Study of $B_c^{+}\to {\chi }_c{\pi }^{+}$ decays

Abstract

A study of $B_c^{+}\to {\chi }_c{\pi }^{+}$ decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9fb${}^{-1}$. The decay $B_c^{+}\to {\chi }_{c2}{\pi }^{+}$ is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the $B_c^{+}\to J/\psi {\pi }^{+}$ decay is measured to be $$\frac{{\mathcal{B}}_{B_c^{+}\to {\chi }_{c2}{\pi }^{+}}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi }^{+}}}=0.37\pm 0.06\pm 0.02\pm 0.01,$$ where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the ${\chi }_c\to J/\psi \gamma$ branching fraction. No significant $B_c^{+}\to {\chi }_{c1}{\pi }^{+}$ signal is observed and an upper limit for the relative branching fraction for the $B_c^{+}\to {\chi }_{c1}{\pi }^{+}$ and $B_c^{+}\to {\chi }_{c2}{\pi }^{+}$ decays of $$\frac{{\mathcal{B}}_{B_c^{+}\to {\chi }_{c1}{\pi }^{+}}}{{\mathcal{B}}_{B_c^{+}\to {\chi }_{c2}{\pi }^{+}}}<0.49$$ is set at the 90\% confidence level.

arXiv comment30 pages, 5 figures, All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-039.html (LHCb public pages)

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