Explaining the DAMPE data with scalar dark matter and gauged U(1)_{L_e-L_mu } interaction

Abstract

Inspired by the peak structure observed by recent DAMPE experiment in e^+e^- cosmic-ray spectrum, we consider a scalar dark matter (DM) model with gauged U(1)_{L_e-L_mu } symmetry, which is the most economical anomaly-free theory to potentially explain the peak by DM annihilation in nearby subhalo. We utilize the process chi chi rightarrow Z^prime Z^prime rightarrow l bar{l} l^prime bar{l}^prime , where chi , Z^prime , l^{(prime )} denote the scalar DM, the new gauge boson and l^{(prime )} =e, mu , respectively, to generate the e^+e^- spectrum. By fitting the predicted spectrum to the experimental data, we obtain the favored DM mass range m_chi simeq 3060^{+80}_{-100} , mathrm{GeV} and Delta m equiv m_chi - m_{Z^prime } lesssim 14 , mathrm{GeV} at 68% Confidence Level (C.L.). Furthermore, we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from DM relic abundance, DM direct detection and the collider bounds. We conclude that the model we consider can account for the peak, although there exists a tension with the constraints from the LEP-II bound on m_{Z^prime } arising from the cross section measurement of e^+e^- rightarrow Z^{prime *} rightarrow e^+ e^-.