Correlations between heavy mesons and the creation of the charmonia, bottomonia, and $B_c$ mesons in high energy $pp$ collisions

TL;DR

This paper demonstrates that initial heavy-quark pair production mechanisms imprint distinct azimuthal and momentum correlations on both open and hidden heavy-flavour observables in high-energy $pp$ collisions. It combines the EPOS4HQ event generator with a quantum density-matrix / Wigner-density formalism to model quarkonium formation and $B_c$ production, capturing how different production channels (flavor creation, flavor excitation, gluon splitting) contribute to $p_T$ spectra and rapidity distributions across charmonium, bottomonium, and $B_c$ states. The approach reproduces experimental data for $D\bar D$, $B\bar B$, prompt quarkonia, and $B_c$ spectra, and provides insight into the spatial distribution of heavy-quark creation via the inferred source parameters and pomeron topology. Overall, the work offers a unified framework linking production kinematics, quantum-state formation, and spatial structure in $pp$ collisions, with implications for interpreting HF observables and for constraining parton-level spatial distributions.

Abstract

The different QCD processes, which can produce a heavy quark-antiquark ($Q\bar Q$) pair, induce different correlations between the heavy quarks. Employing the EPOS4HQ event generator we study the consequences of these correlations and compare the calculation with experimental results on open and hidden heavy flavour mesons, measured in proton-proton (pp) collisions at RHIC and LHC energies. We find that the measured correlations between heavy mesons are a direct image of the different production mechanisms, which contribute also in a different way to the transverse momentum distribution of open and hidden heavy flavour mesons. The latter are calculated in a Wigner density approach which also enables to reproduce quantitatively the measured $B_c$ spectra. This agreement allows conclusions on the spatial distribution of the heavy quark creation processes.

Figures (20)

• Figure 1: The three production mechanisms for heavy quark pairs. From left to right: flavor excitation, flavor creation, and gluon splitting. For details we refer to the text.
• Figure 2: The correlation between the rapidities of $c$ and $\bar{c}$ from different processes in pp collisions at $\sqrt{s}=5.02 ~ \rm TeV$.
• Figure 3: The correlation between $p_T$ of $c$ and $\bar{c}$ from different processes in pp collisions at $\sqrt{s}=5.02 ~ \rm TeV$ and central rapidity $|y|<1$.
• Figure 4: The normalized distribution of the total rapidity of $c$ and $\bar{c}$ (upper), $b$ and $\bar{b}$ (lower) for different processes in pp collisions at $\sqrt{s}=5.02~\rm TeV$.
• Figure 5: Same as Fig. \ref{['fig.y1y2']} for $b\bar{b}$ pairs.