Higgs particles at future hadron and electron-positron colliders

The prospects for discovering Higgs particles and studying their fundamental properties at future high-energy electron-positron and hadron colliders are reviewed. Both the Standard Model Higgs boson and the Higgs particles of its minimal supersymmetric extension are discussed. We update various results by taking into account the new value of the top quark mass obtained by the CDF Collaboration and by including radiative corrections some of which have been calculated only recently.Comment: 64 pages / 29 figures (available by mail from the author). invited review paper for Int.J.Mod.Phys.A, Latex styl

Lower Bounds on Charged Higgs Bosons from LEP and the TEVATRON

We point out that charged Higgs bosons can decay into final states different than $\tau^+ \nu_\tau$ and $c \bar{s}$, even when they are light enough to be produced at LEPII or at the Tevatron, through top-quark decays. These additional decay modes are overlooked in ongoing searches even though they alter the existing lower bounds on the mass of charged Higgs bosons that are present in supersymmetric and two Higgs doublets models.Comment: 9 pages, 4 figure

Two-loop scalar self-energies and pole masses in a general renormalizable theory with massless gauge bosons

I present the two-loop self-energy functions for scalar bosons in a general renormalizable theory, within the approximation that vector bosons are treated as massless or equivalently that gauge symmetries are unbroken. This enables the computation of the two-loop physical pole masses of scalar particles in that approximation. The calculations are done simultaneously in the mass-independent \bar{MS}, \bar{DR}, and \bar{DR}' renormalization schemes, and with arbitrary covariant gauge fixing. As an example, I present the two-loop SUSYQCD corrections to squark masses, which can increase the known one-loop results by of order one percent. More generally, it is now straightforward to implement all two-loop sfermion pole mass computations in supersymmetry using the results given here, neglecting only the electroweak vector boson masses compared to the superpartner masses in the two-loop parts.Comment: 16 pages, 4 figures. v2: typo in eq. (5.30) fixe

Two-Photon Decay Widths of Higgs Particles

Two--photon decays of Higgs bosons are important channels for the search of these particles in the intermediate mass range at the $pp$ colliders LHC and SSC. Dynamical aspects of the Higgs coupling to two photons can also be studied by means of the $\gamma \gamma$ fusion of Higgs particles at high--energy e$^+$e$^-$ linear colliders. Extending earlier analyses which had been restricted to the Standard Model, we present in this note the QCD radiative corrections to the $\gamma \gamma$ decay widths of scalar and pseudoscalar Higgs particles in multi--doublet extensions of the Higgs sector, as realized for instance in supersymmetric theories.Comment: 8pages + 3figures (not included, a hard copy is available from A.D. upon request), Prep. DESY 92-170 (to appear in Phys. Lett. B

The forward-backward asymmetry of top quark production at the Tevatron in warped extra dimensional models

The CDF and D0 experiments have reported on the measurement of the forward-backward asymmetry of top quark pair production at the Tevatron and the result is that it is more than 2 standard deviations above the predicted value in the Standard Model. This has to be added to the longstanding anomaly in the forward-backward asymmetry for bottom quark production at LEP which is 3 standard deviations different from the Standard Model value. The discrepancy in the bottom asymmetry can be accounted for by the contributions of Kaluza-Klein excitations of electroweak gauge bosons at LEP in warped extra dimensional models in which the fermions are localized differently along the extra dimension so that the gauge interactions of heavy third generation fermions are naturally different from that of light fermions. In this paper, we show that it is more difficult to elaborate a model generating a significant top asymmetry in a similar way -- through exchanges of Kaluza-Klein gluons at the Tevatron -- due to the indirect constraints originating from precision electroweak data.Comment: 4 pages, 1 figure, published versio