Fits to the Fermi-LAT GeV excess with right-handed sneutrino dark matter: Implications for direct and indirect dark matter searches and the LHC

We show that the right-handed (RH) sneutrino in the next-to-minimal supersymmetric standard model can account for the observed excess in the Fermi-LAT spectrum of gamma rays from the Galactic center, while fulfilling all the current experimental constraints from the LHC as well as from direct and indirect dark matter searches. We have explored the parameter space of this scenario, computed the gamma-ray spectrum for each phenomenologically viable solution and then performed a ${\chi }^2$ fit to the excess. Unlike previous studies based on model-independent interpretations, we have taken into account the full annihilation spectrum, without assuming pure annihilation channels. Furthermore, we have incorporated limits from direct detection experiments, LHC bounds and also the constraints from Fermi-LAT on dwarf spheroidal galaxies and gamma-ray spectral lines. In addition, we have estimated the effect of the most recent Fermi-LAT reprocessed data (pass 8). In general, we obtain good fits to the Galactic center excess (GCE) when the RH sneutrino annihilates mainly into pairs of light singletlike scalar or pseudoscalar Higgs bosons that subsequently decay in flight, producing four-body final states and spectral features that improve the goodness of the fit at large energies. The best fit (${\chi }^2=20.8$) corresponds to a RH sneutrino with a mass of 64 GeV which annihilates preferentially into a pair of light singletlike pseudoscalar Higgs bosons (with masses of order 60 GeV). Besides, we have analyzed other channels that also provide good fits to the excess. Finally, we discuss the implications for direct and indirect detection searches paying special attention to the possible appearance of gamma-ray spectral features in near future Fermi-LAT analyses, as well as deviations from the Standard Model–like Higgs properties at the LHC. Remarkably, many of the scenarios that fit the GCE can also be probed by these other complementary techniques.

Figure 1

RH sneutrino annihilation diagrams that produce lines and box-shaped features in the gamma-ray spectrum.

Figure 2

Velocity-averaged annihilation cross section of RH sneutrinos in the Galactic halo as a function of the RH sneutrino mass. All the points provide a fit to the GCE at 95% C.L. We have also imposed all the experimental bounds, including dSph constraints and Fermi-LAT searches for spectral lines. The color code indicates different dominant final states of the RH sneutrino annihilation. The best fit points for each annihilation channel are represented by a star. Points allowed by our estimation of the pass 8 dSph bounds are encircled in black.

Figure 3

Differential gamma-ray spectrum for the points in Table 1 for pure (left panel) and predominant (right panel) annihilation channels. The color convention is as in Fig. 2. The experimental data and errors are extracted from Ref. [10], as well as the best fit for a pure $b\overline{b}$ channel, represented by a black dashed line.

Figure 4

Theoretical predictions for ${\sigma }_{{\tilde{N}}_{1}p}^{\mathrm{SI}}$ as a function of $m_{{\tilde{N}}_1}$ for points which fit the GCE at 95% C.L. and fulfil all the experimental bounds. The color convention is as in Fig. 2. Solid lines represent the current experimental upper bounds from direct detection experiments, whereas dotted lines are the projected sensitivities of next-generation detectors. The dashed line corresponds to an approximate band where neutrino coherent scattering with nuclei will begin to limit the sensitivity of direct detection experiments. Closed contours represent the areas compatible with the observed excesses in DAMA/LIBRA (orange), CRESST (red), CDMS II (blue), and CoGeNT (green).

Figure 5

$R_{\gamma \gamma }$ ratio as a function of the photon energy $E_{\gamma }$ for which the ratio is maximized. All the points fulfil all the experimental bounds. The color convention is as in Fig. 2. The dashed line denotes our estimation of the improved sensitivity to spectral feature searches with Fermi-LAT pass 8 data.

Figure 6

Branching ratio of the SM-Higgs $H_2^0$ into non-SM particles as a function of its invisible branching ratio. All the points fulfil all the experimental bounds. The color convention is as in Fig. 2. The regions above the dashed line and to the right of the dot-dashed line will be probed by future searches at the LHC.

Figure 7

Left: $m_{A_1^0}$ as a function of $m_{H_1^0}$ for the points fulfilling all the experimental constraints and fitting the GCE at 95% C.L. with the color convention as in Fig. 2. Right: Mass ranges for the Higgs sector and the different supersymmetric particles corresponding to the viable points in the parameter space.

Figure 8

Left: $\kappa$ versus $\lambda$ for the points that fulfil all the experimental constraints and fit the GCE at 95% C.L. with the color convention as in Fig. 2. Right: The same but for the $\tan \beta$ and $\mu$ parameters.

Figure 9

$m_{H_1^0}$ versus $m_{{\tilde{N}}_1}$ for the points fulfilling all the experimental constraints and fitting the GCE at 95% C.L. with the color convention as in Fig. 2. The solid line corresponds to $m_{H_1^0}=m_{{\tilde{N}}_1}$ while the dashed line denotes the resonant annihilation condition $m_{H_1^0}=m_{{\tilde{N}}_1}/2$.