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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 Decaying to Two Displaced Muons Produced in Proton-proton Collisions at 13 TeV with the CMS Detector, and for Dark Photons Produced in Electron-positron Fixed-target Collisions at 500 MeV with the PADME Detector

2020
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Release : 2020
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Book Synopsis Search for Dark Matter Decaying to Two Displaced Muons Produced in Proton-proton Collisions at 13 TeV with the CMS Detector, and for Dark Photons Produced in Electron-positron Fixed-target Collisions at 500 MeV with the PADME Detector by : Andre Sterenberg Frankenthal

Download or read book Search for Dark Matter Decaying to Two Displaced Muons Produced in Proton-proton Collisions at 13 TeV with the CMS Detector, and for Dark Photons Produced in Electron-positron Fixed-target Collisions at 500 MeV with the PADME Detector written by Andre Sterenberg Frankenthal. This book was released on 2020. Available in PDF, EPUB and Kindle. Book excerpt: Two novel searches for dark matter using particle accelerators are presented. The first is a search for inelastically-coupled dark matter with the CMS detector at CERN, relying on 137 inverse femtobarns of proton-proton collision data collected at 13 TeV center-of-mass energy between 2016 and 2018. The search strategy exploits the striking signature expected of inelastic dark matter: a pair of displaced, soft, and narrow muons collimated with missing transverse momentum and recoiled off an initial-state radiation jet. This is the first search for inelastic dark matter at a hadron collider. The second experiment is PADME, a small-scale detector to search for dark photons located in Frascati, Italy. PADME seeks to detect the production of dark photons in positron-electron collisions with a stationary diamond target and a 500 MeV positron beam. The missing-mass technique employed in the experiment relies on constraining all four-momenta in the system except for the dark photon and looking for a bump in the resulting invariant mass distribution corresponding to the dark photon's mass. The projected sensitivity for both experiments is compared in the context of highlighting the need for a comprehensive experimental search program for dark matter. Both analyses expect first public results by the end of 2020.

Search for Dark Matter and Supersymmetry in the Single Photon Events with the ATLAS Detector

2015
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Release : 2015
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Book Synopsis Search for Dark Matter and Supersymmetry in the Single Photon Events with the ATLAS Detector by : Mengqing Wu

Download or read book Search for Dark Matter and Supersymmetry in the Single Photon Events with the ATLAS Detector written by Mengqing Wu. This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the search for new physics in the final state containing a single photon and missing transverse momentum. The analysis is performed on 20.3fb-1 of proton-proton collisions data at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the Large Hadron Collider. Given the good agreement of the data with the Standard Model pre- diction of such events, an upper limit to the visible cross section produced by new physics is derived. The observed limit at 95% confidence level is 3.64 fb.In this thesis, the results are also interpreted as limits in the parameter space of two new physics models. The first model is an effective field theory, inspired by Fermi-LAT results, in which dark matter particles couple to photons via a contact interaction vertex. Limits are set on the effective mass scale and depend on the postulated coupling constants. The limits set in this dark matter model provide an effective constraint in the parameter space of the theory compatible with the Fermi-LAT results. The second one is a simplified supersymmetric model describing squark pair production with their subsequent decay into a quark and a neutralino. The photon is emitted as initial or final state radiation and the spectrum is compressed, i.e. the mass difference between the squark and the neutralino is assumed to be small. Limits are set on the production cross-section; squark masses are excluded up to 250 GeV in the very compressed region. As the photon can be irradiated from the intermediate squark, this final state would eventually provide the possibility to probe the charge of the squark.A preliminary study has also been carried out to show the search sensitivity with 13 TeV data, which indicate that the limits presented in this thesis can already be improved by 10% with 5fb-1.

Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS

2016-09-29 Science
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Release : 2016-09-29
Genre : Science
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Book Synopsis Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS by : Yangyang Cheng

Download or read book Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS written by Yangyang Cheng. This book was released on 2016-09-29. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.

Search for Dark Matter with ATLAS

2016-06-29 Science
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Release : 2016-06-29
Genre : Science
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Book Rating : 458/5 ( 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 2016-06-29. 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.

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