In the Higgs Triplet Model and the neutrinophilic Two-Higgs-Doublet Model the observed neutrinos obtain mass from a vacuum expectation value which is much smaller than the vacuum expectation value of the Higgs boson in the Standard Model. Both models
contain a singly charged Higgs boson (H^-) whose Yukawa coupling is directly related to the neutrino mass (i.e. a neutrinophilic charged Higgs). The partial decay widths of H^- into a charged lepton and a neutrino (H^- to l^- nu) depend identically on the neutrino masses and mixings in the two models. We quantify the impact of the recent measurement of sin^2(2theta_{13}), which plays a crucial role in determining the magnitude of the branching ratio of H^- to e^- nu for the case of a normal neutrino mass ordering if the lightest neutrino mass m_0 < 10^{-3} eV. We also discuss the sizeable dependence of H^- to mu^- nu and H^- to tau^- nu on sin^2(theta_{23}), which would enable information to be obtained on sin^2(theta_{23}) and the sign of Delta m^2_{31} if these decays are measured. Such information would help neutrino oscillation experiments to determine the CP-violating phase delta.
While the properties of the 125 GeV Higgs boson-like particle observed by the ATLAS and CMS collaborations are largely compatible with those predicted for the Standard Model state, significant deviations are present in some cases. We, therefore, test
the viability of a Beyond the Standard Model scenario based on Supersymmetry, the CP-violating Next-to-Minimal Supersymmetric Standard Model, against the corresponding experimental observations. Namely, we identify possible model configurations in which one of its Higgs bosons is consistent with the LHC observation and evaluate the role of the explicit complex phases in both the mass and diphoton decay of such a Higgs boson. Through a detailed analysis of some benchmark points corresponding to each of these configurations, we highlight the impact of the CP-violating phases on the model predictions compared to the CP-conserving case.
We study the effect of explicit CP violation in the Higgs sectors of the MSSM in the di-photon decay of the lightest CP-mixed Higgs state. Further it is shown that the gluon fusion production mechanism along with the di-photon decay enhances CP-viola
ting effects for a large set of suitably chosen parameter values.
At the Large Hadron Collider, we prove the feasibility to detect pair production of the lightest CP-even Higgs boson h of a Type II 2-Higgs Doublet Model through the process q bar q --> Vhh (Higgs-strahlung, V=W+-,Z), in presence of two h --> b bar b
decays. We also show that, through such production and decay channels, one has direct access to the following Higgs self-couplings, thus enabling one to distinguish between a standard and the Supersymmetric version of the above model: lambda_(Hhh) -- which constrains the form of the Higgs potential -- as well as lambda_(W+- H+- h) and lambda_(Z A h) -- which are required by gauge invariance. Unfortunately, such claims cannot be extended to the Minimal Supersymmetric Standard Model, where the extraction of the same signals is impossible.
We present the one-loop corrections originating from Quantum Chromo-Dynamics (QCD) and Electro-Weak (EW) interactions of Supersymmetric (SUSY) origin within the Minimal Supersymmetric Standard Model (MSSM) to the single-top processes bq -> tq and qba
r q -> tbar b. We illustrate their impact onto top quark observables accessible at the Large Hadron Collider (LHC) in the t+jet final state, such as total cross section, several differential distributions and left-right plus forward-backward asymmetries. We find that in many instances these effects can be observable for planned LHC energies and luminosities, quite large as well as rather sensitive to several MSSM parameters.
We describe the impact of the full one-loop electroweak terms of O(alpha_s alpha_EM^3) entering the electron-positron into three-jet cross-section from sqrt(s)=M_Z to TeV scale energies. We include both factorisable and non-factorisable virtual corre
ctions and photon bremsstrahlung. Their importance for the measurement of alpha_S from jet rates and shape variables is explained qualitatively and illustrated quantitatively, also in presence of b-tagging.
We describe the impact of the full one-loop EW terms of O(alpha_s alpha_EM^3) entering the electron-positron into three-jet cross-section from sqrt{s}=M_Z to TeV scale energies. We include both factorisable and non-factorisable virtual corrections, p
hoton bremsstrahlung but not the real emission of W and Z bosons. Their importance for the measurement of alpha_S from jet rates and shape variables is explained qualitatively and illustrated quantitatively.
We compute the full one-loop Electro-Weak (EW) contributions of O(alpha_S alpha_EM^3) entering the electron-positron into a quark-antiquark pair plus one gluon cross section at the Z peak and LC energies in presence of polarisation of the initial sta
te and by retaining the event orientation of the final state. We include both factorisable and non-factorisable virtual corrections, photon bremsstrahlung but not the real emission of W^pm and Z bosons. Their importance for the final state orientation is illustrated for beam polarisation setups achieved at SLC and foreseen at ILC and CLIC.
The production of the lightest Higgs boson, $h^0$, in association with the lightest stop, $tilde{t}_{1}$, in the Minimal Supersymmetric Standard Model, is an interesting channel, as its cross section can be higher than Higgs production in association
with top quarks. Furthermore, the $tilde{t}_{1}tilde{t}^{*}_{1}h^{0}$ production rate is highly dependent on various Supersymmetric parameters. The mass, mixings, couplings and production cross sections relevant to the $tilde{t}_{1}tilde{t}^{*}_{1}h^{0}$ channel have been studied in the past. Here, we complement these analyses by performing a thorough decay study. We conclude that there is some scope for extracting this channel at the Large Hadron Collider, for suitable combinations of the Supersymmetric parameters, in several different decay channels of both the stop quarks and Higgs boson, the most numerically promising being the signature involving charm decays of the stops and bottom decay of the Higgs. This, in fact, remains true in the Supergravity inspired Minimal Supersymmetric Standard Model.
We report on detailed Monte Carlo comparisons of selection variables to separate tbH+ signal events from the Standard Model ttbar background using an Iterative Discriminant Analysis (IDA) method. While kinematic differences exist between the two proc
esses whenever m(H+).ne.m(W+), the exploration of the spin difference between the charged Higgs and the W+ gauge boson becomes crucial in the particularly challenging case of near degeneracy of the charged Higgs boson mass with the W+ mass. The TAUOLA package is used to decay the tau leptons emerging from the charged Higgs and W+ boson decays taking the spin difference properly into account. We demonstrate that, even if the individual selection variables have limited discriminant power, the IDA method achieves a significant separation between the expected signal and background. For both Tevatron and LHC energies, the impact of the spin effects and H+ mass on the separation of signal and background has been studied quantitatively. The effect of a hard transverse momentum cut to remove QCD background has been studied and it is found that the spin effects remain important. The separation is expressed in purity versus efficiency curves. The study is performed for charged Higgs boson masses between the W+ mass and near the top mass.
