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Search for Dark Matter in Final States Containing Semi-visible Jets from Proton-proton Collisions at [square Root]s

2022
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Release : 2022
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Book Synopsis Search for Dark Matter in Final States Containing Semi-visible Jets from Proton-proton Collisions at [square Root]s by : Colin Terrence Fallon

Download or read book Search for Dark Matter in Final States Containing Semi-visible Jets from Proton-proton Collisions at [square Root]s written by Colin Terrence Fallon. This book was released on 2022. Available in PDF, EPUB and Kindle. Book excerpt: "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.

Searching for Dark Matter with the CMS Detector in Proton-proton Collisions Containing a Single High-pT Photon and Large E^miss/t

2019
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Release : 2019
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Book Synopsis Searching for Dark Matter with the CMS Detector in Proton-proton Collisions Containing a Single High-pT Photon and Large E^miss/t by : Brandon Leigh Allen

Download or read book 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. This book was released on 2019. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Search for Dark Matter with ATLAS

2018-05-31 Science
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Release : 2018-05-31
Genre : Science
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Book Rating : 518/5 ( reviews)

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Book Synopsis Search for Dark Matter with ATLAS by : Ruth Pöttgen

Download or read book Search for Dark Matter with ATLAS written by Ruth Pöttgen. This book was released on 2018-05-31. Available in PDF, EPUB and Kindle. Book excerpt: 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 Proton-proton Collisions at 8 TeV with Missing Transverse Momentum and Vector Boson Tagged Jets

2016
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Release : 2016
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Book Synopsis Search for Dark Matter in Proton-proton Collisions at 8 TeV with Missing Transverse Momentum and Vector Boson Tagged Jets by :

Download or read book Search for Dark Matter in Proton-proton Collisions at 8 TeV with Missing Transverse Momentum and Vector Boson Tagged Jets written by . This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. This search uses jet substructure techniques to identify hadronically decaying vector bosons in both Lorentz-boosted and resolved scenarios. This analysis yields improvements of 80% in terms of excluded signal cross sections with respect to the previous CMS analysis using the same data set. No significant excess with respect to the standard model expectation is observed and limits are placed on the parameter space of the simplified models. Mediator masses between 80 and 400 GeV in the scalar and pseudoscalar models, and up to 1.5 TeV in the vector and axial vector models, are excluded.

Search for Dark Matter Particles in Proton-proton Collisions at $\sqrt{s}$

2016
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Release : 2016
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Book Synopsis Search for Dark Matter Particles in Proton-proton Collisions at $\sqrt{s}$ by :

Download or read book Search for Dark Matter Particles in Proton-proton Collisions at $\sqrt{s}$ written by . This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: 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.

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