLPs to exploit this analysis methodology and additionally makes use of several novel methods for both background rejection and background estimation. No excess over Standard Model predictions is observed, and upper limits are set on the branching ratio of the Higgs boson to LLPs . Depending on the mass of the LLP, branching ratios greater than 10% are excluded for lifetimes as small as 4mm and as large as 100mm, probing an important gap in the ATLAS exotic Higgs decay programme. In comparison to the previous searches for Higgs decays to LLPs, these are among the most stringent limits placed on this scenario, and for LLPs with masses below 40 GeV these results represent the strongest existing constraints on the branching ratio of the Higgs boson to LLPs in this lifetime regime.
Search For The Decays Of Stopped Exotic Long Lived Particles Produced In P P Collisions At 13 Tev At Cms
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Author : Weifeng Ji
language : en
Publisher:
Release Date : 2018
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 has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Large Hadron Collider (France and Switzerland) categories.
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.
The Physics Associated With Neutrino Masses
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Author : Diego Aristizabal Sierra
language : en
Publisher: Frontiers Media SA
Release Date : 2020-01-13
The Physics Associated With Neutrino Masses written by Diego Aristizabal Sierra and has been published by Frontiers Media SA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-01-13 with categories.
This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.
High Energy Physics Index
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Author :
language : en
Publisher:
Release Date : 1986
High Energy Physics Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with Nuclear physics categories.
Search For Decays Of Stopped Long Lived Particles Produced In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2015
Search For Decays Of Stopped Long Lived Particles Produced In Proton Proton Collisions At Sqrt S 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.
A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6 fb-1 of 8 TeV proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of 13.2+3.6 -2.5 events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass ≤1000 GeV and a top squark with mass ≤525 GeV are excluded, for lifetimes between 1 μs and 1000 s. Finally, these results are the most stringent constraints on stopped particles to date.
Search For Decays Of Stopped Long Lived Particles Produced In Proton Proton Collisions At Arrow
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Author :
language : en
Publisher:
Release Date : 2015
Search For Decays Of Stopped Long Lived Particles Produced In Proton Proton Collisions At Arrow 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.
Search For Stopped Long Lived Particles Produced In Pp Collisions At 8 Tev At Cms
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Author : Marissa L. Rodenburg
language : en
Publisher:
Release Date : 2014
Search For Stopped Long Lived Particles Produced In Pp Collisions At 8 Tev At Cms written by Marissa L. Rodenburg and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
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.
Science Citation Index
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Author :
language : en
Publisher:
Release Date : 1993
Science Citation Index written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Science categories.
Vols. for 1964- have guides and journal lists.
Search For Long Lived Particles Using Delayed Photons In Proton Proton Collisions At 13 Tev With The Cms Detector
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Author : Kevin Patrick McDermott
language : en
Publisher:
Release Date : 2019
Search For Long Lived Particles Using Delayed Photons In Proton Proton Collisions At 13 Tev With The Cms Detector written by Kevin Patrick McDermott and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
This dissertation presents a search for long-lived particles using delayed photons in proton-proton collisions at sqrt(s) = 13 TeV recorded by the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider in 2017, corresponding to an integrated luminosity of 41.5 fb^-1. This analysis includes a number of unique components that will be discussed: a dedicated signal trigger, out-of-time photon reconstruction and identification, and a detector time resolution measurement. The results of this search include the combination of a related analysis using data collected in 2016 also at sqrt(s) = 13 TeV, corresponding to a combined integrated luminosity of 77.4 fb^-1. The combined results are interpreted in the context of supersymmetry with gauge-mediated supersymmetry breaking, where the neutralino is long-lived and decays to a photon and a gravitino. Limits are presented as a function of the neutralino proper decay length and mass. For neutralino proper decay lengths of 10^1, 10^2, 10^3, and 10^4 cm, masses up to 320, 525, 360, and 215 GeV are excluded at 95% confidence level, respectively. Additionally, a discussion on a high-performance computing upgrade to CMS, known as mkFit, will be presented. mkFit is an on-going effort to exploit highly parallel computer architectures in vectorizing and parallelizing combinatorial Kalman filter charged particle track reconstruction algorithms. The current physics and computational performance of this project will be discussed.
A Search For Exotic Particles Decaying To Wz Pairs In Pp Collisions At S
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Author :
language : en
Publisher:
Release Date : 2012
A Search For Exotic Particles Decaying To Wz Pairs In Pp Collisions At S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
A search for exotic particles decaying via WZ to final states with electrons and muons is performed using a data sample of pp collisions collected at 7 TeV center-of-mass energy by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.98 fb-1. A cross section measurement for the production of WZ is also performed on a subset of the collision data. No significant excess is observed over the Standard Model background, so lower bounds at the 95% confidence level are set on the production cross sections of hypothetical particles decaying to WZ in several theoretical scenarios. Assuming the Sequential Standard Model, W' bosons with masses below 1143 GeV/c2 are excluded. New limits are also set for several configurations of Low-Scale Technicolor.