A search for baryogenesis and dark matter in $B^+ \to \Lambda_c^+ + {\rm invisible}$ decays

A mechanism of baryogenesis and dark matter production via $B$-meson oscillations and decays has recently been proposed to explain the observed dark matter abundance and matter-antimatter asymmetry in the universe. This mechanism introduces a light dark sector particle ($\psi_D$) with a non-zero baryonic charge. We present a search for this new state in $B^+ \to \Lambda_c^+ \, \psi_D$ decays using data collected at the $\Upsilon(4S)$ resonance by the BABAR detector at SLAC, corresponding to an integrated luminosity of $431.0 \rm{~fb}^{-1}$. The search leverages the full reconstruction of the $B^-$ meson in $\Upsilon(4S) \to B^+B^-$ decays, accompanied by the reconstruction of a $\Lambda_c^+$, to infer the presence of $\psi_D$. No significant signal is observed, and limits on the $B^+ \to \Lambda_c^+ \, \psi_D$ branching fraction are set at the level of $1.6 \times 10^{-4}$ at 90% confidence level for $0.94 < m_{\psi_D} < 2.99$ GeV. These results set strong constraints on the parameter space allowed by $B$-meson baryogenesis.