Search For Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At 2
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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 Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At 2
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Author :
language : en
Publisher:
Release Date : 2016
Search For Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At 2 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.
Search For Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At 2
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Author :
language : en
Publisher:
Release Date : 2015
Search For Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At 2 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.
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.
Search For Pair Produced Long Lived Neutral Particles Decaying To Jets In The Atlas Hadronic Calorimeter In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2015
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 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 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.
Search For Neutral Long Lived Particles In Pp Collisions At Square Root S
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Author : [Study Group] ATLAS Collaboration CERN
language : en
Publisher:
Release Date : 2022
Search For Neutral Long Lived Particles In Pp Collisions At Square Root S written by [Study Group] ATLAS Collaboration CERN 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: 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
Chemical Abstracts
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Author :
language : en
Publisher:
Release Date : 2002
Chemical Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Chemistry categories.
Search For Long Lived Neutral Particles Decaying To Quark Antiquark Pairs In Proton Proton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2015
Search For Long Lived Neutral Particles Decaying To Quark Antiquark Pairs In Proton Proton Collisions At U221a 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 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.
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp Collisions At Arrow
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Author :
language : en
Publisher:
Release Date : 2015
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp 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.
Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb-1 of data collected by the ATLAS detector in [arrow]" = 8 TeV proton-proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for R-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. The analysis is performed using a requirement on the number of jets, in combination with separate requirements on the number of b-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results are interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass m-g
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp Collisions At Root S
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Author :
language : en
Publisher:
Release Date : 2015
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp Collisions At Root 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.
Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb-1 of data collected by the ATLAS detector in [arrow]" TeV proton-proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for R-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. Our analysis was performed using a requirement on the number of jets, in combination with separate requirements on the number of b-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results were interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass mg~
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2015
Search For Massive Supersymmetric Particles Decaying To Many Jets Using The Atlas Detector In Pp Collisions At U221a 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.
Results of a search for decays of massive particles to fully hadronic final states are presented. This search uses 20.3 fb-1 of data collected by the ATLAS detector in √8 TeV proton-proton collisions at the LHC. Signatures based on high jet multiplicities without requirements on the missing transverse momentum are used to search for R-parity-violating supersymmetric gluino pair production with subsequent decays to quarks. Our analysis was performed using a requirement on the number of jets, in combination with separate requirements on the number of b-tagged jets, as well as a topological observable formed from the scalar sum of the mass values of large-radius jets in the event. Results were interpreted in the context of all possible branching ratios of direct gluino decays to various quark flavors. No significant deviation is observed from the expected Standard Model backgrounds estimated using jet counting as well as data-driven templates of the total-jet-mass spectra. Gluino pair decays to ten or more quarks via intermediate neutralinos are excluded for a gluino with mass mg ̃ 1 TeV for a neutralino mass msub?0̃ 1/sub = 500 GeV. Direct gluino decays to six quarks are excluded for msubg