Disentangling new physics in $K\to \pi \bar{\nu }\nu$ and $B\to K(K^{\ast })\bar{\nu }\nu$ observables

Abstract

We investigate the possibility of disentangling different new physics contributions to the rare meson decays $K\to \pi +/E$ and $B\to K(K^{\ast })+/E$ through kinematic distributions in the missing energy $/E$. We employ dimension-$6$ operators within the Low-Energy Effective Field Theory (LEFT), identifying the invisible part of the final state as either active or sterile neutrinos. Special emphasis is given to lepton-number violating (LNV) operators with scalar and tensor currents. We show analytically that contributions from scalar, vector, and tensor quark currents can be uniquely determined from experimental data of kinematic distributions. In addition, we present new correlations of branching ratios for $K$ and $B$-decays involving scalar and tensor currents. As there could a priori also be new invisible particles in the final states, we include dark-sector operators giving rise to two dark scalars, fermions, or vectors in the final state. In this context, we present new calculations of the inclusive decay rate $B\to X_s+/E$ for dark operators. We show that careful measurements of kinematic distributions make it theoretically possible to disentangle the contribution from LEFT operators from most of the dark-sector operators, even when multiple operators are contributing. We revisit sum rules for vector currents in LEFT and show that the latter are also satisfied in some new dark-physics scenarios that could mimic LEFT. Finally, we point out that an excess in rare meson decays consistent with a LNV hypothesis would point towards highly flavor non-democratic physics in the UV, and could put high-scale leptogenesis under tension.

v2: Figures 1 and 2 have been updated to reflect the new NA62 results

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Cited by in corpus (14)

• The decay $B\to K+\nu +\bar{\nu }$ at Belle II and a massless bino in R-parity-violating supersymmetry
• Impact of new invisible particles on $B\to K^{(\ast )}{E}_{\mathrm{miss}}$ observables
• $B\to K+$invisible, dark matter, and $CP$ violation in hyperon decays
• Observation of the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay and measurement of its branching ratio
• Neutrinoless Double Beta Decay from Scalar Leptoquarks: Interplay with Neutrino Mass and Flavor Physics
• Light dark-matter window constrained by \boldmath$K^{+}\to {\pi }^{+}$$+$$/E$
• Correlating $0\nu \beta \beta$ decays and flavor observables in leptoquark models
• Charged lepton flavor violating decays with a pair of light dark matter and muonium invisible decay
• Multi-Component Dark Matter from Minimal Flavor Violation
• Dark Matter emission at Belle II and NA62 in Minimal Flavor Violation framework
• Belle II Constraints on the Non-Minimal Universal Extra Dimensional Model
• Characterizing Dark Bosons at Chiral Belle
• Feasibility Study of Lepton Number Violation in Rare $B$ and $K$ Meson Decays
• First search for $B\to X_s\nu \bar{\nu }$ decays