Recent Results from BABAR: Dark Matter, Axion-like Particles and Heavy Neutral Leptons, a contribution to the 2023 Electroweak session of the 57th Rencontres de Moriond

Abstract

Three independent searches for new physics using data collected at BABAR are presented. Firstly, two searches for dark matter and baryogenesis: $B^0\to \Lambda +{\psi }_D$ and $B^{+}\to p+{\psi }_D$ are detailed, where ${\psi }_D$ is a new dark fermion. Neither signal is observed and new upper limits on the branching fractions, at the 90 $\%$ confidence level (C.L), are placed at $\mathcal{O}(10^{-5}-10^{-6})$ across the mass range $1.0<m_{{\psi }_D}<4.3$ GeV/c${}^2$. Secondly, new limits on the coupling, $g_{aW}$, of an axion-like particle ($a$) to the $W$ boson, at the 90 $\%$ C.L, are presented at $\mathcal{O}(10^{-5})$ GeV${}^{-1}$ for $a$ masses in the mass range 0.175 $<m_a<$ 4.78 GeV/c${}^2$. Thirdly, a model-independent search for heavy neutral leptons (HNL) found new upper limits at the 95 $\%$ C.L on the extended Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix element, $|U_{\tau 4}{|}^2$, which depend on the HNL mass hypothesis and vary from $2.31\times 10^{-2}$ to $5.04\times 10^{-6}$, across the mass range $100<m_4<1300$ MeV/c${}^2$, with more stringent limits on higher HNL masses.

Comments: contribution to the 2023 Electroweak session of the 57th Rencontres de Moriond. 6 pages 4 figures