Implications of a Running Dark Photon Coupling

TL;DR

This paper explores how the running of the dark photon's coupling constant and kinetic mixing parameter with momentum transfer could be detectable in dark matter experiments, impacting the understanding of dark sector interactions.

Contribution

It introduces the concept that the running of the dark photon coupling and kinetic mixing can have observable effects in experiments, providing new insights into dark sector physics.

Findings

Running of $eta_{d}$ can be significant at high momentum transfer

Kinetic mixing parameter $ ext{varepsilon}^2$ depends on $ ext{alpha}_d(q)$

Theoretical bounds suggest $ ext{alpha}_d(m_{Z_d}) extless 0.5$

Abstract

For an "invisible" dark photon $Z_d$ that dominantly decays into dark states, the running of its fine structure constant $\alpha_d$ with momentum transfer $q > m_{Z_d}$ could be significant. A similar running in the kinetic mixing parameter $\varepsilon^2$ can be induced through its dependence on $\alpha_d(q)$. The running of couplings could potentially be detected in "dark matter beam" experiments, for which theoretical considerations imply $\alpha_d (m_{Z_d}) \lesssim 0.5$.