Search For Dark Matter Produced In Association With Monotop In The Fully Leptonic Channel In Proton Proton Collisions At 13 Tev With The Compact Muon Soleniod Experiment
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Search for Dark Matter Produced in Association with Monotop in the Fully Leptonic Channel in Proton-proton Collisions at 13 TeV with the Compact Muon Soleniod Experiment
A search for dark matter has been performed using the monotop model, with the dark matter signature in the form of large missing energy, presence of a b-tagged jet and an isolated lepton (electron and muon). The data analyzed in this analysis was collected from 2016-2018 amounting to an integrated luminosity of 137 $fb^{-1}$ from the proton-proton collisions at a center-of-mass energy ($\sqrt{s}$) of 13 TeV and upper exclusion limits on the mass of the dark matter mediator and the dark matter particle have been set at 95\% confidence level.
Search for Dark Matter Produced in Association with Top Quarks at the Compact Muon Solenoid
One of the fundamental open questions that cannot be currently explained by the Standard Model is the particle nature of dark matter. Though astrophysical observations provide indirect evidence of its existence, dark matter has not been directly measured so far. However, under certain assumptions, dark matter may be possible to produce and detect at high energy particle colliders like the LHC. This thesis presents a search for dark matter produced in association with top quarks in data collected by the CMS detector at the LHC, corresponding to 138 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV. Production of dark matter particles in association with both a single top quark and a pair of top quarks are considered. The search is performed in three separate channels depending on the number of leptons in the final state, which include the all hadronic, single lepton, and dileptonic final states. The primary strategy of the search is to look for an excess of events with respect to the background-only prediction in events with a large imbalance in the transverse momentum. The results are interpreted in the context of a simplified model in which either a scalar or pseudoscalar mediator couples to top quarks and to dark matter fermions. Future prospects for improving the search are also discussed.
Searching for Dark Matter with the CMS Detector in Proton-proton Collisions Containing a Single High-pT Photon and Large E^miss/t
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.