Probing the in-medium $$P_T$$-broadening by $$\gamma $$+HF angular de-correlations

Abstract

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 $$\gamma +$$ HF in nucleus-nucleus collisions as a new probe of the in-medium $$P_T$$ -broadening effect. The initial production of $$\gamma + $$ 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 $$\Delta \phi _{\gamma D}\sim \pi $$ and enhancement at $$\Delta \phi _{\gamma D}<2.8$$ in $$\gamma + $$ 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 $$\gamma + $$ D angular distribution are sensitive to the selection cut of D meson $$p_T$$ . Furthermore, by constructing the 2D ( $$x_{J}^{\gamma D}, \Delta \phi _{\gamma D}$$ ) 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 $$\gamma + $$ D observable simultaneously. Additionally, we find weaker angular de-correlations of $$\gamma + $$ B compared to $$\gamma + $$ D which may be helpful to understand the mass hierarchy in heavy-ion collisions. Finally, the nuclear modification of $$\Delta \phi _{\gamma D}$$ distributions in central 0–10% Au + Au collisions at RHIC energy is provided for completeness.