Interpretations of galactic center gamma-ray excess confronting the PandaX-II constraints on dark matter-neutron spin-dependent scatterings in the NMSSM

Abstract The Weakly Interacting Massive Particle (WIMP) has been one of the most attractive candidates for Dark Matter (DM), and the lightest neutralino ($$\widetilde{\chi }^0_1$$ χ~10 ) in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) is an interesting realization of the WIMP framework. The Galactic Center Excess (GCE) indicated from the analysis of the photon data of the Fermi Large Area Telescope (Fermi-LAT) in the gamma-ray wavelength $$\lesssim 1 \,\mathrm{fm}$$ ≲1fm , can be explained by WIMP DM annihilations in the sky, as shown in many existing works. In this work we consider an interesting scenario in the $$Z_3$$ Z3 -NMSSM where the singlet S and Singlino $$\widetilde{S}^0$$ S~0 components play important roles in the Higgs and DM sector. Guided by our analytical arguments, we perform a sophisticated scan over the NMSSM parameter space by considering various observables such as the Standard Model (SM) Higgs data measured by the ATLAS and CMS experiments at the Large Hadron Collider (LHC), and the B-physics observables $$BR(B_s\rightarrow X_s\gamma )$$ BR(Bs→Xsγ) and $$BR(B_s\rightarrow \mu ^+\mu ^-)$$ BR(Bs→μ+μ-) . We first collect samples which can explain the GCE well while passing all constraints we consider except for the DM direct detection (DD) bounds from XENON1T and PandaX-II experiments. We analyze the features of these samples suitable for the GCE interpretation and find that $$\widetilde{\chi }^0_1$$ χ~10 DM are mostly Singlino-like and annihilation products are mostly the bottom quark pairs $$\bar{b}b$$ b¯b through a light singlet-like CP-odd Higgs $$A_1$$ A1 . Moreover, a good fit to the GCE spectrum generically requires sizable DM annihilation rates $$\langle \sigma _{b\bar{b}} v \rangle _{0}$$ ⟨σbb¯v⟩0 in today’s Universe. However, the correlation between the coupling $$C_{A_1 b\bar{b}}$$ CA1bb¯ in $$\langle \sigma _{b\bar{b}} v \rangle _{0}$$ ⟨σbb¯v⟩0 and the coupling $$C_{Z \widetilde{\chi }^0_1 \widetilde{\chi }^0_1}$$ CZχ~10χ~10 in DM-neutron Spin Dependent (SD) scattering rate $$\sigma ^{SD}_{\widetilde{\chi }^0_1-N}$$ σχ~10-NSD makes all samples we obtain for GCE explanation get excluded by the PandaX-II results. Although the DM resonant annihilation scenarios may be beyond the reach of our analytical approximations and scan strategy, the aforementioned correlation can be a reasonable motivation for future experiments such as PandaX-nT to further test the NMSSM interpretation of GCE