Squark Effects on Higgs Boson Production and Decay at the LHC

In the context of the Minimal Supersymmetric extension of the Standard Model, I discuss the effects of relatively light top and bottom scalar quarks on the main production mechanism of the lightest SUSY neutral Higgs boson $h$ at the LHC, the gluon--gluon fusion mechanism $gg \to h$, and on the most promising discovery channel, the two--photon decay mode $h \to \gamma \gamma$. In some areas of the parameter space, the top and bottom squark contributions can strongly reduce the production cross section times the branching ratio.Comment: 10 pages, latex, including 4 epsfig

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

Precision Higgs physics at a γγ\gamma \gamma collider

The loop induced coupling of an intermediate mass Higgs boson to two photons is a sensitive and unique measure for precision tests of physics beyond the Standard Model. In this work we summarize recent results on the expected precision of the partial $\Gamma (H \to \gamma \gamma)$ width at the $\gamma \gamma$ option of a future linear collider. Heavy particles do not decouple in general and differences between the SM and MSSM predictions or 2HD-models can differ in the percentile regime. Large non-Sudakov DL corrections need to be resummed and consistency requirements demand the use of the Sterman-Weinberg jet definition in order to avoid additional DL terms from three jet final states. We find that the well understood background process $\gamma \gamma \to q \bar{q}$ allows for a ${\mathcal O}$(2%) determination of $\Gamma (H \to \gamma \gamma)$ using conservative collider parameters. Recent improvements in the expected $\gamma \gamma$ luminosity suggest that the precision for the diphoton partial Higgs width can be further improved and is dominated by the error in BR($H \to b \bar{b}$) from the $e^\pm$ mode, which is presently estimated to be in the one percent regime.Comment: 6 pages, 3 epsfigures, Latex2e plus style files. Contribution to the International Workshop on High Energy Photon Photon Colliders at DESY, June 200

Detection of MSSM Higgs bosons from supersymmetric particle cascade decays at the LHC

In the context of the Minimal Supersymmetric extension of the Standard Model, we study the production of Higgs bosons at the Large Hadron Collider via cascade decays of scalar quarks and gluinos. We focus on the cascades involving heavier charginos and neutralinos, which decay into the neutral $h,A,H$ and charged $H^\pm$ bosons and lighter charginos and neutralinos, but we will also discuss direct decays of third--generation squarks into their lighter partners and Higgs bosons as well as top quark decays into $H^\pm$ bosons. We show that the production rates of relatively light Higgs bosons, M_\Phi \lsim 250 GeV, via these mechanisms can be rather large in some areas of the parameter space. Performing a fast detector simulation analysis that takes into account the signals and the various backgrounds, we show that the detection of the neutral Higgs bosons through their decays into $b\bar{b}$ pairs, and of the charged Higgs particles through the $\tau^\pm \nu$ signature, is possible at the LHC.Comment: 44 pages, latex, 17 figure

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

Tests of the Higgs properties at the next colliders

We discuss the tests of the fundamental properties of the Standard Model Higgs boson that can be performed in the next round of experiments.Comment: 8 pages, 4 figures. Talk presented at PLC2005 Warsaw and Kazimierz Lectures, 5/09-08/09 200