Muon Anomaly and Dark Parity Violation

TL;DR

This paper explores how a proposed light vector boson, Z_d, could explain the muon g-2 anomaly and induce observable dark parity violation effects in atomic and electron scattering experiments, providing a new avenue for detection.

Contribution

It introduces the concept of dark parity violation via Z_d-Z mixing and assesses experimental bounds and future sensitivities for detecting this phenomenon.

Findings

Existing atomic parity violation results constrain the mixing parameter.

Future experiments could reach sensitivities that probe the predicted dark parity violation.

The proposed model links muon g-2 discrepancy with potential observable effects in low-energy experiments.

Abstract

The muon anomalous magnetic moment exhibits a 3.6 \sigma discrepancy between experiment and theory. One explanation requires the existence of a light vector boson, Z_d (the dark Z), with mass 10 - 500 MeV that couples weakly to the electromagnetic current through kinetic mixing. Support for such a solution also comes from astrophysics conjectures regarding the utility of a U(1)_d gauge symmetry in the dark matter sector. In that scenario, we show that mass mixing between the Z_d and ordinary Z boson introduces a new source of "dark" parity violation which is potentially observable in atomic and polarized electron scattering experiments. Restrictive bounds on the mixing (m_{Z_d} / m_Z) \delta are found from existing atomic parity violation results, \delta^2 < 2 x 10^{-5}. Combined with future planned and proposed polarized electron scattering experiments, a sensitivity of \delta^2 ~ 10^{-6} is expected to be reached, thereby complementing direct searches for the Z_d boson.