Search for lepton-number violating processes in $B^{+}\to h^{-}{l}^{+}{l}^{+}$ decays

We have searched for the lepton-number violating processes $B^{+}\to h^{-}{\ell }^{+}{\ell }^{+}$ with $h^{-}=K^{-}/{\pi }^{-}$ and ${\ell }^{+}=e^{+}/{\mu }^{+}$, using a sample of $471\pm 3$ million $B\overline{B}$ events collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90%-confidence-level upper limits on their branching fractions $\mathcal{B}(B^{+}\to {\pi }^{-}{e}^{+}{e}^{+})<2.3\times {10}^{-8}$, $\mathcal{B}(B^{+}\to K^{-}{e}^{+}{e}^{+})<3.0\times {10}^{-8}$, $\mathcal{B}(B^{+}\to {\pi }^{-}{\mu }^{+}{\mu }^{+})<10.7\times {10}^{-8}$, and $\mathcal{B}(B^{+}\to K^{-}{\mu }^{+}{\mu }^{+})<6.7\times {10}^{-8}$.

Figure 1

An example diagram of the $\Delta L=2$ process $B^{+}\to h^{-}{\ell }^{+}{\ell }^{+}$ via $s$-channel Majorana neutrino ${\nu }_m$ production and decay.

Figure 2

The $m_{\mathrm{ES}}$ distributions for a) $B^{+}\to J/\psi (\to e^{+}{e}^{-})K^{+}$; b) $B^{+}\to J/\psi (\to {\mu }^{+}{\mu }^{-})K^{+}$; c) $B^{+}\to J/\psi (\to e^{+}{e}^{-}){\pi }^{+}$; and d) $B^{+}\to J/\psi (\to {\mu }^{+}{\mu }^{-}){\pi }^{+}$. The solid line is the total fit, the dotted line is the background, the dash-dotted line is the signal, the dashed line is the misidentified $J/\psi K^{+}$ events.

Figure 3

The $m_{\mathrm{ES}}$ distributions for a) $B^{+}\to K^{-}{e}^{+}{e}^{+}$; b) $B^{+}\to K^{-}{\mu }^{+}{\mu }^{+}$; c) $B^{+}\to {\pi }^{-}{e}^{+}{e}^{+}$; and d) $B^{+}\to {\pi }^{-}{\mu }^{+}{\mu }^{+}$. The solid line is the total fit, the dotted line is the background, the solid histogram is the signal.

Figure 4

90% C.L. upper limits on the branching fraction as a function of the mass $m_{{\ell }^{+}{h}^{-}}$ for $B^{+}\to {\pi }^{-}{\mu }^{+}{\mu }^{+}$ (dotted line), $B^{+}\to K^{-}{\mu }^{+}{\mu }^{+}$ (dash-dotted line), $B^{+}\to K^{-}{e}^{+}{e}^{+}$ (dashed line), and $B^{+}\to {\pi }^{-}{e}^{+}{e}^{+}$ (solid line).