An Impact of Parton Distribution Functions on Open Heavy Flavor Azimuthal Angular Correlations in Pb-Pb Collisions at $\sqrt{s_{NN}}$ = 5.5 TeV

Abstract: In this paper, we investigate the impact of modern free parton distribution functions and nuclear parton distribution functions on the azimuthal angular correlation of open heavy flavor hadrons in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.5 TeV using PYTHIA8 + Angantyr model. The method involves a transverse momentum ($p_{\rm{T}}$) differential assessment of azimuthal angular correlations between prompt $\rm{D^0-\bar{D}^0}$ and $\rm{B-\bar{B}}$. By analyzing the $p_{\rm{T}}$-dependent behavior of these correlations, we probe the interplay between different production mechanisms and assess the impact of parton distribution functions on heavy-flavor hadron production dynamics. Our results indicate that nuclear parton distribution functions significantly modify both near-side and away-side peaks of the azimuthal correlation distribution compared to the default PYTHIA8 baseline, particularly at low $p_{\rm{T}}$. The near-side double-peak structure suggests contributions from next-to-leading order (NLO) processes, such as gluon splitting, and its presence is strongly correlated with the number of hard multi-partonic interactions. Additionally, by quantitatively comparing the change in correlation widths across various PDF settings, we comment on the role of nuclear parton distribution functions in heavy-quark thermalization in heavy-ion collisions. This comprehensive study of azimuthal correlations enhances our understanding of initial-state conditions and heavy-flavor production dynamics in nuclear collisions.