Observation of ${\Lambda}_b^0$ → D⁺pπ⁻π⁻ and ${\Lambda}_b^0$ → D^*+pπ⁻π⁻ decays

Abstract

The multihadron decays ${\Lambda}_b^0$ → D+pπ−π− and ${\Lambda}_b^0$ → D^*+pπ−π− are observed in data corresponding to an integrated luminosity of 3 fb⁻¹, collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay ${\Lambda}_b^0$ → ${\Lambda}_c^{+}$π⁺π⁻π⁻ as a normalisation channel, the ratio of branching fractions is measured to be

$$ \frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {\Lambda}_c^0{\pi}^{+}{\pi}^{-}{\pi}^{-}\right)}\times \frac{\mathcal{B}\left({D}^{+}\to {K}^{-}{\pi}^{+}{\pi}^{+}\right)}{\mathcal{B}\left({\Lambda}_c^0\to {pK}^{-}{\pi}^{-}\right)}=\left(5.35\pm 0.21\pm 0.16\right)\%, $$

where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the ${\Lambda}_b^0$ → D^*+pπ⁻π⁻ and ${\Lambda}_b^0$ → D⁺pπ⁻π⁻ decays is found to be

$$ \frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{\ast +}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}\times \left(\mathcal{B}\left({D}^{\ast +}\to {D}^{+}{\pi}^0\right)+\mathcal{B}\left({D}^{\ast +}\to {D}^{+}\gamma \right)\right)=\left(61.3\pm 4.3\pm 4.0\right)\%. $$