$B\to K+$invisible, dark matter, and $CP$ violation in hyperon decays

Abstract

Recently the Belle II Collaboration has reported a measurement of the $B^{+}\to K^{+}\nu \bar{\nu }$ rate that is higher than the standard-model expectation. Since the emitted neutrinos are unobserved, the excess could be due to the $B^{+}$ decaying into a $K^{+}$ and a dark-matter pair. We entertain this possibility in a two-Higgs-doublet model supplemented with a real singlet scalar boson acting as the dark matter. This model also accommodates strangeness-changing interactions providing new sources of $CP$ violation which can affect hyperon and kaon nonleptonic transitions. We find that the resulting $CP$ violation in the hyperon sector can be significant, reaching the current empirical bounds, after taking into account constraints from kaon mixing and decay and from dark-matter relic-density data and direct searches including the Migdal effect. We demonstrate that the hyperon and kaon processes are complementary probes of this new-physics scenario. Its prediction for sizable hyperon $CP$ violation is potentially testable in ongoing experiments, such as BESIII, Belle II, and LHCb, and in next-generation ones like PANDA and at the Super Tau Charm Facility.

24 pages, 7 figures, slightly expanded, matches journal version

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Cited by in corpus (6)

• Light dark-matter window constrained by \boldmath$K^{+}\to {\pi }^{+}$$+$$/E$
• CP violation in the hyperon decays $\Sigma \to N\pi$
• Resonant ALP-Portal Dark Matter Annihilation as a Solution to the $B^{\pm }\to K^{\pm }\nu \bar{\nu }$ Excess
• Scrutinizing dark-matter scenarios with $B\to (K,K^{\ast })\bar{\nu }\nu$ decays
• Probing vector- vs scalar-mediator dark-matter scenarios in $B\to (K,K^{\ast })M_X$ decays
• Dark Matter emission at Belle II and NA62 in Minimal Flavor Violation framework