Constraints on the dark photon from parity-violation and the W-mass

Abstract

We present an analysis of the experimental data for parity-violating electron scattering (PVES) and atomic parity-violation, including the effects of a dark photon. We derive the favored region of dark photon parameter space, which provides a good description of the experimental data from the Qweak Collaboration and the Jefferson Lab PVDIS Collaboration and simultaneously relieves the tension between the neutron skin thickness determined in the PREX-II experiment and nuclear-model predictions. In addition, we extract the parameter region required to explain the latest W-boson mass anomaly. Our results indicate that a heavy dark photon with mass above the Z boson mass is favored, while other sources of new physics beyond the Standard Model in addition to the dark photon would also be expected.

A triplet gauge boson with hypercharge one

“…The two models are based on an SO( 5)×SU (2)× U (1) extended electroweak group, and therefore they predict the existence of a W ′ and a Z ′ , with a mass hierarchy m W 1 < m Z ′ < m W ′ . Incidentally, these two vector fields are known to affect the W mass (see [3,8,10,[31][32][33][34]): W ′ pulls it down and Z ′ has the opposite effect. Since the Z ′ is lighter, it could in principle explain the CDF data.…”

Global QCD analysis and dark photons

“…Large regions of parameter space with mixing parameter > 10 −3 in both light and heavy mass regions have been ruled out [9], with a few gaps, which are significant in the light of our results, associated with the production of resonances, such as the J/ψ and its excited states. Further competitive constraints have recently been placed on the dark photon from "decay-agnostic" (independent of decay modes or production mechanism) processes, such as the muon g − 2 anomaly [10,11], the electroweak precision observables (EWPO) [12][13][14], e ± p deep-inelastic scattering (DIS) [15][16][17], parity-violating electron scattering [18,19], rare kaon and B-meson decays [20,21], and high-luminosity LHC projections [22]. The dark photon contributes to DIS processes coherently along with photon and Z boson exchange, as illustrated in figure 1.…”