Abstract
We study spectral features in the gamma-ray emission from dark matter (DM) annihilation in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), with either neutralino or right-handed (RH) sneutrino DM . We perform a series of scans over the NMSSM parameter space, compute the DM annihilation cross section into two photons and the contribution of box-shaped features, and compare them with the limits derived from the Fermi-LAT search for gamma-ray lines using the latest Pass 8 data. We implement the LHC bounds on the Higgs sector and on the masses of supersymmetric particles as well as the constraints on low-energy observables. We also consider the recent upper limits from the Fermi-LAT satellite on the continuum gamma-ray emission from dwarf spheroidal galaxies (dSphs). We show that in the case of the RH sneutrino the constraint on gamma-ray spectral features can be more stringent than the dSph bounds. This is due to the Breit-Wigner enhancement near the ubiquitous resonances with a CP even Higgs and the contribution of scalar and pseudoscalar Higgs final states to box-shaped features. By contrast, for neutralino DM, the di-photon final state is only enhanced in the resonance with a Z boson and box-shaped features are even more suppressed. Therefore, the observation of spectral features could constitute a discriminating factor between both models. In addition, we compare our results with direct DM searches, including the SuperCDMS and LUX limits on the elastic DM-nucleus scattering cross section and show that some of these scenarios would be accessible to next generation experiments. Thus, our findings strengthen the idea of complementarity among distinct DM search strategies.
Highlights
We perform a series of scans over the Next-to-Minimal Supersymmetric Standard Model (NMSSM) parameter space, compute the dark matter (DM) annihilation cross section into two photons and the contribution of box-shaped features, and compare them with the limits derived from the Fermi-LAT search for gamma-ray lines using the latest Pass 8 data
The Fermi-LAT low-energy excess in the Galactic Centre Emission (GCE) [18] stands out, as it could be explained in terms of WIMP DM, with a mass in the 6–200 GeV range and an annihilation cross section compatible with that of thermal relics
Each panel corresponds to a different assumption of the DM density profile, the top left panel corresponds to a NFW, top right to an Einasto, bottom left panel to a NFW with adiabatic contraction (NFWc), and bottom right to an isothermal density profile
Summary
The modifications in the neutralino sector due to the inclusion of a singlino component and the presence of new annihilation channels have profound consequences for DM searches, which have been extensively discussed in the literature [56,57,58,59,60]. [31], the authors showed that for neutralinos lighter than 100 GeV in the NMSSM, the cross section for the γγ final state is typically of the order of 10−31 cm s−1 for either bino-like, singlino-like or mixed neutralinos This value can increase several orders of magnitude when neutralinos have a resonant annihilation mediated by a very light CP-odd Higgs with a fermion loop, reaching σv γγ ≈ 10−27 cm s−1 [31, 73,74,75]. We take into account the most recent bounds from direct and indirect DM searches To this aim, we first compute the monochromatic gamma-ray spectrum for a series of scans over the parameter space and determine the observability of this signal. The contribution from VIB can exceed that from final state radiation [44, 77] and in some cases be more observable than gamma-ray lines [78] We will later argue that these conditions are not satisfied in our scan
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