Download or read book Observation of Standard Model Higgs Boson Decays to Tau Leptons and a Search for Dark Matter with the CMS Detector at the LHC written by Laura Margaret Dodd and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the standard model (SM) Higgs boson which decays to a pair of [tau] leptons is presented in this thesis using 35.9 f b−1 of 13 TeV data collected in 2016 by the CMS detector at CERN. The final states considered require that (1) one [tau] lepton decays leptonically while the other decays hadronically ([mu][tau]h or e[tau]h), (2) both taus decay hadronically ([tau]h[tau]h) or (3) one tau lepton decays to an electron while the other decays to a muon (e[mu]). This thesis specifically focuses on the details of the semi-hadronic decay channels ([mu][tau]h and e[tau]h), and presents the results of all channels combined. The signal strength, [mu], relative to the expectation for the SM Higgs boson is measured to be [mu] = 1.09+0.27−0.24. An excess is observed (expected) corresponding to 4.9 (4.7) [sigma] using 2016 data. The observed (expected) significance reaches 5.9 (5.9) [sigma] when combined with 7 and 8 TeV data collected at CMS. Subsequently following the SM search, a search for dark matter (DM) is presented and interpreted in two simplified Higgs-portal models: a baryonic dark matter model and a two Higgs-doublet model. In this thesis, the Higgs boson is required to decay to an opposite- sign tau pair. The tau pair final states considered are e[tau]h, [mu][tau]h, and [tau]h[tau]h. The expected 95% confidence level upper limits are produced and compared with the observed limit. No significant deviations beyond the SM prediction are observed.