A novel way to search for light dark matter in lepton beam-dump experiments

Abstract

A novel mechanism to produce and detect Light Dark Matter in experiments making use of GeV electrons (and positrons) impinging on a thick target (beam-dump) is proposed. The positron-rich environment produced by the electromagnetic shower allows to produce an $A^{\prime }$ via non-resonant ($e^{+}+e^{-}\to {\hat{I}}^3+A^{\prime }$) and resonant ($e^{+}+e^{-}\to A^{\prime }$) annihilation on atomic electrons. The latter mechanism, for some selected kinematics, results in a larger sensitivity with respect to limits derived by the commonly used $A^{\prime }-strahlung$. This idea, applied to Beam Dump Experiments and {\it active} Beam Dump Experiments pushes down the current limits by an order of magnitude.

5 pages, 3 figures