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Register a new userSupersymmetric Higgses beyond the MSSM: An update with flavour and Dark Matter constraints
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Guillaume Drieu La Rochelle Mr
Publication date
2012
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English
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Spurred by the discovery of a boson resonance at the LHC as the result of the search for the Standard Model Higgs, we pursue our investigation of the properties and signatures of Higgses in an effective supersymmetric scenario that goes beyond the usual MSSM. Such scenarios were first introduced to alleviate the naturalness problem of the MSSM Higgs and are found to have a very rich phenomenology that allows departures from the Standard Model in the production rate of the Higgs in many of the search channels. We now include the constraints from flavour observables in particular the rare decays b-> s gamma and Bs -> mu+ mu- including the recent measurement from LHCb. We also address the issue of Dark Matter and its impact on Higgs physics. In particular, we incorporate the latest data from XENON100 on the spin independent direct detection rates. These turn out to be powerful constraints, especially if one also imposes that the observed thermal relic density is obtained. We also study models with a low abundance that can more easily evade the direct detection rates. We study the impact of the flavour and Dark Matter observables on the production rates of the Higgs at the LHC, and their correlations in the diphoton, diphoton+jets and 4 leptons. We also comment on the other channels.
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The experiments at the Large Hadron Collider (LHC) have pushed the limits on masses of supersymmetric particles beyond the $sim$TeV scale. This compromises naturalness of the simplest supersymmetric extension of the Standard Model, the minimal supersymmetric Standard Model (MSSM). In this paper we advocate that perhaps the current experimental data are actually hinting towards the physics beyond MSSM. To illustrate this, we treat MSSM as a low energy limit of a more fundamental yet unspecified theory at a scale $Lambda$, and compute the fine-tuning measure $Delta$ for generic boundary conditions on soft SUSY breaking parameters and various cut-off scales. As a general trend we observe reduction in fine-tuning together with lowering $Lambda$. In particular, perfectly natural [$Delta lesssim mathcal{O}(10)$] theories with a multi-TeV spectrum of supersymmetric particles and consistent with all current observations can be obtained for $Lambda sim mathcal{O}(100)$TeV. The lowering of the fine-tuning for large cut-off scales can also be observed in theories exhibiting special quasi-fixed point behaviours of parameters. Our observations call for a more throughout exploration of possible alternative ultraviolet completions of MSSM.
As experimental searches for WIMP dark matter continue to yield null results, models beyond the WIMP paradigm have proliferated in order to elude ever improving observational constraints, among them that of sub-GeV dark matter mediated by a massive vector portal (a dark photon) associated with a new dark $U(1)$ gauge symmetry. It has been previously noted that for a significant range of the parameter space of this class of models, the annihilation of dark matter particles into a pair of dark photons can dominate the freeze-out process even when this process is kinematically forbidden for dark matter at rest -- this is known as the forbidden dark matter (FDM) regime. Prior studies of this regime, however, assume that any dark Higgs associated with breaking the dark $U(1)$ and imparting mass to the dark photon is decoupled from the dark matter and as such plays no role in the freeze-out process. In this paper, we explore the effects of a dark Higgs on sub-GeV dark matter phenomenology in this FDM regime by considering the simplest possible construction in which there exist non-trivial dark matter-dark Higgs couplings: a model with a single complex scalar DM candidate coupled directly to the dark Higgs field. We find that for a wide range of parameter space, the dark Higgs can alter the resulting relic abundance by many orders of magnitude, and that this effect can remain significant even for a small dark matter-dark Higgs coupling constant. Considering measurements from direct detection and measurements of the CMB, we further find that points in this models parameter space which recreate the appropriate dark matter relic abundance suffer only mild constraints from other sources at present, but may become accessible in near-future direct detection experiments.
The searches for heavy Higgs bosons and supersymmetric (SUSY) particles at the LHC have left the minimal supersymmetric standard model (MSSM) with an unusual spectrum of SUSY particles, namely, all squarks are beyond a few TeV while the Higgs bosons other than the one observed at 125 GeV could be relatively light. In light of this, we study a scenario characterized by two scales: the SUSY breaking scale or the squark-mass scale $(M_S)$ and the heavy Higgs-boson mass scale $(M_A)$.We perform a survey of the MSSM parameter space with $M_S < 10^{10}$ GeV and $M_A < 10^4$ GeV such that the lightest Higgs boson mass is within the range of the observed Higgs boson as well as satisfying a number of constraints. The set of constraints include the invisible decay width of the $Z$ boson and that of the Higgs boson, the chargino-mass limit, dark matter relic abundance from Planck, the spin-independent cross section of direct detection by LUX, and gamma-ray flux from dwarf spheroidal galaxies and gamma-ray line constraints measured by Fermi LAT. Survived regions of parameter space feature the dark matter with correct relic abundance, which is achieved through either coannihilation with charginos, $A/H$ funnels, or both. We show that future measurements, e.g., XENON1T and LZ, of spin-independent cross sections can further squeeze the parameter space.
Light neutralino dark matter can be achieved in the Minimal Supersymmetric Standard Model if staus are rather light, with mass around 100 GeV. We perform a detailed analysis of the relevant supersymmetric parameter space, including also the possibility of light selectons and smuons, and of light higgsino- or wino-like charginos. In addition to the latest limits from direct and indirect detection of dark matter, ATLAS and CMS constraints on electroweak-inos and on sleptons are taken into account using a simplified models framework. Measurements of the properties of the Higgs boson at 125 GeV, which constrain amongst others the invisible decay of the Higgs boson into a pair of neutralinos, are also implemented in the analysis. We show that viable neutralino dark matter can be achieved for masses as low as 15 GeV. In this case, light charginos close to the LEP bound are required in addition to light right-chiral staus. Significant deviations are observed in the couplings of the 125 GeV Higgs boson. These constitute a promising way to probe the light neutralino dark matter scenario in the next run of the LHC.
We have recently examined a large number of points in the parameter space of the phenomenological MSSM, the 19-dimensional parameter space of the CP-conserving MSSM with Minimal Flavor Violation. We determined whether each of these points satisfied existing experimental and theoretical constraints. This analysis provides insight into general features of the MSSM without reference to a particular SUSY breaking scenario or any other assumptions at the GUT scale. This study opens up new possibilities for SUSY phenomenology both in colliders and in astrophysical experiments. Here we shall discuss the implications of this analysis relevant to the study of dark matter.
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