Probing the in-medium P${}_T$-broadening by γ+HF angular de-correlations

Angular correlations between vector boson and heavy flavors (HF) are potentially new effective tools to gain insight into the partonic interactions in the quark-gluon plasma (QGP). In this paper, we present the theoretical study of the azimuthal angular de-correlations of γ+HF in nucleus-nucleus collisions as a new probe of the in-medium P${}_T$-broadening effect. The initial production of γ+HF in p + p is generated by SHERPA which matches the next-to-leading hard processes with parton shower. The in-medium heavy quark evolution is implemented by a Monte Carlo Langevin simulation, which takes into account the collisional and radiative energy loss. We observe considerable suppression at Δϕ${}_{\gamma D}$ ∼ π and enhancement at Δϕ${}_{\gamma D}$< 2.8 in γ+D azimuthal angular distribution in 0-10% Pb + Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV compared to the p + p baseline, which indicates evident in-medium P${}_T$-broadening of charm quarks. We also find that the overall modification patterns of γ+D angular distribution are sensitive to the selection cut of D meson p${}_T$. Furthermore, by constructing the 2D (x${}_J^{\gamma D}$, Δϕ${}_{\gamma D}$) correlation diagram, it's possible to display the respective impact of the two aspects of jet quenching, energy loss and P${}_T$-broadening, on the final-state γ+D observable simultaneously. Additionally, we find weaker angular de-correlations of γ+B compared to γ+D which may be helpful to understand the mass hierarchy in heavy-ion collisions. Finally, the nuclear modification of Δϕ${}_{\gamma D}$ distributions in central 0-10% Au + Au collisions at RHIC energy is provided for completeness.