Estimation Of The Invisible Z Background To Hadronic Supersymmetry Searches Performed With Proton Proton Collision Data At 7 And 8 Tev Observed With The Cms Detector During The First Run Of The Cern Large Hadron Collider
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Estimation Of The Invisible Z Background To Hadronic Supersymmetry Searches Performed With Proton Proton Collision Data At 7 And 8 Tev Observed With The Cms Detector During The First Run Of The Cern Large Hadron Collider
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Author : Jared Todd Sturdy
language : en
Publisher:
Release Date : 2013
Estimation Of The Invisible Z Background To Hadronic Supersymmetry Searches Performed With Proton Proton Collision Data At 7 And 8 Tev Observed With The Cms Detector During The First Run Of The Cern Large Hadron Collider written by Jared Todd Sturdy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Large Hadron Collider (France and Switzerland) categories.
In searches for SUSY in all-hadronic channels, events with jets and a Z boson form an irreducible background when the Z boson decays to a pair of neutrinos. For R-parity conserving Susy models, every decay chain involving a superparticle must result in at least one lightest supersymmetric particle (LSP), which can be neutral and noninteracting. The detector signature for the LSP is identical to that of the two neutrinos from the Z, which appear as an imbalance in the transverse momentum of the event. The characterization of these types of events is crucially important in any search for new physics performed in a multi-jets+missing transverse momentum channel. A method for estimating this irreducible background using events with a measured photon is presented, and the results for a search performed in the all-hadronic multi-jet channel are shown to be consistent with standard model expectations. Limits are set on the mass of expected new particles in various models.
Search For Supersymmetry In 8 Tev Proton Proton Collision Events With Bottom Quark Jets And Missing Transverse Energy
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Author : Benjamin Kreis
language : en
Publisher:
Release Date : 2014
Search For Supersymmetry In 8 Tev Proton Proton Collision Events With Bottom Quark Jets And Missing Transverse Energy written by Benjamin Kreis 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.
A search for supersymmetry in a sample of proton-proton collision events with a center-of-mass energy of 8 TeV is presented. The sample, collected with the Compact Muon Solenoid detector at the Large Hadron Collider, corresponds to an integrated luminosity of 19.4 fb[-]1 . Events are required to have large missing transverse energy, at least three jets, and at least one identified bottom-quark jet. Numbers of events in exclusive bins of the scalar sum of jet transverse momentum values, missing transverse energy, and bottom-quark jet multiplicity are found to be consistent with the standard model expectations. The results are interpreted as 95% confidence level upper limits on simplified supersymmetric models approximating gluino mediated bottom- and top-squark production.
Heavy Neutral Particle Decays To Tau Pairs In Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2012
Heavy Neutral Particle Decays To Tau Pairs In 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 2012 with categories.
This thesis describes a study of the tau-pair final state in proton collisions at a center of mass energy of 7 TeV using the CMS Experiment at the CERN Large Hadron Collider. Tau leptons usually decay to hadrons and their efficient detection is very challenging in a hadronic environment. A novel tau reconstruction algorithm that maintains tau detection efficiency for low background rates was developed. Events were then selected from the CMS 2011 data sample in three T T final states depending on the tau decays: mu + T (h), e+ T (h), e+mu where T (h) denotes a hadronic tau decay. Those events were used to measure the Z-boson production cross section where Z yields T T . A search for the Standard Model and Minimal Supersymmetric Standard Model (MSSM) Higgs bosons was also performed. No signal was observed in the Higgs search and stringent new bounds were set for the SM Higgs production and in the MSSM parameter space.
Estimation Of The Z Vv Background To New Physics Searches In Atlas
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Author : Tanya Sandoval
language : en
Publisher:
Release Date : 2013
Estimation Of The Z Vv Background To New Physics Searches In Atlas written by Tanya Sandoval and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
This thesis describes a series of studies related to searches for new phenomena, beyond the Standard Model of particle physics, in high energy hadron collisions. In such searches, it becomes crucial to identify the Standard Model backgrounds in order to resolve a potential new signal. The thesis presents a method that uses photon events to determine one of such backgrounds, caused by the production of Z boson events. The studies performed to validate the method, both theoretically and experimentally, are presented and the method was shown to be successful as well as to provide reliable results. Theoretically, the method is found to be robust up to a ~10% uncertainty. Experimentally, the method is implemented to estimate the Z(vv) + jets background for the SUSY 0l + E_T miss + jets search in the ATLAS experiment at the Large Hadron Collider, where this background is one of the most important components for the final sensitivity and is impossible to measure directly. The main experimental results presented are the latest from ATLAS at the time of writing, corresponding to the full dataset of proton-proton collisions delivered by the LHC in 2011 (4.7 fb -1) at a centre of mass energy of 7 TeV. Given that this method has been mainstream since 2010, brief comparisons to the results from previous analyses that used smaller datasets with the same centre of mass energy are also given, as well as additional cross-checks that support the robustness and validity of the method. The results presented here have contributed to the determination of the world's best limits with respect to SUSY models, which currently exclude equal mass squarks and gluinos below 1.4 TeV.
A Search For Supersymmetry In Events With A Z Boson Jets And Missing Transverse Energy In Pp Collisions With Sqrt S
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Author : Tova Ray Holmes
language : en
Publisher:
Release Date : 2016
A Search For Supersymmetry In Events With A Z Boson Jets And Missing Transverse Energy In Pp Collisions With Sqrt S written by Tova Ray Holmes 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 new phenomena in final states containing a Z boson decaying to electrons or muons, jets, and large missing transverse momentum is presented. This search uses proton--proton collision data collected during 2015 and 2016 at a center of mass energy sqrt(s)=13 TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb-1. The search targets the pair production of supersymmetric particles, squarks or gluinos, which decay via jets and a Z boson to the lightest Supersymmetric particle, which does not interact with the ATLAS detector. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.3 (1.0) TeV.
Z Boson Cross Section Measurements And Neutral Higgs Boson Search In The Di Muon Channel With The Cms Detector
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Author : Xinmei Niu (Ph. D.)
language : en
Publisher:
Release Date : 2019
Z Boson Cross Section Measurements And Neutral Higgs Boson Search In The Di Muon Channel With The Cms Detector written by Xinmei Niu (Ph. D.) 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.
In this thesis, measurements of inclusive and differential Z boson production cross sections in proton-proton collisions at [square root of] s =13 TeV with the CMS detector at Large Hadron Collider are performed with the di-muon channel. The measured total inclusive cross section times branching ratio is or(pp - ZX) x [beta](Z --> [mu][mu]) = 1870 ± 2(stat) ± 35(syst) ± 51(lumi) pb for the di-muon invariant mass in the range of 60 to 120 GeV, which is in good agreement with the next-to-next-to leading order QCD predictions. The spectra of Z boson transverse momentum, ... variable, rapidity, and the muon transverse momentum are also measured and compared with theoretical predictions. The large production cross section of Z boson and good experimental accessibility of final-state muons permit a real-time monitoring of luminosities using the counts of reconstructed Z --> [mu][mu] events. Preliminary results of counting of Z bosons as a luminometer are shown using the entire 2018 data-taking period. A search for beyond Standard Model neutral Higgs bosons decaying to two muons is also presented. No significant excess is observed. A 95% confidence level upper limit is set on ... The exclusion contour is also determined on the parameter phase space in the context of Minimal Supersymmetric Standard Mode representative benchmark scenarios.
Search For Top Squark Pairs Decaying Into Higgs Or Z Bosons In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2014
Search For Top Squark Pairs Decaying Into Higgs Or Z Bosons 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 2014 with categories.
Our search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton–proton collisions at √s= 8TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5 fb-1. The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark mass eigenstate t̃/sup2 source decaying to a lighter top-squark mass eigenstate t̃/sup2 via either t̃/sup2 → Ht̃/sup1 or tsup̃/sup2 →Ztsup̃/sup1, followed in both cases by tsup̃/sup1→ t?sup0̃1, where ?sup0̃1 source is an undetected, stable, lightest supersymmetric particle. The interpretation is performed in the region where the mass difference between the tsup̃/sup1 and ?sup0̃1 states is approximately equal to the top-quark mass (mt1-msup?01≃mt), which is not probed by searches for direct tsup̃/sup1 squark pair production. This analysis excludes top squarks with mass mt1 575 GeVand msubt2
Summary Of The Atlas Experiment S Sensitivity To Supersymmetry After Lhc Run 1 Interpreted In The Phenomenological Mssm
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Author : Simone Amoroso
language : en
Publisher:
Release Date : 2015
Summary Of The Atlas Experiment S Sensitivity To Supersymmetry After Lhc Run 1 Interpreted In The Phenomenological Mssm written by Simone Amoroso 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.
Abstract: A summary of the constraints from the ATLAS experiment on R-parity-conserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb−1 of proton-proton collision data at centre-of-mass energies of s√=7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented
Measurements Of Zh And Wh Production In The H Bb Decay Channel In Pp Collisions At 13 Tev With The Atlas Detector
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Author : ATLAS Collaboration CERN
language : en
Publisher:
Release Date : 2020
Measurements Of Zh And Wh Production In The H Bb Decay Channel In Pp Collisions At 13 Tev With The Atlas Detector written by 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 2020 with categories.
Abstract: Measurements are presented of the Standard Model Higgs boson decaying into a bb ̄ pair and produced in association with a W or Z boson decaying into leptons, using proton-proton collision data collected between 2015 and 2018 by the ATLAS detector. The measurements use data delivered by the Large Hadron Collider at a centre-of-mass energy of s√=13 TeV, corresponding to an integrated luminosity of 139 fb−1. The production of a Higgs boson in association with a W or Z boson is established, with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions
Measurement Of The Z Tau Tau Production Cross Section In Proton Proton Collisions At Square Root Of S
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Author : Justin Griffiths
language : en
Publisher:
Release Date : 2012
Measurement Of The Z Tau Tau Production Cross Section In Proton Proton Collisions At Square Root Of S written by Justin Griffiths and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Large Hadron Collider (France and Switzerland) categories.
The first measurement of the inclusive cross-section of the Z boson decaying to two tau leptons was measured with the ATLAS detector at the LHC. The data sample in this analysis represents an integrated luminosity of 35 pb ̄1 of proton-proton collisions at a center of mass energy of sqrt(s)=7 TeV. Separate measurements were performed in four decay modes based on how the two tau leptons decay: to hadrons and an electron, to hadrons and a muon, to an electron and a muon, and to two muons. In all four final states, inclusive cross-section measurements were made both in the fiducial region of the ATLAS detector where acceptance is high and in the full phase space, restricted to the mass range of [66, 116] GeV. The measurements from the four individual channels were then combined to yield the combined Z --> [tau] [tau] cross-section of 970 ± 70 (stat.) ± 60 (sys.) ± 30 (lumi.) pb.