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
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

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