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Observation of the $\Lambda_b^0\rightarrow J/\psi p \pi^-$ decay

Abstract : The first observation of the Cabibbo-suppressed decay $\Lambda_b^0\rightarrow J/\psi p \pi^-$ is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 $\rm fb^{-1}$. A prominent signal is observed and the branching fraction relative to the decay mode $\Lambda_b^0\rightarrow J/\psi p K^-$ is determined to be $$ \frac{{\cal B}(\Lambda_b^0\rightarrow J/\psi p \pi^-)}{{\cal B}(\Lambda_b^0\rightarrow J/\psi p K^-)}=0.0824\pm0.0025\:(\text{stat})\pm0.0042\:(\text{syst}). $$ A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be $$ {\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p \pi^-)-{\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p K^-)=(+5.7\pm 2.3\:(\text{stat})\pm1.2\:(\text{syst}))\%, $$ which is compatible with CP symmetry at the $2.2\sigma$ level.
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Contributor : Sabine Starita <>
Submitted on : Wednesday, June 4, 2014 - 10:07:43 AM
Last modification on : Friday, November 20, 2020 - 3:30:14 PM

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R. Aaij, Y. Amhis, S. Barsuk, M. Borsato, O. Callot, et al.. Observation of the $\Lambda_b^0\rightarrow J/\psi p \pi^-$ decay. Journal of High Energy Physics, Springer, 2014, 7, pp.103. ⟨10.1007/JHEP07(2014)103⟩. ⟨in2p3-00999792⟩



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