Observation of the decay ${\Lambda }_b^0\to \psi (2S)p{\pi }^{-}$

Abstract

The Cabibbo-suppressed decay ${\Lambda }_b^0\to \psi (2S)p{\pi }^{-}$ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9fb${}^{-1}$ of integrated luminosity at centre-of-mass energies of 7, 8 and 13TeV, respectively. The $\psi (2S)$ mesons are reconstructed in the ${\mu }^{+}{\mu }^{-}$ final state. The~branching fraction with respect to that of the ${\Lambda }_b^0\to \psi (2S)p{K}^{-}$ decay mode is measured to be $$\frac{\mathcal{B}\left({\Lambda }_b^0\to \psi (2S)p{\pi }^{-}\right)}{\mathcal{B}\left({\Lambda }_b^0\to \psi (2S)p{K}^{-}\right)}=\left(11.4\pm 1.3\pm 0.2\right)\%,$$ where the first uncertainty is statistical and the second is systematic. The $\psi (2S)p$ and $\psi (2S){\pi }^{-}$ mass spectra are investigated and no evidence for exotic resonances is found.

arXiv comment16 pages, 2 figures. All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-022.html

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