arXiv subjects

Abdelhak Djouadi

Publications and source records attributed to Abdelhak Djouadi.

85 records · Page 5Linked to original sources

arXiv2001

Constraints on mSUGRA and SUSY particle production at future $e^+e^-$ linear colliders

We perform a complete analysis of the supersymmetric particle spectrum in the Minimal Supergravity (mSUGRA) model. We show that present constraints on the Higgs boson and superparticle masses from collider searches and precision measurements still allow for large regions of the mSUGRA parameter space where some sparticles as well as the heavier Higgs particles, are light enough to be produced at the next generation of $e^+e^-$ linear colliders. An important part of this parameter space remains even when we require that the density of the lightest neutralinos left over from the Big Bang falls in the range favored by current determinations of the Dark Matter density in the Universe.

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arXiv2001

Associated production of sfermions and gauginos at high-energy $e^+e^-$ colliders

In the context of the Minimal Supersymmetric extension of the Standard Model, we analyze the production at future high-energy $e^+e^-$ colliders of second and third generation scalar leptons as well as scalar quarks in association with neutralinos and charginos, $e^+e^-\to f\tilde{f}χ$. In the case of third generation squarks, we also discuss the associated production with gluinos. We show that the cross sections for some of these three-body final state processes could be significant enough to allow for the detection of scalar fermions with masses above the kinematical two--body threshold, $\sqrt{s}= 2m_{\tilde{f}}$. We then discuss, taking as a reference example the case of scalar muons, the production cross sections in various approximations and make a comparison with the full four-body production process, $e^+e^- \to f\bar{f} χχ$, in particular around the two-sfermion threshold.

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arXiv2001

Charged Higgs production from SUSY particle cascade decays at the LHC

We analyze the cascade decays of the scalar quarks and gluinos of the Minimal Supersymmetric extension of the Standard Model, which are abundantly produced at the Large Hadron Collider, into heavier charginos and neutralinos which then decay into the lighter ones and charged Higgs particles, and show that they can have substantial branching fractions. The production rates of these Higgs bosons can be much larger than those from the direct production mechanisms, in particular for intermediate values of the parameter $\tan β$, and could therefore allow for the detection of these particles. We also discuss charged Higgs boson production from direct two-body top and bottom squark decays as well as from two- and three-body gluino decays.

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arXiv2001

Probing the SUSY Higgs boson couplings to scalar leptons at high-energy $e^+e^-$ colliders

We discuss the production at $e^+e^-$ colliders of Higgs bosons in association with both the scalar leptons and the lightest neutralinos in the Minimal Supersymmetric extension of the Standard Model. While the rates for associated Higgs production with neutralinos and first/second generation sleptons are rather tiny, the cross section for the production of the lightest Higgs boson $h$ with scalar $τ$ lepton pairs can reach the femtobarn level at c.m. energies at and above 500 GeV in favorable regions of the parameter space, making this process potentially detectable at a high-luminosity $\ee$ collider, in particular in the $γγ$ option. This would provide a determination of the $h \tildeτ \tildeτ$ coupling and opens up the possibility of measuring the parameter $\tan β$.

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arXiv2000

QCD Corrections to Neutralino-Nucleon Scattering

We calculate the dominant loop corrections from both standard and supersymmetric QCD to the effective coupling of neutralinos to nucleons. The potentially largest corrections come from gluino-squark loop contributions to the Higgs boson couplings to quarks; these corrections also affect the leading spin-independent squark exchange contribution. Ordinary QCD corrections to the effective coupling of CP-even Higgs bosons to two gluons are also sizable. For large $\tanb$ values, i.e. in the region of parameter space probed by current and near-future direct Dark-Matter search experiments, the total corrections can exceed a factor of three.

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arXiv2000

SUSY-QCD Corrections to Higgs Boson Production at Hadron Colliders

We analyze the next-to-leading order SUSY-QCD corrections to the production of Higgs particles at hadron colliders in supersymmetric extensions of the Standard Model. Besides the standard QCD corrections due to gluon exchange and emission, genuine supersymmetric corrections due to the virtual exchange of squarks and gluinos are present. At both the Tevatron and the LHC, these corrections are found to be small in the Higgs-strahlung, Drell-Yan-like Higgs pair production and vector boson fusion processes.

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arXiv1999

Supersymmetry Effects on High-Precision Electroweak Observables

I summarise the virtual effects of the new particles predicted by supersymmetric extensions of the Standard Model on the high-precision electroweak observables measured at LEP/SLC, the Tevatron and CLEO. I will then discuss in some details the two-loop SUSY-QCD corrections to the $ρ$ parameter.

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arXiv1999

Higgs Particles at Linear e+e- Colliders: theoretical issues

I summarize the prospects for discovering and studying the properties of Higgs particles at future high-energy and high-luminosity $e^+e^-$ linear colliders. I will focus on the Higgs particle of the Standard Model and the Higgs bosons predicted by Supersymmetric theories.

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arXiv1999

Top Squark Effects on Higgs Boson Production and Decays at the LHC

In the Minimal Supersymmetric Standard Model, one of the scalar top quarks can be relatively light and its couplings to Higgs bosons strongly enhanced. I will discuss two consequences of this feature: 1) the effects of scalar top loops on the main production mechanism of the lightest Higgs boson at the LHC, the gluon-fusion mechanism $gg \to h$, and on the important decay channel into two photons $h \to γγ$; and 2) the production of the light Higgs particle in association with top-squark pairs at proton colliders, $pp \to \tilde{t}_1 \tilde{t}_1 h$.

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arXiv1997

Decays of the Higgs Bosons

We review the decay modes of the Standard Model Higgs boson and those of the neutral and charged Higgs particles of the Minimal Supersymmetric extension of the Standard Model. Special emphasis will be put on higher-order effects. [Talk given at the International Workshop on Quantum Effects in the MSSM. Barcelona, Spain, September 9-13, 1997.]

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arXiv1997

Higgs Boson Decays into Light Gravitinos

We study decays of the neutral and charged Higgs bosons of the minimal supersymmetric standard model into a very light gravitino and a neutralino or chargino. Present experimental constraints already imply that the lighter scalar Higgs boson can only have a very small branching ratio into this mode. However, if the gravitino mass is below $\sim 0.5$ eV, the heavier neutral and charged Higgs boson decays into a gravitino can be important or even dominant. We discuss the resulting signature for associate production of the heavy CP-even and the CP-odd states at future $e^+ e^-$ colliders, and comment on Higgs boson production at hadron colliders.

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arXiv1997

SUSY Higgs Boson Decays

I discuss the decay modes of the neutral and charged Higgs bosons in the minimal supersymmetric extension of the Standard Model. Special emphasis will be put on the the QCD corrections to the hadronic decay modes, the below threshold -three body- decays and the decays into supersymmetric particles, charginos, neutralinos and sfermions. A Fortran code calculating the various Higgs decay branching ratios is then briefly presented. [Talk given at the Ringberg Workshop The Higgs Puzzle, Ringberg Castle, Tegernsee, Germany, December 8-13 1996; to appear in the proceedings.]

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arXiv1996

Higgs Phenomenology: a short review

I briefly review the Higgs sector in the Standard Model and in its minimal supersymmetric extension. After summarizing the properties of the Higgs bosons, I will discuss the prospects for discovering these particles at the present colliders LEP2 and Tevatron, and at the next generation colliders LHC and a high--energy $e^+e^-$ linear collider. The possibilities of studying the properties of the Higgs bosons will be then summarized. [Short write-up of lectures given at the XXXVI Cracow School of Theoretical Physics, June 1996.]

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