Dark photon effect on the rare kaon decay KL⃗π0νν¯

Abstract

We present an analysis of the effect of a dark photon on the rare kaon decay $K_L \rightarrow \pi^0 \nu {\bar \nu}$. All relevant couplings of the dark photon to the Standard Model particles are derived explicitly in terms of the dark photon mass and the mixing parameter. We find that the dark photon yields no more than a few percent correction to the Standard Model branching ratio ${\rm Br}(K_L \rightarrow \pi^0 \nu {\bar \nu})$ in the region of interest.

Constraints on the dark sector from electroweak precision observables

“…All the physical couplings in equation (8) depend on three parameters: mZ , m A D , and ò. In other analyses [9,19,21,22,25] where the physical m Z is fixed at its experimental value, only two parameters are independent, with m A D and ò as the usual choice.…”

“…Theoretical investigations have also placed decay-agnostic constraints on the dark photon parameters by exploring the consequences for many physical processes and then using relevant experiments to constrain parameters. The physics processes considered include measurements of the g−2 of the muon [14,15], electroweak precision observables (EWPO) [16,17], e − p DIS [18][19][20], parity violating electron scattering [21,22], partial wave unitarity [23], rare kaon and B-meson decays [24,25], and high-luminosity LHC projections [26].…”

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.…”