Speaker
Description
I will present the implementation of a fully automated quarkonium parton shower in Herwig 7 based on non-relativistic QCD factorisation with explicit spin and colour projections. The framework incorporates both colour-singlet and colour-octet production channels, including gluon fragmentation and diquark production, and combines perturbative short-distance coefficients with non-perturbative NRQCD matrix elements to describe heavy-quark bound-state formation. Splitting functions for S-, P- and D-wave quarkonium states are derived and embedded in the angular-ordered shower evolution, with spin correlations, polarisation effects and feed-down contributions retained throughout. I will discuss the structure of the implementation and its phenomenological performance, including comparisons with LHC data.