Missing energy signatures of inelastic magnetic dipole DM at NA64e

Abstract

Some extensions of the Standard Model consider inelastic dark matter (iDM) as an attractive candidate for sub-GeV DM of thermal origin that could be detected at modern accelerators. In the present paper, we calculate the production rate of iDM pairs ${\chi }_1{\bar{\chi }}_0$ interacting with the ordinary photon via dipole magnetic moment in the reaction of high-energy electron scattering on nuclei, $e^{-}N\to e^{-}N{\chi }_1{\bar{\chi }}_0$, in the NA64e experiment at the CERN SPS. We derive the projected sensitivity of NA64e to such particles assuming of $\simeq 10^{13}$ 100 GeV electrons on target. We also show, that incorporating heavy vector meson decays, ${\gamma }^{\ast }N\to NV(\to {\chi }_1{\bar{\chi }}_0)$, alongside bremsstrahlung-like emission of inelastic dark matter pairs, $e^{-}N\to e^{-}N{\gamma }^{\ast }(\to {\chi }_1{\bar{\chi }}_0)$, will allow NA64e to probe previously unexplored regions of the iDM parameter space, in particular for modest mass splittings, $\Delta \simeq 5\times 10^{-2}$, and relatively light masses, $m_{{\chi }_0}\lesssim 100\text{mbox}MeV$.

Comments: 8 pages, 5 figures