Measurements of the production of P-wave charmonium states through radiative decays at the ATLAS experiment

Understanding of the production of P-wave charmonium states is a significant bottleneck in the understanding of charmonium production as a whole. Current theoretical calculations are limited in their ability to model the production and decay of these states. We present new measurements of the double-differential production cross-sections of the three chi_cJ spin states separately, extending upon previous measurements in precision, kinematic reach, and number of measurements. The relative production cross-sections of the various chi_c states through prompt and non-prompt production modes are explored as a function of transverse momentum, as well as the fraction of the total J/psi production which occurs via chi_c feed-down. Results are compared with latest theoretical predictions from a variety of theoretical approaches. A competitive measurement of the branching fraction of B+ --> chi_c1 + K+ is also presented.