Dark Matter emission at Belle II and NA62 in Minimal Flavor Violation framework

TL;DR

This work tests dark matter scenarios within Minimal Flavor Violation by promoting DM to MFV-protected multiplets that couple to quarks through flavor-aligned operators, enabling dark particle emission in $d_i\to d_j + \slashed{E}$ decays. By combining NA62, Belle II, KOTO, Belle, and BaBar data, the authors perform a likelihood analysis for scalar and fermion DM in representations that yield down-quark flavor violation, finding that a single nearly-degenerate DM multiplet can explain either the Kaon or the B-mmeson missing-energy excesses at about the $3\sigma$ level, but not both simultaneously. They show that achieving a unified explanation requires either introducing an additional DM multiplet with flavor-dependent masses or introducing larger MFV-approved mass splittings, moving beyond minimality. The results emphasize a fruitful interplay between MFV-based model building and precision flavor experiments, highlighting flavored DM as a testable framework capable of addressing missing-energy signatures and potentially contributing to the dark matter puzzle. Overall, the paper maps the viable MFV DM parameter space in light of current anomalies and outlines concrete non-minimal extensions that could reconcile competing flavor hints.

Abstract

Minimal Flavor Violation (MFV) provides a compelling framework for exploring physics beyond the Standard Model, in which new QCD-singlet fields transforming under the global $\mathrm{SU}(3)^3$ quark flavor symmetry can naturally be stable and act as dark matter (DM) candidates. We show that the DM-MFV framework naturally accommodates the excess in either $K^+ \to π^+ ν\barν$ or $B^+ \to K^+ ν\barν$, while a unified explanation of both channels simultaneously cannot be achieved within a minimal setup containing only a single dark matter multiplet with nearly degenerate masses. Overall, our findings underscore the intricate interplay between MFV-based model building, flavored dark matter scenarios, and precision flavor experiments, highlighting flavored dark matter as a framework that is both theoretically robust and experimentally testable.

Figures (2)

• Figure 1: Results for the case of scalar DM $S\sim(3,1,1)$. Left: test statistic as a function of the scalar mass, $m_{S}$. Right: best-fit value of new physics parameter, $\Lambda$, as a function of the scalar mass.
• Figure 2: Results for the case of fermion DM $\psi\sim(3,1,1)$. Left: test statistic as a function of the fermion mass, $m_{\psi}$. Right: best-fit value of new physics parameter, $\Lambda$, as a function of the fermion mass.