Elementary Particles and Fields and String Theory Commons^™

Search For New Physics In Rare Higgs Boson Decays With The Cms Detector At The Large Hadron Collider, Himal Acharya

Doctoral Dissertations

A new boson with a mass of 125 GeV was discovered at the large hadron collider (LHC) in July 2012. The properties of this particle are so far consistent with the standard model (SM) expectation. Differences in the Higgs boson decay rates and predicted by the SM might indicate the presence of new particles and forces between them. Particularly, rare exclusive decays of the Higgs boson are a promising laboratory to study physics beyond the standard model. Searches for decays of the Higgs boson into a Z boson and a J/ψ meson or into pairs of J/ψ or Υ mesons …

Measurement Of The Cross Section Of Top Quark Pairs Produced In Association With A Photon In Lepton + Jets Events At √S = 13 Tev With Full Runii Cms Data, Nabin Poudyal

Wayne State University Dissertations

The inclusive production cross section of top quark pairs in association with a photon is measured in proton-proton collisions at the LHC with 13 TeV energy using the full RunII data collected by CMS in 2016, 2017, and 2018 with a total corresponding integrated luminosity of 137 fb −1 . The relative fraction of ttγ events normalized to inclusive tt production is measured. The cross section measurement provides important information about the electromagnetic coupling of the standard model top quark and is sensitive to physics beyond the standard model. The analysis is carried out in the in semileptonic decay channel …

Correction To Luminosity Measurement For The Pixel Luminosity Telescope At Cms, Krishna Thapa

Masters Theses

The search for and detailed study of new particles and forces with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) of CERN is fundamentally dependent on the precise measurement of the rate at which proton-proton collisions produce any particles, the so-called luminosity. Therefore, a new detector, the Pixel Luminosity Telescope (PLT), dedicated to measure the luminosity at high precision was added to the CMS experiment in 2015. It measures the inclusive charged particle production from each collision of proton bunches in the LHC. Additional charged particles which are observed by the instrument but produced from sources …

The Cms Pixel Luminosity Telescope Browser Interface, Mark Miller Foerster

Masters Theses

The search for and detailed study of new particles and forces with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) of CERN is fundamentally dependent on the precise measurement of the rate at which proton-proton collisions produce any particles, the so-called luminosity. For the discovery of the Higgs candidate in 2012 the relative precision of this quantity was about 2.5%. To be able to observe deviations from Standard Model predictions for decay rates of this particle and others which can hint to new phenomena the targeted luminosity uncertainty is about 1%. Therefore, a new device, the …

Search For Contact Interactions Using The Dimuon Mass Spectrum In P-P Collisions At Sqrt(S) = 8 Tev At Cms, Chamath Kottachchi

Wayne State University Dissertations

The mass hierarchy problem associated with the standard model suggests that there might be more fundamental particles in nature. If quarks and leptons have substructures, known as preons, the manifestation of compositeness can be a four-fermion contact interaction. The experimental signal for contact interactions is a non-resonant enhancement of the number of events in the high-mass region of the dimuon mass spectrum. This dissertation describes a detailed search strategy for contact interactions using the Compact Muon Solenoid experiment. The dimuon mass spectrum above 300 GeV has been studied using the data collected in 2012 at sqrt(s) = 8 TeV corresponding …

Measurement Of The Prompt Double J/Psi Production Cross Section In Pp Collisions At Sqrt(S) = 7 Tev, Andrew David York

Doctoral Dissertations

The simultaneous production of two J/psi mesons has been significantly observed in proton-proton collisions at a center-of-mass energy of 7 TeV with the CMS detector. The two J/psi mesons are fully reconstructed in their decay to muons. The signal yield is extracted with an extended maximum likelihood fit based on four event variables. A method was developed to correct for detector acceptances and efficiencies based on the measured momenta of the J/psi and their decay muons to maintain the least model dependence possible.

The measurement is performed in an acceptance region defined by the individual J/psi transverse momentum and rapidity. …

Measurement Of Production And Decay Properties Of Bs Mesons Decaying Into J/Psi Phi With The Cms Detector At The Lhc, Giordano Cerizza

Doctoral Dissertations

The production of hadrons containing b-quarks has been measured in proton anti-proton collisions up to center-of-massenergies of 1.96 TeV at the Tevatron. Information at lower energy is provided by electron-positron collision experiments.The underlying theory of hadronic interactions is tuned to those data but cannot reliably predict reaction rates from first principlesfor higher energies. Therefore, it is important to test the extrapolations and optimize model parameters for the new energy regime at the LHC. The b-hadrons from proton-proton collisions are a major source of background in searches for the Higgs boson andother heavy not-yet-discovered particles. Hence, it is important to quantify …