Higgsino Dark Matter Research Articles

Higgsino dark matter in high-scale supersymmetry

We study a supersymmetric (SUSY) Standard Model in which a Higgsino is light enough to be dark matter, while the other SUSY particles are much heavier than the weak scale. We carefully treat the effects of heavy SUSY particles to the Higgsino nature, especially taking into account the renormalization effects due to the large hierarchy between the Higgsino and the SUSY breaking scales. Inelastic scattering of the Higgsino dark matter with a nucleus is studied, and the constraints on the scattering by the direct detection experiments are discussed. This gives an upper limit on the new physics scale. Bounds on the dark matter-nucleon elastic scattering, the electric dipole moments, and direct production of Higgsinos, on the other hand, give a lower limit. We show the current status on the limits and discuss the future prospects.

Neutralino and gravitino dark matter with low reheating temperature

Abstract We examine a scenario in which the reheating temperature T R after inflation is so low that it is comparable to, or lower than, the freeze out temperature of ordinary WIMPs. In this case the relic abundance of dark matter is reduced, thus relaxing the impact of the usually strong constraint coming from the requirement that the universe does not overclose. We first re-examine the dynamics of freezeout during reheating. Next we study the parameter space of the MSSM with ten free parameters, the Constrained MSSM and the singlino-dominated regions of the Next-to-MSSM. In each case we often find dramatic departures from the usually considered regime of high T R , with important implications for direct detection dark matter searches. In particular, in the MSSM we examine WIMP mass range up to about 5 TeV, and we find large regions of bino dark matter over the whole mass range, and of higgsino dark matter with mass over a similar range but starting from the ∼ 1 TeV value of the standard high T R scenario. We show that the prospects for bino detection strongly depend on T R , while the higgsino is for the most part detectable by future one-tonne detectors. The wino, which is excluded in the standard scenario, becomes allowed again if its mass is roughly above 3.5 TeV, and can also be partially detectable. In the CMSSM, the bino and higgsino mass ranges become much more constrained although detection prospects remain roughly similar. In the Next-to-MSSM we show that, at low enough T R wide ranges of singlino-dominated parameter space of the model become again cosmologically allowed, although detection prospects remain nearly hopeless. We also study the non-thermal contribution to the DM relic density from direct and cascade decays of the inflaton. Finally, in the framework of the MSSM we consider the case of a gravitino as dark matter. In this case we find strong bounds from overclosure and from Big Bang Nucleosynthesis, and derive lower limits on T R which depend on the gravitino mass and on the nature of the lightest ordinary superpartner.

Split Dirac supersymmetry: An ultraviolet completion of Higgsino dark matter

Motivated by the observation that the Higgs quartic coupling runs to zero at an intermediate scale, we propose a new framework for models of split supersymmetry, in which gauginos acquire intermediate scale Dirac masses of $\sim 10^{8-11}$ GeV. Scalar masses arise from one-loop finite contributions as well as direct gravity-mediated contributions. Like split supersymmetry, one Higgs doublet is fine-tuned to be light. The scale at which the Dirac gauginos are introduced to make the Higgs quartic zero is the same as is necessary for gauge coupling unification. Thus, gauge coupling unification persists (nontrivially, due to adjoint multiplets), though with a somewhat higher unification scale $\gtrsim 10^{17}$ GeV. The $\mu$-term is naturally at the weak scale, and provides an opportunity for experimental verification. We present two manifestations of Split Dirac Supersymmetry. In the "Pure Dirac" model, the lightest Higgsino must decay through R-parity violating couplings, leading to an array of interesting signals in colliders. In the "Hypercharge Impure" model, the bino acquires a Majorana mass that is one-loop suppressed compared with the Dirac gluino and wino. This leads to weak scale Higgsino dark matter whose overall mass scale, as well as the mass splitting between the neutral components, is naturally generated from the same UV dynamics. We outline the challenges to discovering pseudo-Dirac Higgsino dark matter in collider and dark matter detection experiments.

Nonthermal histories and implications for structure formation

We examine the evolution of cosmological perturbations in a non-thermal post-inflationary history with a late-time matter domination period prior to BBN. Such a cosmology could arise naturally in the well-motivated moduli scenario in the context of supersymmetry (SUSY) -- in particular in models of Split-SUSY. Sub-horizon dark matter perturbations grow linearly during the matter dominated phase before reheating and can lead to an enhancement in the growth of substructure on small scales, even in the presence of dark matter annihilations. This suggests that a new scale (the horizon size at reheating) could be important for determining the primordial matter power spectrum. However, we find that in many non-thermal models free-streaming effects or kinetic decoupling after reheating can completely erase the enhancement leading to small-scale structures. In particular, in the moduli scenario with wino or higgsino dark matter we find that the dark matter particles produced from moduli decays would thermalize with radiation and kinetically decouple below the reheating temperature. Thus, the growth of dark matter perturbations is not sustained, and the predictions for the matter power spectrum are similar to a standard thermal history. We comment on possible exceptions, but these appear difficult to realize within standard moduli scenarios. We conclude that although enhanced structure does not provide a new probe for investigating the cosmic dark ages within these models, it does suggest that non-thermal histories offer a robust alternative to a strictly thermal post-inflationary history.

What next for the CMSSM and the NUHM: improved prospects for superpartner and dark matter detection

We present an updated analysis of the CMSSM and the NUHM using the latest experimental data and numerical tools. We map out favored regions of Bayesian posterior probability in light of data from the LHC, flavor observables, the relic density and dark matter searches. We present some updated features with respect to our previous analyses: we include the effects of corrections to the light Higgs mass beyond the 2-loop order using FeynHiggs v2.10.0; we include in the likelihood the latest limits from direct searches for squarks and gluinos at ATLAS with ~20/fb; the latest constraints on the spin-independent scattering cross section of the neutralino from LUX are applied taking into account uncertainties in the nuclear form factors. We find that in the CMSSM the posterior distribution now tends to favor smaller values of Msusy than in the previous analyses. As a consequence, the statistical weight of the A-resonance region increases to about 30% of the total probability, with interesting new prospects for the 14 TeV run at the LHC. The most favored region, on the other hand, still features multi-TeV squarks and gluinos, and ~1TeV higgsino dark matter whose detection prospects by current and one-tonne detectors look very promising. The same region is predominant in the NUHM, although the A-resonance region is also present there as well as a new solution, of neutralino-stau coannihilation through the channel stau stau -> hh at very large \mu. We derive the expected sensitivity of the future CTA experiment to ~1 TeV higgsino dark matter for both models and show that the prospects for probing both models are realistically good. We comment on the complementarity of this search to planned direct detection one-tonne experiments.

Composite Higgsino

Several supersymmetric models in which there is a (partially) composite Higgs boson arising from (coupled to) a strong sector have been proposed. Such strong dynamics would help to cause the electroweak symmetry breaking naturally. In this paper, we focus on the compositeness of the Higgsinos in such models. We show that such a Higgsino compositeness can induce the characteristic decay branching fraction of the neutralinos. In such scenarios, the decay branching fraction of the second lightest neutral Higgsino into the lightest neutral Higgsino with photon can be large due to a dipole interaction. We also discuss the Higgsino dark matter feature. The annihilation cross section into gamma Z can be large.

Neutralino dark matter in gauge mediation after run I of LHC and LUX

Neutralino can be the dark matter candidate in the gauge-mediated supersymmetry breaking models if the conformal sequestered mechanism is assumed in the hidden sector. In this paper, we study this mechanism by using the current experimental results after the run I of LHC and LUX. By adding new Yukawa couplings between the messenger fields and Higgs fields, we find that this mechanism can predict a neutralino dark matter with correct relic density and a Higgs boson with mass around 125 GeV. All our survived points have some common features. First, the Higgs sector falls into the decoupling limit. So the properties of the light Higgs boson are similar to the predictions of the Standard Model one. Second, the correct EWSB hints a relatively small μ-term, which makes the lightest neutralino lighter than the lightest stau. So a bino–higgsino dark matter with correct relic density can be achieved. And the relatively small μ-term results in a small fine-tuning. Finally, this bino–higgsino dark matter can pass all current bounds, including both spin-independent and spin-dependent direct searches. The spin-independent cross section of our points can be examined by further experiments.

Low fine tuning in the MSSM with higgsino dark matter and unification constraints

We examine the issue of fine tuning in the MSSM with GUT-scale boundary conditions. We identify specific unification patterns and mass relations that can lead to a significant lowering of the fine tuning due to gauginos, scalars, and the \mu\ parameter, relative to the simplest unification conditions. We focus on a phenomenologically interesting region that is favored by the Higgs mass and the relic density where the dark matter is a nearly pure higgsino with mass given by \mu~1 TeV while the scalars and gauginos have masses in the multi-TeV regime. There, we find that the fine tuning can be reduced to the level of a few percent. Despite the gluino mass in the ballpark of 2 TeV, resulting mass spectra will be hard to explore at the LHC, but good prospects for detection come from dark matter direct detection experiments. Finally, we demonstrate with a specific example how the conditions and mass relations giving low fine tuning can originate in the context of supergravity and Grand Unified Theories.

SUSY dark matter in nonuniversal gaugino mass models

We discuss the SUSY dark matter phenomenology in some simple and predictive models of nonuniversal gaugino masses at the GUT scale. Assuming the gaugino masses to transform as a sum of singlet and a nonsinglet representation of the GUT group SU(5), one can evade the LEP constraints to access the bulk annihilation region of the bino dark matter relic density. Besides, with this assumption one can also have a mixed gaugino–higgsino dark matter, giving the right relic density over large parts of the parameter space. We consider the model predictions for LHC and dark matter experiments in both the cases. Finally we consider the AMSB model prediction of wino dark matter giving the right relic density for TeV scale wino mass. Assuming this wino dark matter mass to be at the first Sommerfeld resonance of ~ 4 TeV one can simultaneously reproduce the right relic density as well as the hard positron spectrum observed by the PAMELA experiment. -

Non-thermal Higgsino dark matter, heavy gravitino and 125 GeV Higgs boson in modulus/anomaly-mediated supersymmetric models

If the lightest supersymmetric particle (LSP) is Higgsino-like, the thermal relic density is lower than the observed dark matter content for a LSP mass in the sub-TeV region. We outline constraints arising from the Fermi Gamma-ray Telescope data and LSP production from gravitino decay that must be satisfied by a successful nonthermal Higgsino scenario. We show that in a generic class of models where anomaly- and modulus-mediated contributions to supersymmetry breaking are of comparable size, Higgsino arises as the only viable sub-TeV dark matter candidate if gravitinos are heavy enough to decay before the onset of big bang nucleosynthesis. The correct relic density can be obtained via modulus decay in these models. As an explicit example, we consider a modulus sector in effective field theory ($D=4$, $N=1$ supergravitiy arising from type IIB Kachru-Kallosh-Linde-Trivedi compactification). Within this class of mirage mediation models, heaviness of the gravitino forces a sub-TeV Higgsino LSP and gives a Higgs mass around 125 GeV. In this example, the constraints from direct detection experiments are also satisfied.

Fermiophobic Higgs boson and supersymmetry

If a light Higgs boson with mass 125 GeV is fermiophobic, or partially fermiophobic, then the MSSM is excluded. The minimal supersymmetric fermiophobic Higgs scenario can naturally be formulated in the context of the NMSSM that admits Z_3 discrete symmetries. In the fermiophobic NMSSM, the SUSY naturalness criteria are relaxed by a factor N_c y_t^4/g^4 \sim 25, removing the little hierarchy problem and allowing sparticle masses to be naturally of order 2--3 TeV. This scale motivates wino or higgsino dark matter. The SUSY flavour and CP problems as well as the constraints on sparticle and Higgs boson masses from b \to s\gamma, B_s \to \mu\mu\ and direct LHC searches are relaxed in fermiophobic NMSSM. The price to pay is that a new, yet unknown, mechanism must be introduced to generate fermion masses. We show that in the fermiophobic NMSSM the radiative Higgs boson branchings to \gamma\gamma, \gamma Z can be modified compared to the fermiophobic and ordinary standard model predictions, and fit present collider data better. Suppression of dark matter scattering off nuclei explains the absence of signal in XENON100.

Natural supersymmetry: LHC, dark matter and ILC searches

Particle physics models with Natural Supersymmetry are characterized by a superpotential parameter μ ∼ m h ∼ 125 GeV, while third generation squarks have mass $ _\sim^< $ 0.5–1.5 TeV. Gluinos should be lighter than several TeV so as not to destabilize the lighter squarks. First and second generation sfermions can be at the tens-of-TeV level which yields a decoupling solution to the SUSY flavor and CP problems. Adopting a top- down approach, we delineate the range of GUT scale SUSY model parameters which leads to a Natural SUSY mass spectrum. We find natural SUSY models to be tightly constrained by the b → sγ branching fraction measurement while it is also difficult but not impossible to accommodate a light Higgs scalar of mass ≃ 125 GeV. We present several benchmark points which are expandable to slopes and planes. Natural SUSY is difficult to see at LHC unless some third generation squarks are very light. The top- and bottom- squarks cascade decay mainly to higgsino-like charginos and neutralinos via numerous possibilities, leading to a rather complex set of signatures. Meanwhile, a linear e + e − collider operating at $ \sqrt {s} $ ∼ 0.25–0.5 TeV would be a higgsino factory and is essentially guaranteed a SUSY discovery of the low-lying charged and neutral higgsino states. Since thermal neutralino cold dark matter is underproduced, we conjecture that the incorporation of a Peccei-Quinn sector or light moduli into the theory will augment higgsino dark matter production, possibly together with an admixture of axions. We present rates for direct and indirect higgsino dark matter detection for the case where light higgsinos dominate the dark matter abundance.

Higgsino dark matter model consistent with galactic cosmic ray data and possibility of discovery at LHC-7

A solution to the PAMELA positron excess with Higgsino dark matter within extended supergravity grand unified (SUGRA) models is proposed. The models are compliant with the photon constraints recently set by Fermi-LAT and produce positron as well as antiproton fluxes consistent with the PAMELA experiment. The SUGRA models considered have an extended hidden sector with extra degrees of freedom which allow for a satisfaction of relic density consistent with WMAP. The Higgsino models are also consistent with the CDMS-II and XENON100 data and are discoverable at LHC-7 with 1 fb^(-1) of luminosity. The models are testable on several fronts.

Mixed higgsino dark matter from a large SU(2) gaugino mass

We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M2| from its unified value results in a smaller value of ?mHu2 at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of ?2 vis ? vis models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M2| DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left- and right- sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where m 2350?2750 GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + ?+??+ETmiss events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.

Supersymmetry without a light Higgs boson

Motivated by the absence, so far, of any direct signal of conventional low-energy supersymmetry, we explore the consequences of making the lightest Higgs boson in supersymmetry relatively heavy, up to about 300 GeV, in the most straightforward way, i.e. via the introduction of a chiral singlet $S$ with a superpotential interaction with the Higgs doublets, $\ensuremath{\lambda}S{H}_{1}{H}_{2}$. The coupling $\ensuremath{\lambda}$ dominates over all the other couplings and, to maintain the successful perturbative analysis of the electroweak precision tests, is only restricted to remain perturbative up to about 10 TeV. The general features of this ``$\ensuremath{\lambda}\mathrm{SUSY}$'' framework, which deviates significantly from the minimal supersymmetric standard model or the standard next to minimal supersymmetric standard model, are analyzed in different areas: electroweak precision tests, dark matter, naturalness bounds on superparticle masses, and LHC signals. There is a rich Higgs/Higgsino sector in the (200--700) GeV mass region, which may include LSP Higgsino dark matter. All other superpartners, apart from the top squarks, may naturally be heavier than 1--2 TeV.

Mixed Higgsino Dark Matter from a reduced SU(3) gaugino mass: consequences for dark matter and collider searches

In gravity-mediated SUSY breaking models with non-universal gaugino masses, lowering the SU(3) gaugino mass |M_3| leads to a reduction in the squark and gluino masses. Lower third generation squark masses, in turn, diminish the effect of a large top quark Yukawa coupling in the running of the higgs mass parameter m_{H_u}^2, leading to a reduction in the magnitude of the superpotential mu parameter (relative to M_1 and M_2). A low | mu | parameter gives rise to mixed higgsino dark matter (MHDM), which can efficiently annihilate in the early universe to give a dark matter relic density in accord with WMAP measurements. We explore the phenomenology of the low |M_3| scenario, and find for the case of MHDM increased rates for direct and indirect detection of neutralino dark matter relative to the mSUGRA model. The sparticle mass spectrum is characterized by relatively light gluinos, frequently with m(gl)<<m(sq). If scalar masses are large, then gluinos can be very light, with gl->Z_i+g loop decays dominating the gluino branching fraction. Top squarks can be much lighter than sbottom and first/second generation squarks. The presence of low mass higgsino-like charginos and neutralinos is expected at the CERN LHC. The small m(Z2)-m(Z1) mass gap should give rise to a visible opposite-sign/same flavor dilepton mass edge. At a TeV scale linear e^+e^- collider, the region of MHDM will mean that the entire spectrum of charginos and neutralinos are amongst the lightest sparticles, and are most likely to be produced at observable rates, allowing for a complete reconstruction of the gaugino-higgsino sector.

Higgsino dark matter in partly supersymmetric models

Models where supersymmetry (SUSY) is manifest only in a sector of the low-energy spectrum have been recently proposed as an alternative to the MSSM. In these models the electroweak scale is explained by a fine-tuning between different Higgs mass contributions (split-SUSY models), or by the localization of the Higgs sector in a point of an extra dimension where all the mass parameters are suppressed by the metric (partly-SUSY models). Therefore, the presence of a good dark matter candidate becomes the main motivation for (partial) low-energy SUSY. We study this issue in minimal frameworks where the higgsinos are the only light supersymmetric particles. Whereas in split-SUSY models the higgsino should have a mass around 1 TeV, we show that in partly-SUSY models the lightest higgsino could also be found below MW.

Direct, indirect and collider detection of neutralino dark matter in SUSY models with non-universal Higgs masses

In supersymmetric models with gravity-mediated SUSY breaking, universality of soft SUSY breaking sfermion masses m_0 is motivated by the need to suppress unwanted flavor changing processes. The same motivation, however, does not apply to soft breaking Higgs masses, which may in general have independent masses from matter scalars at the GUT scale. We explore phenomenological implications of both the one-parameter and two-parameter non-universal Higgs mass models (NUHM1 and NUHM2), and examine the parameter ranges compatible with Omega_CDM h^2, BF(b --> s,gamma) and (g-2)_mu constraints. In contrast to the mSUGRA model, in both NUHM1 and NUHM2 models, the dark matter A-annihilation funnel can be reached at low values of tan(beta), while the higgsino dark matter annihilation regions can be reached for low values of m_0. We show that there may be observable rates for indirect and direct detection of neutralino cold dark matter in phenomenologically aceptable ranges of parameter space. We also examine implications of the NUHM models for the Fermilab Tevatron, the CERN LHC and a Sqrt(s)=0.5-1 TeV e+e- linear collider. Novel possibilities include: very light s-top_R, s-charm_R squark and slepton_L masses as well as light charginos and neutralinos and H, A and H^+/- Higgs bosons.

Dark matter in the finely tuned minimal supersymmetric standard model

We explore dark matter in the finely-tuned minimal supersymmetric standard model (MSSM) recently proposed by Arkani-Hamed and Dimopoulos. Relative to the MSSM, there are fewer particles at freeze-out, so the calculation of the relic abundance simplifies. Similarly, the predictions for direct detection of the dark matter sharpen. There is a large region of mixed bino---higgsino dark matter where the lightest supersymmetric particle will be accessible at both the LHC and future direct detection experiments, allowing for a conclusive identification of the dark matter particle. Typical dark matter-nucleon cross sections are ${10}^{\ensuremath{-}45}\ensuremath{-}{10}^{\ensuremath{-}44}\text{ }\text{ }{\mathrm{c}\mathrm{m}}^{2}$. This model also possesses a novel region where the dark matter annihilates via an $s$-channel Higgs boson resonance.

Higgsino dark matter in a supergravity model with nonuniversal gaugino masses

We study a specific SUGRA model with nonuniversal gaugino masses as an alternative to the minimal SUGRA model in the context of supersymmetric dark matter. The lightest supersymmetric particle in this model comes out to be a Higgsino dominated instead of a bino dominated lightest neutralino. The thermal relic density of this Higgsino dark matter is somewhat lower than the cosmologically favoured range, which means it may be only a subdominant component of the cold dark matter. Nonetheless, it predicts favourable rates of indirect detection, which can be seen in square-km size neutrino telescopes.