Searching for an invisible A' vector boson with DarkLight

TL;DR

The paper explores DarkLight's potential to detect an invisible A' vector boson in low-energy experiments, proposing new analysis techniques and comparing its sensitivity to other experiments.

Contribution

It demonstrates DarkLight's sensitivity to invisible A' bosons, introduces novel analysis methods, and compares its reach with other experimental proposals.

Findings

DarkLight can detect invisible A' bosons with specific sensitivity levels.

New analysis techniques improve invariant mass resolution and pileup mitigation.

DarkLight's reach is competitive with other low-energy experiments.

Abstract

High-luminosity experiments are able to search for new physics at low energies, which could have evaded detection thus far due to very weak couplings to the Standard Model. The DarkLight experiment at Jefferson Lab is designed to search for a new U(1) vector boson A' in the mass range 10-100 MeV through its decay A' -> e+ e-. In this paper, we demonstrate that DarkLight is also sensitive to an A' decaying to invisible final states. We analyze the DarkLight reach for invisible A' bosons assuming a nominal two month running time, including the possibility of augmenting the DarkLight design to include photon detection. We also propose two new analysis techniques that might prove useful for other high-luminosity searches: a cut on missing energy to improve the invariant mass resolution, and a cut on the sign of the missing invariant mass-squared to mitigate pileup. We compare the DarkLight reach to existing experimental proposals, including a complementary search using the VEPP-3 positron beam.