Abstract
Recent results from direct and indirect searches for dark matter (DM) have motivated the study of particle physics models that can provide weakly interacting massive particles (WIMPs) in the mass range 1–50 GeV. Viable candidates for light WIMP DM must fulfil stringent constraints. On the one hand, the observation at the LHC of a Higgs boson with Standard Model properties set an upper bound on the coupling of light DM particles to the Higgs, thereby making it difficult to reproduce the correct relic abundance. On the other hand, the recent results from direct searches in the CDMSlite, SuperCDMS and LUX experiments have set upper constraints on the DM scattering cross section. In this paper, we investigate the viability of light right-handed sneutrino DM in the Next-to-Minimal Supersymmetric Model (NMSSM) in the light of these constraints. To this aim, we have carried out a scan in the NMSSM parameter space, imposing experimental bounds on the Higgs sector and low-energy observables, such as the muon anomalous magnetic moment and branching ratios of rare decays. We demonstrate that the enlarged Higgs sector of the NMSSM, together with the flexibility provided by the RH sneutrino parameters, make it possible to obtain viable RH sneutrino DM with a mass as light as 2 GeV. We have also considered the upper bounds on the annihilation cross section from Fermi LAT data on dwarf spheroidal galaxies, and extracted specific examples with mass in the range 8–50 GeV that could account for the apparent low-energy excess in the gamma-ray emission at the Galactic Centre. Then, we have computed the theoretical predictions for the elastic scattering cross-section of RH sneutrinos. Finally, after imposing the recent bounds from SuperCDMS and LUX, we have found a wide area of the parameter space that could be probed by future low-threshold direct detection experiments.
Highlights
It has been argued that Fermi LAT observations of the gamma ray flux from the Galactic Centre (GC) show a small excess at low energies that could be explained in terms of dark matter (DM) particles [20,21,22,23,24,25,26,27] with a mass in the range 10 − 60 GeV, depending on the specific annihilation channel, and an annihilation cross-section which is remarkably close to that expected for a thermal weakly interacting massive particles (WIMPs)
Due to the correlation between diagrams that contribute to the DM annihilation and direct detection, it has been shown in several examples that if the Standard Model (SM) Higgs is the only mediator between the DM and the SM particles the current constraint on BR(h0SM → χχ) rules out very light WIMPs
We demonstrate that the enlarged Higgs sector of the Next-to-minimal Supersymmetric Standard Model (NMSSM), together with the flexibility provided by the RH sneutrino parameters, make it possible to obtain viable RH sneutrino DM with a mass as low as 2 GeV
Summary
The model, described in refs. [60, 61], is an extended version of the NMSSM, in which a right-handed neutrino superfield N , singlet under the SM gauge group, is added in order to account for RH neutrino and sneutrino states. In order to reproduce the light left-handed (LH) neutrino masses, the see-saw mechanism relation implies that yN has to be similar to the electron Yukawa, yN ∼ 10−6, typical value of a low-scale see-saw mechanism This leads to a very small left-right mixing in both the neutrino and sneutrino sectors and the mass eigenstates can be identified with the LH and RH components. [60, 61] that the RH sneutrino can be a viable candidate for WIMP DM, reproducing the correct relic abundance for a wide range of masses, including cases in which the RH sneutrino is very light [65] The flexibility of this construction stems from the fact that the new free parameters (λN , mN , AλN ) can be chosen to fix the RH sneutrino mass and its coupling to the singlet Higgs boson without affecting the rest of the NMSSM spectrum. (vii) γγ, Zγ, via a loop of H± and s-channel Higgs exchange with a loop of quarks, W ±, H±, charginos and sfermions
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