Speaker
Description
Quarkonia are bound states of heavy quark--antiquark pairs. Due to their large mass, heavy quarks production mechanism takes place at hard scales of QCD, while the formation of the bound states involves soft QCD scales. Quarkonia are therefore sensitive to both perturbative and non-perturbative aspects of QCD.
In addition, their measurement in p--Pb collisions provides information on cold nuclear matter effects, such as nuclear shadowing or interaction with comoving particles.
Recent measurements reveal that $J/\psi$ yields increase with charged-particle multiplicity in pp and p--Pb collisions at the LHC. Different mechanisms were proposed to explain this observation. One of them is the influence of multiple parton interactions in the initial state of the collision. Measurements of the excited charmonium states, e.g $\psi(2S)$, as a function of charged-particle multiplicity are essential to disentangle the impact of possible final-state effects.
This poster presents the measurement of charmonium yields in pp collisions at $\sqrt{s}$ = 13 TeV and p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV as a function of charged-particle multiplicity, measured at central rapidity ($|\eta|<1.0$). $J/\psi$ and $\psi(2S)$ are reconstructed in their dimuon decays within $2.5
