Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
We present the results of a search for Higgs bosons predicted in two-Higgs-doublet models, in the case where the Higgs bosons decay to tau lepton pairs, using 1.8 fb−1 of integrated luminosity of p{bar p} collisions recorded by the CDF II experiment at the Fermilab Tevatron. Studying the mass distribution in events where one or both tau leptons decay leptonically, no evidence for a Higgs boson signal is observed. The result is used to infer exclusion limits in the two-dimensional space of tan [beta] versus m{sub A} (the ratio of the vaccum expectation values of the two Higgs doublets and the mass of the pseudoscalar boson, respectively).
Author: Laura Margaret Dodd Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A search for the Higgs boson decaying to $\tau\tau$ using 7.8~fb$^{-1}$ of $p\bar{p}$ collisions at 1.96~TeV collected with CDF II detector is presented. The search is sensitive to four production mechanisms of the Higgs boson: ggH, WH, ZH and VBF. Modes where one tau decay leptonically, and another decay, hadronically, are considered. Two novel techniques are developed and used in the search. A Probabilistic Particle Flow Algorithm is used for energy measurements of the hadronic tau candidates. The signal is discriminated from backgrounds by the Missing Mass Calculator, which allows for full invariant mass reconstruction of $\tau\tau$ pair. The data are found to be consistent with the background only hypothesis. Therefore a 95\% confidence level upper limit on the Standard Model Higgs boson cross section was set. At $M_H$$=$120~GeV/$c^2$ observed limit is 14.9$\times\sigma_{SM}\times Br(\Htt)$.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Searches are presented for heavy scalar (H) and pseudoscalar (A) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of pp collisions collected with the CMS experiment at the LHC at a center-of-mass energy of √s=8 TeV and corresponding to an integrated luminosity of 19.5 fb-1. The decays H→hh and A→Zh, where h denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. Our search results are presented in terms of the H and A production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% C.L. cross section upper limits of approximately 7 pb on [sigma]B for H→hh and 2 pb for A→Zh. Furthermore, the results of a search for the rare decay of the top quark are presented; this results in a charm quark and an SM Higgs boson,t→ch, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% C.L. upper limit of 0.56% on B(t→ch).
Author: Francesca Shun-Ning Annarosa Ricci-Tam Publisher: ISBN: 9781339825892 Category : Languages : en Pages :
Book Description
In this dissertation, I present a search for non-standard decays of a Standard Model-like Higgs boson to pairs of light bosons, as predicted in models with extended Higgs sectors. In two Higgs doublet models, including the next-to-minimal supersymmetric standard model, the Higgs boson can decay into a pair of light pseudoscalars a. In this search, the gluon fusion, W and Z associated Higgs, and vector boson fusion production channels for the Higgs are all considered, and the decay H->aa with a->[tau][tau] is reconstructed from the tau decay products. The final state is characterized by one isolated high p[subscript]T muon plus at least one highly boosted pair of taus, of which one of the taus is required to decay to a muon.Using 19.7 fb−1 of 8 TeV center of mass pp collision data recorded by the Compact Muon Solenoid experiment at the Large Hadron Collider, a counting experiment is performed in a region of high di-tau invariant mass. We have found no excess of events above the Standard Model backgrounds, and the observed data is used to set upper limits on the branching ratio Br(H->aa)Br2(a->[tau][tau]). These results are equally applicable to decays of the SM-like Higgs boson to a pair of light scalars h.
Author: Andrey Elagin Publisher: ISBN: Category : Languages : en Pages :
Book Description
A search for the Higgs boson decaying to tau tau using 7.8 fb^-1 of pp collisions at 1.96 TeV collected with CDF II detector is presented. The search is sensitive to four production mechanisms of the Higgs boson: ggH, WH, ZH and VBF. Modes where one tau decay leptonically, and another decay, hadronically, are considered. Two novel techniques are developed and used in the search. A Probabilistic Particle Flow Algorithm is used for energy measurements of the hadronic tau candidates. The signal is discriminated from backgrounds by the Missing Mass Calculator, which allows for full invariant mass reconstruction of tau tau pair. The data are found to be consistent with the background only hypothesis. Therefore a 95% confidence level upper limit on the Standard Model Higgs boson cross section was set. At M_H=120 GeV/c^2 observed limit is 14.9 x sigma_SM x Br(H -> tau tau).
Author: Publisher: ISBN: Category : Languages : en Pages : 8
Book Description
We report on a search for the standard model Higgs boson decaying into pairs of? leptons in p{bar p} collisions produced by the Tevatron at √s = 1.96 TeV. The analyzed data sample was recorded by the CDFII detector and corresponds to an integrated luminosity of 6.0 fb−1. The search is performed in the final state with one? decaying leptonically and the second one identified through its semi-hadronic decay. Since no significant excess is observed, a 95% credibility level upper limit on the production cross section times branching ratio to the?? final state is set for hypothetical Higgs boson masses between 100 and 150 GeV/c2. For a Higgs boson of 120 GeV/c2 the observed (expected) limit is 14.6 (15.3) the predicted value.
Author: Publisher: ISBN: Category : Languages : en Pages : 260
Book Description
Two searches for the production of Higgs bosons decaying into [tau] and [mu] leptons, using data collected with the DØ detector at the Fermilab Tevatron p$\bar{p}$ collider, are presented. A search for the pair production of doubly charged Higgs bosons in the process q$\bar{q}$ 2!H++H--, where H ±± decays to [tau][tau], [mu][mu] or [tau][mu] lepton pairs, with an integrated luminosity of up to L = 7:0 fb-1, is presented. No signi cant excess of data over the expected SM background is observed and the results are used to set 95% C.L. limits on the pair production cross section of doubly charged Higgs bosons in the range 90
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
A search is presented for decays beyond the standard model of the 125 GeV Higgs bosons to a pair of light bosons, based on models with extended scalar sectors. Light boson masses between 5 and 62.5 GeV are probed in final states containing four tau leptons, two muons and two b quarks, or two muons and two tau leptons. The results are from data in proton-proton collisions corresponding to an integrated luminosity of 19.7 inverse-femtobarns, accumulated by the CMS experiment at the LHC at a center-of-mass energy of 8 TeV. No evidence for such exotic decays is found in the data. Upper limits are set on the product of the cross section and branching fraction for several signal processes. The results are also compared to predictions of two-Higgs-doublet models, including those with an additional scalar singlet.
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Author: Laura Margaret Dodd
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Author: Francesca Shun-Ning Annarosa Ricci-Tam
Author: Andrey Elagin
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Author: Mark Andrew Pickering
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