No Arabic abstract
Inclusive Higgs boson pair production through the mechanism of gauge boson fusion e^{+} e^{-} -> V* V* -> h h + X (V=W,Z) in the general Two-Higgs-Doublet Model (2HDM), with h=h^0,H^0,A^0,H^{pm}, is analyzed at order alpha^4_{ew} in the linear colliders ILC and CLIC. This kind of processes is highly sensitive to the trilinear Higgs (3H) boson self-interactions and hence can be a true keystone in the reconstruction of the Higgs potential. For example, in the ILC at 1 TeV, the most favorable scenarios yield cross-sections up to roughly 1 pb, thus entailing 10^5 events per 100 fb^{-1} of integrated luminosity, whilst remaining fully consistent with the perturbativity and unitarity bounds on the 3H couplings, the electroweak precision data and the constraints from BR(b->sgamma). Comparing with other competing mechanisms, we conclude that the Higgs boson-pair events could be the dominant signature for Higgs-boson production in the TeV-class linear colliders for a wide region of the 2HDM parameter space, with no counterpart in the Minimal Supersymmetric Standard Model. Owing to the extremely clean environment of these colliders, inclusive 2H events should allow a comfortable tagging and might therefore open privileged new vistas into the structure of the Higgs potential.
We analyse the loop induced production of Higgs boson pairs at future high--energy $e^+e^-$ colliders, both in the Standard Model and in its minimal supersymmetric extension. The cross sections for Standard Model Higgs pair production through $W/Z$ boson loops, $ee ra H^0 H^0$, are rather small but the process could be visible for high enough luminosities, especially if longitudinal polarization is made available. In the Minimal Supersymmetric Standard Model, the corresponding processes of CP--even or CP--odd Higgs boson pair production, $ee ra hh, HH, Hh$ and $ee ra AA$ have smaller cross sections, in general. The additional contributions from chargino/neutralino and slepton loops are at the level of a few percent in most of the supersymmetric parameter space.
We study the potential of hadron colliders in the search for the pair production of neutral Higgs bosons in the framework of the Minimal Supersymmetric Standard Model. We perform a detailed signal and background analysis, working out efficient kinematical cuts for the extraction of the signal. The important role of squark loop contributions to the signal is re--emphasized. If the signal is sufficiently enhanced by these contributions, it could even be observable at the next run of the upgraded Tevatron collider in the near future. At the LHC the pair production of light and heavy Higgs bosons might be detectable simultaneously.
I report on a calculation of the inclusive Higgs boson production cross section at hadron colliders at next-to-next-to-leading order in QCD. The result is computed as an expansion about the threshold region. By continuing the expansion to very high order, we map the result onto basis functions and obtain the result in closed analytic form.
We study the potential of the TESLA linear collider operated at a center-of-mass energy of 500 to 1000 GeV for the measurement of the neutral Higgs boson properties within the framework of the MSSM. The process of associated Higgs boson production with subsequent decays of Higgs bosons into b-quark and tau-lepton pairs is considered. An integrated luminosity of 500 fb^{-1} is assumed at each energy. The Higgs boson masses and production cross sections are measured by reconstructing the bbbb and bbtautau final states. The precision of these measurements is evaluated in dependence of the Higgs boson masses. Under the assumed experimental conditions a statistical accuracy ranging from 0.1 to 1.0 GeV is achievable on the Higgs boson mass. The topological cross section sigma(e+e- -> HA -> bbbb) can be determined with the relative precision of 1.5 - 6.6 % and cross sections sigma(e+e- -> HA -> bb tautau) and sigma(e+e- -> HA -> tautau bb) with precision of 4 - 30 %. Constraints on the Higgs boson widths can be set exploiting bbtautau channel. The 5sigma discovery limit corresponds to the Higgs mass of around 385 GeV for the degenerate Higgs boson masses in the HA -> bbbb channel at sqrts = 800 GeV with integrated luminosity of 500 fb^{-1}. The potential of the Higgs mass determination for the benchmark point SPS 1a for the process e+e- -> HA -> bbbb at sqrt{s} = 1 TeV and luminosity 1000 fb^{-1} is investigated.
We revisit the production of a single Higgs boson from direct gamma gamma -scattering at a photon collider. We compute the total cross section sigma(gamma gamma to h) (for h=h0, H0, A0), and the strength of the effective g_{h gamma gamma} coupling normalized to the Standard Model (SM), for both the general Two-Higgs-Doublet Model (2HDM) and the Minimal Supersymmetric Standard Model (MSSM). In both cases the predicted production rates for the CP-even (odd) states render up to 10^4 (10^3) events per 500 invfb of integrated luminosity, in full consistency with all the theoretical and phenomenological constraints. Depending on the channel the maximum rates can be larger or smaller than the SM expectations, but in most of the parameter space they should be well measurable. We analyze how these departures depend on the dynamics underlying each of the models, supersymmetric and non-supersymmetric, and highlight the possible distinctive phenomenological signatures. We demonstrate that this process could be extremely helpful to discern non-supersymmetric Higgs bosons from supersymmetric ones. Furthermore, in the MSSM case, we show that gammagamma-physics could decisively help to overcome the serious impasse afflicting Higgs boson physics at the infamous LHC wedge.