Pair production of dark particles in meson decays

Abstract

Rare decays of $K$ and $B$ mesons provide a powerful probe of dark sectors with light new particles. We show that the pair production of $O(100\mathrm{MeV})$ dark states can be probed with the decays of $K_L$ mesons, owing to the enhanced two-body kinematics, $K_L\to X_1{X}_2$ or $X_2{X}_2$. If either or these two particles is unstable, e.g. $X_2\to X_1{\pi }^0$, $X_2\to X_1\gamma$ or $X_{1,2}\to \gamma \gamma$, such decays could easily mimic $K_L\to {\pi }^0\nu \overline{\nu }$ signatures, while not being ruled out by the decays of charged kaons. We construct explicit models that have enhanced $K_L$ decay signatures, and are constrained by the results of the KOTO experiment. We note that recently reported excess events can also be accommodated while satisfying all other constraints ($B$ decays, colliders, beam dumps). These models are based on the extensions of the gauge and/or scalar sector of the theory. The lightest of $X_{1,2}$ particles, if stable, could constitute the entirety of dark matter.

25 pages, 9 figures, 1 table, v2: KOTO signal efficiency plots added. Accepted for publication in PRD

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Cited by in corpus (8)

• Probing lepton number violating interactions in rare kaon decays
• Searching for Elusive Dark Sectors with Terrestrial and Celestial Observations
• Flavor-changing light bosons with accidental longevity
• Search for the Pair Production of Dark Particles $X$ with $K_L^0\to XX$, $X\to \gamma \gamma$
• Dark boson mediation of the ${\pi }^0\to \gamma e^{+}{e}^{-}$ decay
• New Physics Searches at Kaon and Hyperon Factories
• Recent progress in decays of $b$ and $c$ hadrons
• Semi-Visible Dark Photon Phenomenology at the GeV Scale