Showing papers by "Abdelhak Djouadi published in 2013"

The measurement of the Higgs self-coupling at the LHC: theoretical status

Abstract: Now that the Higgs boson has been observed by the ATLAS and CMS experiments at the LHC, the next important step would be to measure accurately its properties to establish the details of the electroweak symmetry breaking mechanism. Among the measurements which need to be performed, the determination of the Higgs self-coupling in processes where the Higgs boson is produced in pairs is of utmost importance. In this paper, we discuss the various processes which allow for the measurement of the trilinear Higgs coupling: double Higgs production in gluon fusion, vector boson fusion, double Higgs-strahlung and associated production with a top quark pair. We first evaluate the production cross sections for these processes at the LHC with center-of-mass energies ranging from the present $ \sqrt{s}=8 $ TeV to $ \sqrt{s}=100 $ TeV, and discuss their sensitivity to the trilinear Higgs coupling. We include the various higher order QCD radiative corrections, at next-to-leading order for gluon and vector boson fusion and at next-to-next-to-leading order for associated double Higgs production with a gauge boson. The theoretical uncertainties on these cross sections are estimated. Finally, we discuss the various channels which could allow for the detection of the double Higgs production signal at the LHC and estimate their potential to probe the trilinear Higgs coupling.

Direct detection of Higgs–portal dark matter at the LHC

Abstract: We consider the process in which a Higgs particle is produced in association with jets and show that monojet searches at the LHC already provide interesting constraints on the invisible decays of a 125 GeV Higgs boson. Using the latest monojet search performed by the CMS collaboration with 4.7 fb−1 of data, we set the 95 % confidence level limit on the invisible Higgs decay rate to be less than the total Higgs rate in the Standard Model. This limit could be significantly improved when more data at higher center of mass energies are collected, provided systematic errors on the Standard Model contribution to the monojet background can be reduced. In the context of Higgs portal models of dark matter, we then discuss how the LHC limits on the invisible Higgs branching fraction impose strong constraints on the dark matter scattering cross section on nucleons probed in direct detection experiments.

The MSSM Higgs sector at a high MSUSY: reopening the low tan β regime and heavy Higgs searches

Abstract: One of the main implications of the LHC discovery of a Higgs boson with a mass M h ≈ 126 GeV is that the scale of supersymmetry-breaking in the Minimal Supersymmetric Standard Model (MSSM) might be rather high, M S ≫ M Z . In this paper, we consider the high M S regime and study the spectrum of the extended Higgs sector of the MSSM, including the LHC constraints on the mass and the rates of the observed light h state. In particular, we show that in a simplified model that approximates the important radiative corrections, the unknown scale M S (and some other leading SUSY parameters) can be traded against the measured value of M h . One would be then essentially left with only two free parameters to describe the Higgs sector, tan β and the pseudoscalar Higgs mass M A , even at higher orders. The main phenomenological consequence of these high M S values is to reopen the low tan β region, tan β ≲ 3–5, which was for a long time buried under the LEP constraint on the lightest h mass when a low SUSY scale was assumed. We show that, in this case, the heavier MSSM neutral H/A and charged H ± states can be searched for in a variety of interesting final states such as decays into gauge and lighter Higgs bosons (in pairs on in mixed states) and decays into heavy top quarks. Examples of sensitivity on the [tan β, M A ] parameter space at the LHC in these channels are given.

The MSSM Higgs sector at a high $M_{SUSY}$: reopening the low tan$\beta$ regime and heavy Higgs searches

Abstract: One of the main implications of the LHC discovery of a Higgs boson with a mass $M_h \approx 126$ GeV is that the scale of supersymmetry-breaking in the Minimal Supersymmetric Standard Model (MSSM) might be rather high, $M_S \gg M_Z$. In this paper, we consider the high $M_S$ regime and study the spectrum of the extended Higgs sector of the MSSM, including the LHC constraints on the mass and the rates of the observed light $h$ state. In particular, we show that in a simplified model that approximates the important radiative corrections, the unknown scale $M_S$ (and some other leading SUSY parameters) can be traded against the measured value of $M_h$. One would be then essentially left with only two free parameters to describe the Higgs sector, tan$\beta$ and the pseudoscalar Higgs mass $M_A$, even at higher orders. The main phenomenological consequence of these high $M_S$ values is to reopen the low tan$\beta$ region, tan$\beta \lsim 3-5$, which was for a long time buried under the LEP constraint on the lightest $h$ mass when a low SUSY scale was assumed. We show that, in this case, the heavier MSSM neutral $H/A$ and charged $H^\pm$ states can be searched for in a variety of interesting final states such as decays into gauge and lighter Higgs bosons (in pairs on in mixed states) and decays into heavy top quarks. Examples of sensitivity on the $[tan\beta, M_A]$ parameter space at the LHC in these channels are given.

Implications of the Higgs discovery for the MSSM

Abstract: The implications of the discovery of the Higgs boson at the LHC with a mass of approximately 125 GeV are summarised in the context of the minimal supersymmetric extension of the Standard Model, the MSSM. Discussed are the implications from the measured mass and production/decay rates of the observed particle and from the constraints in the search for the heavier Higgs states at the LHC.

Implications of the Higgs discovery for SUSY

Abstract: The implications of the discovery of the Higgs boson at the LHC with a mass of approximately 125 GeV are discussed in the context of minimal supersymmetric extension of the Standard Model, the MSSM.

Implications of LHC Higgs and SUSY searches for MSSM

Abstract: The implications of the LHC SUSY searches as well as the discovery of a new bosonic state compatible with the lightest Higgs boson will be discussed in the context of constrained and general MSSM scenarios. Exploring the MSSM through the Higgs sector is an alternative and complementary path to direct searches, and tight constraints on the MSSM parameter space can be obtained.