Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations

The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern $\gamma$-ray sky at energies above 10 TeV with unprecedented sensitivity. $\gamma$-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy $\gamma$ rays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from $1/2$-KM2A and 230 days of data from $3/4$-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after $\gamma /\text{hadron}$ separation. We find no excess of dark matter signals, and thus place some of the strongest $\gamma$-ray constraints on the lifetime of heavy dark matter particles with mass between ${10}^5$ and ${10}^9\mathrm{GeV}$. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.

Figure 1

95% one-sided lower limits on DM lifetime obtained with the profile likelihood analysis (thick black lines), for DM decaying into $b$ quarks (left) or $\tau$ leptons (right). The black dashed line shows the limit obtained if we only consider prompt DM contribution. The green and yellow bands correspond to the expected 68% and 95% limit ranges from Monte Carlo simulations with the background-only hypothesis. Previous limits [59, 69, 76] and those from HAWC [11] are shown with gray and blue lines. The hatched regions show the $1\sigma$ DM parameter space favored by IceCube high-energy neutrino flux [67].