Observation of the Λ 0 b J/ψ pπ decay

Abstract

The first observation of the Cabibbo-suppressed decay Λ 0 b J/ψpπ is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. A prominent signal is observed and the branching fraction relative to the decay mode Λ 0 b J/ψpK is determined to be

$$ \frac{\mathrm{\mathcal{B}}\left({\varLambda}_b^0\to J/\psi p{\pi}^{-}\right)}{\mathrm{\mathcal{B}}\left({\varLambda}_b^0\to J/\psi p{K}^{-}\right)} = 0.0824\pm 0.0025\ \left(\mathrm{stat}\right)\pm 0.0042\ \left(\mathrm{syst}\right). $$

A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be

$$ {\mathcal{A}}_{CP}\left({\varLambda}_b^0\to J/\psi p{\pi}^{-}\right) - {\mathcal{A}}_{CP}\left({\varLambda}_b^0\to J/\psi p{K}^{-}\right)=\left(+5.7\pm 2.4\ \left(\mathrm{stat}\right)\pm 1.2\ \left(\mathrm{syst}\right)\right)\%, $$

which is compatible with CP symmetry at the 2.2σ level.

A preprint version of the article is available at ArXiv.

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