Measurements of the Branching Fractions of Λc+ → p π− π+, Λc+ → p K− K+, and Λc+ → p π− K+

The ratios of the branching fractions of the decays Λc+ → p π− π+, Λc+ → p K− K+, and Λc+ → p π− K+ with respect to the Cabibbo-favoured Λc+ → p K− π+ decay are measured using proton-proton collision data collected with the LHCb experiment at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity of 1.0 fb^−1: B(Λc+ → p π− π+)/B(Λc+ → p K− π+) = (7.44 ± 0.08 ± 0.18)%, B(Λc+ → p K− K+)/B(Λc+ → p K− π+) = (1.70 ± 0.03 ± 0.03)%, B(Λc+ → p π− K+)/B(Λc+ → p K− π+) = (0.165 ± 0.015 ± 0.005)%, where the uncertainties are statistical and systematic, respectively. These results are the most precise measurements of these quantities to date. When multiplied by the world-average value for B(Λc+ → p K− π+), the corresponding branching fractions are B(Λc+ → p π− π+) = (4.72 ± 0.05 ± 0.11 ± 0.25) × 10^−3, B(Λc+ → p K− K+) = (1.08 ± 0.02 ± 0.02 ± 0.06) × 10^−3, B(Λc+ → p π− K+) = (1.04 ± 0.09 ± 0.03 ± 0.05) × 10^−4, where the final uncertainty is due to B(Λc+ → p K− π+).