Quarkonia production has been a long-standing puzzle in particle
physics. These are mesons which contain quarks of the same flavour,
for example J/ψ. The polarisation measurement of J/ψ is expected to
have significant transverse polarisation at large pT, but has been
experimentally observed to be consistent with zero. Hard production of
onia processes using NRQCD formalism are available in the Pythia8
framework. However, these processes alone cannot fully describe the
data; LHCb and CMS have shown with normalised cross section
measurements of z = pT (J/ψ)/pT (jet) that J/ψ’s are produced softer
than expected. Hence the need to incorporate onia production within the
parton shower.

Therefore, the aim of this project is to incorporate the main splitting
functions of various quarkonia into Pythia8. Then compare results with
Ariadne and LHCb/CMS data as cross checks.

Naomi Cooke
June, 2021 to January, 2022