Search for MeV dark photons in a light-shining-through-walls experiment at CERN

TL;DR

This paper proposes a high-energy electron beam experiment at CERN to search for dark photons via a light-shining-through-walls method, aiming to explore new parameter space and detect potential dark matter interactions.

Contribution

It introduces a novel experimental setup using CERN SPS electron beams to search for dark photons in unexplored mass and mixing ranges, including invisible decay channels.

Findings

Design of a light-shining-through-walls experiment at CERN.

Potential to probe dark photon mixing strength 10^{-5} to 10^{-3}.

Capability to detect dark photons decaying invisibly to dark-sector particles.

Abstract

In addition to gravity, there might be another very weak interaction between the ordinary and dark matter transmitted by U'(1) gauge bosons A' (dark photons) mixing with our photons. If such A's exist, they could be searched for in a light-shining-through-a-wall experiment with a high energy electron beam. The electron energy absorption in a calorimeter (CAL1) is accompanied by the emission of bremsstrahlung A's in the reaction eZ -> eZA' of electrons scattering on nuclei due to the \gamma - A' mixing. A part of the primary beam energy is deposited in the CAL1, while the rest of the energy is transmitted by the A' through the "CAL1 wall" and deposited in another downstream calorimeter CAL2 by the e+e- pair from the A'->e+e- decay in flight. Thus, the A's could be observed by looking for an excess of events with the two-shower signature generated by a single high energy electron in the CAL1 and CAL2. A proposal to perform such an experiment to probe the still unexplored area of the mixing strength 10^{-5} < \epsilon < 10^{-3} and masses M_{A'} < 100 MeV by using 10-300 GeV electron beams from the CERN SPS is presented. The experiment can provide complementary coverage of the parameter space, which is intended to be probed by other searches. It has also a capability for a sensitive search for A's decaying invisibly to dark-sector particles, such as dark matter, which could cover a significant part of the still allowed parameter space.