Measurements of the X c and X b Quarkonium States in pp Collisions with the ATLAS Experiment

This thesis, which won one of the six 2015 ATLAS Thesis Awards, concerns
the study of the charmonium and bottomonium bound heavy quark bound
states. The first section of the thesis describes the observation of a
candidate for the chi_b(3P) bottomonium states. This represented the
first observation of a new particle at the LHC and its existence was
subsequently confirmed by D0 and LHCb experiments. The second part of
the thesis presents measurements of the prompt and non-prompt production
of the chi_c1 and chi_c2 charmonium states in proton-proton collisions.
These measurements are compared to several theoretical predictions and
can be used to inform the development of theoretical models of
quarkonium production.