Bottomonium spectroscopy and radiative transitions involving the chi_bJ(1P,2P) states at BABAR

Understand

We use $(121\pm1)$ million $\Upsilon(3S)$ and $(98\pm1)$ million $\Upsilon(2S)$ mesons recorded by the BABAR detector at the PEP-II $e^+e^-$ collider at SLAC to perform a study of radiative transitions involving the $\chi_{b\mathrm{J}}(1P,2P)$ states in exclusive decays with $\mu^+\mu^-\gamma\gamma$ final states.

• We reconstruct twelve channels in four cascades using two complementary methods.
• In the first we identify both signal photon candidates in the Electromagnetic Calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings.
• These results include the best observational significance yet for the $\chi_{b0}(2P)\rightarrow\gamma\Upsilon(2S)$ and $\chi_{b0}(1P)\rightarrow\gamma\Upsilon(1S)$ transitions.