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

TL;DR

This paper proposes a new method for detecting Light Dark Matter using electron beam-dump experiments, leveraging positron annihilation to improve sensitivity beyond existing limits.

Contribution

It introduces a novel production mechanism via positron annihilation, enhancing detection sensitivity in beam-dump experiments for Light Dark Matter.

Findings

Resonant annihilation yields higher sensitivity than $A'$-strahlung.

Method reduces current experimental limits by an order of magnitude.

Applicable to both standard and active 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 ($e^+ + e^- \to \gamma + A^\prime$) 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.