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| Author | : Johannes Schulz |
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| Release | : 2018* |
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| Author | : Maximilian Knut Kiesel |
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| Release | : 2018 |
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| Release | : 2016 |
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A search for supersymmetry is performed in events with a single electron or muon in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were recorded by the CMS experiment at the LHC and correspond to an integrated luminosity of 2.3 inverse femtobarns. Several exclusive search regions are defined based on the number of jets and b-tagged jets, the scalar sum of the jet transverse momenta, and the scalar sum of the missing transverse momentum and the transverse momentum of the lepton. The observed event yields in data are consistent with the expected backgrounds from standard model processes. The results are interpreted using two simplified models of supersymmetric particle spectra, both of which describe gluino pair production. In the first model, each gluino decays via a three-body process to top quarks and a neutralino, which is associated with the observed missing transverse momentum in the event. Gluinos with masses up to 1.6 TeV are excluded for neutralino masses below 600 GeV. In the second model, each gluino decays via a three-body process to two light quarks and a chargino, which subsequently decays to a W boson and a neutralino. The mass of the chargino is taken to be midway between the gluino and neutralino masses. In this model, gluinos with masses below 1.4 TeV are excluded for neutralino masses below 700 GeV.
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| Total Pages | : 26 |
| Release | : 2016 |
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Our search for supersymmetry involving events with at least one photon, one electron or muon, and large missing transverse momentum has been performed by the CMS experiment. The data sample corresponds to an integrated luminosity of 19.7 fb-1 of pp collisions at √ s = 8 TeV, produced at the CERN LHC. No excess of events is observed beyond expectations from standard model processes. The result of the search is interpreted in the context of a general model of gauge-mediated supersymmetry breaking, where the charged and neutral winos are the next-to-lightest supersymmetric particles. Within this model, winos with a mass up to 360 GeV are excluded at the 95% confidence level. Also, two simplified models inspired by gauge-mediated supersymmetry breaking are also examined, and used to derive upper limits on the production cross sections of specific supersymmetric processes.
| Author | : Wing Howard To |
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| Total Pages | : 145 |
| Release | : 2013 |
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| ISBN | : 9781303052842 |
This thesis describes a search for supersymmetry (SUSY) at the Large Hadron Collider using data collected in Run 2011 at center of mass energy of 7 TeV by the Compact Muon Solenoid detector with an integrated luminosity of 4.98 $fb{-1}$. First, the Large Hadron Collider is briefly described along with the Compact Muon Solenoid detector. Second, the Standard Model of particle physics is described which leads to the motivations for supersymmetry and its description. Finally, a search for supersymmetry in events with a single lepton, 2 b-tagged jets and missing transverse energy is documented in detail. The results are used to predict the yields from the standard model in bins missing transverse energy (\met) and total transverse hadronic energy (HT). Limits are set using these results using a minimal supergravity SUSY model and simplified model spectra SUSY model.
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| Release | : 2016 |
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The results of a search for new physics in final states with photons and missing transverse energy are reported. The study is based on a sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 inverse femtobarns. Final states with two photons and significant missing transverse energy are used to search for supersymmetric particles in models of supersymmetry (SUSY) with general gauge-mediated (GGM) supersymmetry breaking. No excess is observed with respect to the standard model expectation, and the results are used to set limits on gluino pair production and squark pair production in the GGM SUSY framework. Gluino masses below 1.65 TeV and squark masses below 1.37 TeV are excluded at a 95% confidence level.
| Author | : Sam Daniel Mullin |
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| Total Pages | : 108 |
| Release | : 2016 |
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| ISBN | : 9781369146592 |
As successful as the Standard Model of particle physics has been it still has several major shortcomings which range from unanswered theoretical questions to a lack of any explanation for observed phenomena such as dark matter. One proposed theory for physics beyond the Standard Model which provides solutions for some of these issues is supersymmetry. This dissertation presents a search for supersymmetry using 2.3 fb -1 of proton-proton collision data. This data was collected at a center-of-mass energy of 13 TeV by the CMS detector at the LHC during 2015. This search focuses on top squark pair production where the produced stops both decay to an all hadronic final state. These decays are characterized by multiple jets and missing transverse momentum. A baseline search region is defined to be sensitive to signal processes which occur at rates many orders of magnitude lower than Standard Model processes. The sensitivity to various signal models is improved by dividing this baseline region into distinct categories. Events with an unreconstructed lepton from leptonic W boson decays constitute the primary background. There are also significant contributions from events where a Z boson decays invisibly to neutrinos especially in bins with higher missing transverse momentum. Events with multijet production where one jet has been severely mis-measured as well as those with a pair of top quarks and an invisibly decaying Z boson also have a small presence in the search region. The contributions from these processes to the search region is estimated using data control regions. No statistically significant deviations from the predicted background yields are observed. The results are interpreted in terms of exclusion limits using the Simplified Model Spectrum framework. Stop and neutralino masses are probed up to 780 GeV and 260 GeV respectively.
| Author | : De-Lin Xiong |
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| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : Physics |
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The mission of the CMS experiment at the LHC is to investigate and discover unknown physics in proton-proton collision events. This thesis presents a search for new physics in final states containing a photon and missing transverse momentum in proton-proton collisions at $\\\\sqrt{s}$ = 13 TeV, using the data collected in Run II (2016, 2017 and 2018) by the CMS experiment at the LHC, corresponding to an integrated luminosity of 137 $\\\\text{fb}^{-1}$. The standard model (SM) background in monophoton events can be a problem for sensitivity to new physics. The sensitivity to new physics scenarios can potentially be enhanced by other event properties. A new strategy that can potentially enhance the new physics sensitivity is the track multiplicity from the small mass splitting supersymmetry (SUSY). SUSY with small mass splittings indicates the masses difference between the SUSY particles is small ($\\\\tilde{q}, squark \\\\approx \\\\tilde{\\\\chi}$, dark matter particle). The track multiplicity in monophoton dataset with different bins of track $p_T$ will be studied, and compared with expectation.
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| Release | : 2015 |
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Two searches for physics beyond the standard model in events containing photons are presented. Our data sample used corresponds to an integrated luminosity of 19.7 fb-1 of proton-proton collisions at √s=8 TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. These results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at the 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles.
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| Total Pages | : 27 |
| Release | : 2016 |
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Results are presented from a search for supersymmetric particles in scenarios with a compressed mass spectrum. The data sample corresponds to 19.7 inverse femtobarns of proton-proton collisions recorded by the CMS experiment at √s = 8 TeV. The search targets top squark ($ ilde{t}$ pair production in scenarios with mass differences ?m = m($ ilde{t}$ – m($ ilde{i}$10) below the W-boson mass and with top-squark decays in the four-body mode ($ ilde{t}$ → blv$ ilde{i}$10), where the ($ ilde{i}$10) is assumed to be the lightest supersymmetric particle (LSP). The signature includes a high transverse momentum (pT) jet associated with initial-state radiation, one or two low-pT leptons, and significant missing transverse energy. The event yields observed in data are consistent with the expected background contributions from standard model processes. Limits are set on the cross section for top squark pair production as a function of the $ ilde{t}$ and LSP masses. Assuming a 100% branching fraction for the four-body decay mode, top-squark masses below 316 GeV are excluded for ?m = 25 GeV at 95% CL. Furthermore, the dilepton data are also interpreted under the assumption of chargino-neutralino production, with subsequent decays to sleptons or sneutrinos. Assuming a difference between the common $ ilde{i}$1+/$ ilde{i}$2+ mass and the LSP mass of 20 GeV and a ?-enriched decay scenario, masses in the range m( $ ilde{i}$1+)
