The poster reports the first observation of the $B^0_{(s)} \to J/\psi p \overline{p}$ decays and precise $B^0_{(s)}$ mass measurements. The analysis is perfomed using proton-proton collision data corresponding to an integrated luminosity of $5.2{\text{fb}}^{-1}$, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to OZI or Cabibbo suppression. The measured branching fractions are \begin{align*} \mathcal{B}(B^0 \to J/\psi p \overline{p}) &= (4.51\pm 0.40\; \text{(stat)} \pm 0.44\; \text{(syst)}) \times 10^{-7}, \\ \mathcal{B}(B^0_s \to J/\psi p \overline{p}) &= (3.58\pm 0.19\; \text{(stat)} \pm 0.33\; \text{(syst)}) \times 10^{-6}. \end{align*} For the $B^0_s$ meson the result is much higher than the expected value of $ {\cal O} (10^{-9})$. The small available phase space in these decays also allows for the most precise single measurement of both the $B^0$ mass as ${5279.74 \pm 0.30\; ({\rm stat})\pm 0.10\; ({\rm syst})}$~MeV, and the $B^0_s$ mass as ${5366.85 \pm 0.19\; ({\rm stat})\pm 0.13\; ({\rm syst})}$~MeV.
In 36 pb$^{-1}$ of $pp$ collisions at a centre-of-mass energy $\sqrt{s}$ = 7 TeV, we observe for the first time the decay $\bar{B}^0_s \to D^0 K^{*0}$. The $\bar{B}^0_s \to D^0 K^{*0}$ decay mode is a potentially dangerous background for the Cabibbo suppressed decay $B^0 \to \bar{D}^0 K^{*0}$ used in the measurement of the CKM angle $\gamma$. A clear signal of 34.5$\pm$6.9 events is obtained with a statistical significance over 9 standard deviations and we measure its branching ration relative to the $\bar{B}^0 \to D^0\rho^0$ branching ratio.