Constraints on dark photons from $\pi^0$ decays

TL;DR

This paper constrains the properties of hypothetical dark photons by analyzing b0 meson decays and using experimental data to limit their mixing with ordinary photons in a specific mass range.

Contribution

It provides new bounds on dark photon parameters based on b0 decay data and experimental searches for e+e- pairs, refining the parameter space for dark photon models.

Findings

Excluded b0-photon mixing b5 > 10^{-3} for 25 < M_{A'} < 120 MeV

Derived constraints from SINDRUM experiment data

Set limits on dark photon mass and mixing parameters

Abstract

Several models of dark matter suggest the existence of hidden sectors consisting of SU(3)_C x SU(2)_L x U(1)_Y singlet fields. The interaction between the ordinary and hidden sectors could be transmitted by new Abelian U'(1) gauge bosons A' (dark or hidden photons) mixing with ordinary photons. If such A's have masses below the \pi^0 meson mass, they would be produced through \gamma - A' mixing in the \pi^0 ->2\gamma - decays and be observed via their decays A' -> e+e- in a detector. Using bounds from the SINDRUM experiment at the Paul Scherrer Institute that searched for an excess of e+e- pairs in \pi^- p interactions at rest, the area excluding the \gamma - A' mixing \epsilon > 10^{-3} for the A' mass region 25 < M_{A'} < 120 MeV is derived.