Nucleosynthesis constraints on the faint vector portal

TL;DR

This paper investigates how early Universe nucleosynthesis constrains the properties of hypothetical light vector bosons that interact with the Standard Model via kinetic mixing, providing bounds on their mixing strength and mass.

Contribution

It offers the first detailed calculation of relic abundance and nucleosynthesis constraints on GeV-scale vector portal gauge bosons with extremely small mixing parameters.

Findings

Constraints on mixing parameter $\kappa$ down to $10^{-14}$ for GeV-scale vectors.

Probes of vector masses in the GeV range through nucleosynthesis data.

No terrestrial experiments currently test the parameter space explored.

Abstract

New Abelian U(1)' gauge bosons $V_{\mu}$ can couple to the Standard Model through mixing of the associated field strength tensor $V_{\mu\nu}$ with the one from hypercharge, $F_{\mu\nu}^Y$. Here we consider early Universe sensitivity to this vector portal and show that the effective mixing parameter with the photon, $\kappa$, is being probed for vector masses in the GeV ballpark down to values $10^{-10} \lesssim \kappa \lesssim 10^{-14}$ where no terrestrial probes exist. The ensuing constraints are based on a detailed calculation of the vector relic abundance and an in-depth analysis of relevant nucleosynthesis processes.