Search for $B$ mesogenesis at BaBar

A new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic $B$-meson decays into a baryon and a dark-sector antibaryon (${\psi }_D$) with branching fractions accessible at $B$ factories. We present a search for $B\to \mathrm{\Lambda }{\psi }_D$ decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying $B$ meson and requiring the presence of a single $\mathrm{\Lambda }$ baryon in the remaining particles. No significant signal is observed, and bounds on the $B\to \mathrm{\Lambda }{\psi }_D$ branching fraction are derived in the range $0.13–5.2\times {10}^{-5}$ for $1.0<m_{{\psi }_D}<4.2\mathrm{GeV}/c^2$. These results set strong constraints on the parameter space allowed by the theory.

Figure 1

Illustration of the $B$-mesogenesis mechanism. Figure taken from Ref. [6].

Figure 2

Distributions of the energy-substituted mass, $m_{\mathrm{ES}}$ (top), and the reconstructed $\mathrm{\Lambda }$ mass, $m_{\mathrm{\Lambda }}$ (bottom), for data (points), signal MC for $m_{{\psi }_D}=2.0\mathrm{GeV}/c^2$ (red histogram) and inclusive background MC predictions (stacked histograms, no corrections applied). The normalization of the signal events is arbitrary.

Figure 3

The distribution of the BDT score after applying all other selection criteria for data (points), signal MC for $m_{{\psi }_D}=2.0\mathrm{GeV}/c^2$ (red histogram), and inclusive background MC predictions (stacked histograms, no corrections applied). The normalization of the signal events is arbitrary.

Figure 4

The distribution of the ${\psi }_D$ mass ($m_{{\psi }_D}$) after applying all selection criteria for data (points), signal MC for $m_{{\psi }_D}=2.0\mathrm{GeV}/c^2$ (red histogram), and inclusive background MC predictions (stacked histograms). The normalization of the signal events is arbitrary.

Figure 5

Upper limits on the $B^0\to {\psi }_D\mathrm{\Lambda }$ branching fraction at a 90% CL, together with previous constraints [11]. The light blue and orange [orange-only] region shows the values of the $B^0\to {\psi }_D\mathrm{\Lambda }$ branching fraction allowed to successfully generate $B$ mesogenesis for the ${\mathcal{O}}_{us}^1=({\psi }_{D}b)(us)$ [${\mathcal{O}}_{us}^2=({\psi }_{D}s)(ub)$ and ${\mathcal{O}}_{us}^3=({\psi }_{D}u)(sb)$] effective operators [6].