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arXiv · 1805.11192

Observation of the $χ_\mathrm{b1}$(3P) and $χ_\mathrm{b2}$(3P) and measurement of their masses

CMS Collaboration
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Abstract

The $χ_\mathrm{b1}$(3P) and $χ_\mathrm{b2}$(3P) states are observed through their $Υ$(3S) $γ$ decays, using an event sample of proton-proton collisions collected by the CMS experiment at the CERN LHC. The data were collected at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 80.0 fb$^{-1}$. The $Υ$(3S) mesons are identified through their dimuon decay channel, while the low-energy photons are detected after converting to e$^+$e$^-$ pairs in the silicon tracker, leading to a $χ_\mathrm{b}$(3P) mass resolution of 2.2 MeV. This is the first time that the $J =$ 1 and 2 states are well resolved and their masses individually measured: 10$\,$513.42 $\pm$ 0.41 (stat) $\pm$ 0.18 (syst) MeV and 10$\,$524.02 $\pm$ 0.57 (stat) $\pm$ 0.18 (syst) MeV; they are determined with respect to the world-average value of the $Υ$(3S) mass, which has an uncertainty of 0.5 MeV. The mass splitting is measured to be 10.60 $\pm$ 0.64 (stat) $\pm$ 0.17 (syst) MeV.

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CMS Collaboration. 2018-08-30. Observation of the $χ_\mathrm{b1}$(3P) and $χ_\mathrm{b2}$(3P) and measurement of their masses. https://doi.org/10.1103/physrevlett.121.092002

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