Search For Dark Matter In Final States Containing Semi Visible Jets From Proton Proton Collisions At Square Root S
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Search For Dark Matter In Final States Containing Semi Visible Jets From Proton Proton Collisions At Square Root S
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Author : Colin Terrence Fallon
language : en
Publisher:
Release Date : 2022
Search For Dark Matter In Final States Containing Semi Visible Jets From Proton Proton Collisions At Square Root S written by Colin Terrence Fallon 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.
"This dissertation presents a novel search for new physics using the full Run 2 dataset of 137.6 fb-1 collected by the Compact Muon Solenoid during proton-proton runs of the Large Hadron Collider. The new physics in question is dark matter production in a unique signature called semi-visible jets. Semi-visible jets are produced when a new massive mediator particle emerges from the proton-proton interaction. This mediator then decays to unstable dark matter particles which hadronize and produce a mixture of standard model particles and stable dark matter particles. The stable dark particles are only detectable as missing transverse momentum, and the standard particles are detectable as jets. This produces a signature where two jets are produced, one of which is aligned with the total missing transverse momentum. The search is presented in two phases: a classical cut-based search which uses a series of cuts based on event kinematics to select events which look like the signal signature, and a machine learning based search which uses a technique called boosted decision trees to identify semi-visible jets in a more powerful but model-dependent way. No evidence for Physics Beyond the Standard Model is observed in either search. The classical search excludes the possibility that the mediator could have a mass between 1.5 TeV and 3.98 TeV, while the model-dependent search excludes mediators with masses between 1.5 TeV and 5.08 TeV. Additionally, ranges of other signal parameters are excluded"--Page viii.
Bulletin Of The Atomic Scientists
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Author :
language : en
Publisher:
Release Date : 1970-06
Bulletin Of The Atomic Scientists written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1970-06 with categories.
The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Search For The Production Of Dark Matter In Association With Top Quark Pairs In The Single Lepton Final State In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2015
Search For The Production Of Dark Matter In Association With Top Quark Pairs In The Single Lepton Final State 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 is presented for particle dark matter produced in association with a pair of top quarks in pp collisions at a centre-of-mass energy of s√=8 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 19.7 fb-1. This search requires the presence of one lepton, multiple jets, and large missing transverse energy. No excess of events is found above the SM expectation, and upper limits are derived on the production cross section. Interpreting the findings in the context of a scalar contact interaction between fermionic dark matter particles and top quarks, lower limits on the interaction scale are set. These limits are also interpreted in terms of the dark matter-nucleon scattering cross sections for the spin-independent scalar operator and they complement direct searches for dark matter particles in the low mass region.
Searching For Dark Matter With The Cms Detector In Proton Proton Collisions Containing A Single High Pt Photon And Large E Miss T
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Author : Brandon Leigh Allen
language : en
Publisher:
Release Date : 2019
Searching For Dark Matter With The Cms Detector In Proton Proton Collisions Containing A Single High Pt Photon And Large E Miss T written by Brandon Leigh Allen 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, we present a search for dark matter in final states containing a high- PT photon and large missing transverse momentum in proton-proton collisions at [square root of s] = 13 TeV using data collected by the Compact Muon Solenoid.(CMS) experiment at the CERN Large Hadron Collider (LHC) corresponding to an integrated luminosity of 35.9 inverse femtobarns. The main advances in experimental technique compared to previous searches in this final state are the use of data-driven control regions to constrain the main irreducible backgrounds from Z( --> vv̄ + [gamma] and W( --> [iota]v)+ [gamma] production and an in-depth study of the unique anomolous detector signatures that result in backgrounds due to non-collision processes. With these improvements, we have the most robust analysis of this kind presented to date. No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and limits on new physics parameters are calculated at 95% confidence level. We focus on two simplified dark matter production models where new vector and axial mediators couple a new dark dirac fermion to the Standard Model quarks. These models are chosen as they cover a large class of WIMP-like dark matter particles that show up in many types of more complete new physics models. For the two models considered, the observed (expected) lower limits on the masses of the new mediators are 950 (1150) GeV for a dark matter particle of a mass of 1 GeV.
Searching For Dark Matter With Boosted Higgs Decays In Proton Proton Collisions At Sqrt S
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Author : Nikola Lazar Whallon
language : en
Publisher:
Release Date : 2018
Searching For Dark Matter With Boosted Higgs Decays In Proton Proton Collisions At Sqrt S written by Nikola Lazar Whallon and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
If Dark Matter particles interact with Standard Model particles, it could be possible to pair produce Dark Matter particles in association with a detectable Standard Model particle at a collider such as the LHC. If this associated particle is a Higgs boson, the process is called ``mono-Higgs,'' since the resulting signature is a single Higgs boson balanced by missing energy from the undetected Dark Matter particles. Various Dark Matter models predict that this process could result in very boosted Higgs bosons that, if they decay to a pair of b-quarks, are reconstructed as jets using boosted Higgs tagging techniques. This thesis presents the results of a mono-Higgs search using 79.8 fb−1 of proton-proton collision data collected at a center-of-mass energy of 13 TeV by the ATLAS detector. The observed data are found to be consistent with the expected Standard Model backgrounds. The results are interpreted and exclusion limits are set using a Z' two-Higgs-doublet model where the pseudo-scalar Higgs particle, A, couples to Dark Matter. In order to increase the sensitivity reach of the search, new boosted Higgs tagging techniques are explored and a variable radius track jet Higgs tagging technique is employed.
The Search For The Dark Matter Signature In The Lepton Jet Final State At Sqrt S
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Author : Sergei V. Gleyzer
language : en
Publisher:
Release Date : 2011
The Search For The Dark Matter Signature In The Lepton Jet Final State At Sqrt S written by Sergei V. Gleyzer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
ABSTRACT: The Large Hadron Collider is pushing high energy physics in to a brand new territory. This extraordinary era may bring discoveries of unprecedented magnitude, delivering validation or extreme dissappointment to the physics theories of the previous decades. By colliding particles at more than 3.5 times the center of mass energy of the Tevatron accelerator at the Fermilab National Accelerator Laboratory, the CERN Large Hadron Collider aims to produce particles in the mass range above those that are already known. At the same time, there are exciting possibilities for new physics in the low-mass range that may have gone unnoticed until now. An example of this is a GeV-scale dark sector with a colorful spectrum of new particles. This physics model produces unique signatures of collimated leptons at the Large Hadron Collider energies. In the first part of this work, we describe the interesting astrophysical evidence that motivates a search for lepton jets and focus our attention on a minimal supersymmetric standard model with a GeV-scale dark sector that produces this exciting signature. In the next part of the thesis, we describe a search using the Compact Muon Solenoid (CMS) detector for evidence of dark matter in events containing muonic lepton-jets produced in 7 TeV proton-proton collisions at the Large Hadron Collider. We employ a novel lepton jet algorithm and find no evidence of an excess of such events with respect to the rate predicted by the Standard Model and interpret the null result in terms of a recently developed supersymmetric theory of dark matter. In doing so, we severely constrain the theoretical model and its parameters with the actual data from the Large Hadron Collider. In addition, we report the first observation of double J/Psi production, a new physical process discovery at the next energy frontier.
Search For Dark Matter Particles In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Dark Matter Particles 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 2016 with categories.
A search for dark matter particles directly produced in proton-proton collisions recorded by the CMS experiment at the LHC is presented. The data correspond to an integrated luminosity of 18.8 inverse femtobarns, at a center-of-mass energy of 8 TeV. The event selection requires at least two jets and no isolated leptons. The razor variables are used to quantify the transverse momentum balance in the jet momenta. The study is performed separately for events with and without jets originating from b quarks. The observed yields are consistent with the expected backgrounds and, depending on the nature of the production mechanism, dark matter production at the LHC is excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV. The use of razor variables yields results that complement those previously published.
Search For Dark Matter With Atlas
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Author : Ruth Pöttgen
language : en
Publisher: Springer
Release Date : 2018-05-31
Search For Dark Matter With Atlas written by Ruth Pöttgen and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-05-31 with Science categories.
This thesis describes in detail a search for weakly interacting massive particles as possible dark matter candidates, making use of so-called mono-jet events. It includes a detailed description of the run-1 system, important operational challenges, and the upgrade for run-2. The nature of dark matter, which accounts for roughly 25% of the energy-matter content of the universe, is one of the biggest open questions in fundamental science. The analysis is based on the full set of proton-proton collisions collected by the ATLAS experiment at the Large Hadron Collider at √s = 8 TeV. Special attention is given to the experimental challenges and analysis techniques, as well as the overall scientific context beyond particle physics. The results complement those of non-collider experiments and yield some of the strongest exclusion bounds on parameters of dark matter models by the end of the Large Hadron Collider run-1. Details of the upgrade of the ATLAS Central Trigger for run-2 are also included.
Search For Dark Matter In Events With A Highly Energetic Jet And Missing Transverse Momentum In Proton Proton Collisions At Root Out S
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Author : Ruth Pöttgen
language : en
Publisher:
Release Date : 2014
Search For Dark Matter In Events With A Highly Energetic Jet And Missing Transverse Momentum In Proton Proton Collisions At Root Out S written by Ruth Pöttgen 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.
Search For Dark Matter Extra Dimensions And Unparticles In Monojet Events In Proton Proton Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2015
Search For Dark Matter Extra Dimensions And Unparticles In Monojet Events 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.
Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing a jet and an imbalance in transverse momentum. The data were collected by the CMS detector in proton-proton collisions at the LHC and correspond to an integrated luminosity of 19.7 fb$^{-1}$ at a centre-of-mass energy of 8 TeV. The number of observed events is found to be consistent with the standard model prediction. Limits are placed on the DM-nucleon scattering cross section as a function of the DM particle mass for spin-dependent and spin-independent interactions. Limits are also placed on the scale parameter $M_\mathrm{D}$ in the ADD model of large extra dimensions, and on the unparticle model parameter $\Lambda_\mathrm{U}$. The constraints on ADD models and unparticles are the most stringent limits in this channel and those on the DM-nucleon scattering cross section are an improvement over previous collider results.