Evidence for and implications of a dark photon

TL;DR

This paper presents the first global QCD analysis including a dark photon, showing a significant statistical preference for its existence over the Standard Model and exploring various experimental implications.

Contribution

It introduces the first comprehensive analysis of dark photon effects in high-energy scattering data, indicating potential evidence for dark photons beyond previous searches.

Findings

Dark photon fit preferred over Standard Model by 6.5 sigma

Significant reduction in chi-squared with dark photon inclusion

Implications for electron scattering, kaon decay, and electroweak observables

Abstract

We performed the first global QCD analysis of electron-nucleon deep-inelastic scattering and related high-energy data by including the contribution from a dark photon. Our results revealed a significant reduction in $\chi^2$ relative to the baseline result without new physics. From a hypothesis test, our best dark photon fit is preferred over the Standard Model by as much as $6.5\ \sigma$, providing the first hint for the existence of a dark photon, although indirectly. Additionally, we explored the implications of a dark photon in party-violating electron scattering, rare kaon decay, and the electroweak precision observables. The dark photon as a portal connecting to dark matter particles was also discussed.