Probe charmonium-nucleon interactions in high energy proton-proton collisions

Abstract

We investigate charmonium production and the charmonium-nucleon correlation function in pp collisions using the EPOS4+CATS framework. For the first time, the emission source of charmonium-proton pairs is dynamically generated and found to be non-Gaussian. This enables a femtoscopic extraction of the charmonium-proton interaction directly from experimental correlation functions. Both ground and excited charmonium states are included. We found that the excited states induce sizable uncertainties even negative in the observed prompt $J/ψ$-proton correlation through feed-down effects, reflecting their stronger interactions.

Figures (5)

• Figure 1: The interaction potential of $J/\psi-N$ from HAL QCD with spin-3/2 (red) and 1/2 (blue) state and $J/\psi-N$ from the QCDME with perturbative chromoelectric polarizability $\alpha_{J/\psi}=0.2~\rm GeV^{-3}$ (orange-dashed) and non-perturbative one $\alpha_{J/\psi}=1.6~\rm GeV^{-3}$ (orange-solid).
• Figure 2: Transverse-momentum distribution at forward rapidity (upper panel) and rapidity distribution (lower panel) of prompt $J/\psi$ in pp collision at $\sqrt{s}=13~\rm TeV$. The experimental data is from ALICE ALICE:2017legALICE:2021dtt and LHCb LHCb:2015foc. The uncertainty band arises from the variation of the width $\sigma_{c\bar{c}}$.
• Figure 3: The normalized emission source of charmonium-nucleon from EPOS4 in pp collisions at 13TeV. The black dashed line is the Gaussian source fit with $r_0=1.006~\rm fm$, which gives the same rms radius.
• Figure 4: Correlation function between direct $J/\psi$ and proton in pp collisions at 13 TeV. The black line is the result using the HAL QCD interaction while orange solid and dashed lines are that with interactions from the QCDME, respectively.
• Figure 5: Correlation functions between the direct $J/\psi$, $\chi_c$, $\psi(2S)$, prompt $J/\psi$ and the proton in pp collisions at 13 TeV. The interaction potentials are taken from the QCD multipole expansion Eides:2015dtrPolyakov:2018aey. The left panel corresponds to perturbative chromoelectric polarizabilities, while the right panel shows results using nonperturbative values.