Medium modifications of the photon-tagged jet fragmentation function in high-energy heavy-ion collisions

Based on a multiphase transport model, medium modifications of prompt photon-tagged jet fragmentation function are investigated by comparing prompt photon-tagged hadron azimuthal correlation in $\text{Au}+\text{Au}$ collisions (0%–40%) with that in $p+p$ collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. The measured modification factor $I_{AA}$ increases with the increasing integration range of the away side, which reveals a medium-modified jet shape in which the medium enhancement of soft particles is preferentially located far away from the jet axis. $I_{AA}$ largely results from strong interactions between jets and partonic matter. However, both hadronization of coalescence and hadronic rescatterings play certain roles to modify the $I_{AA}$. These behaviors reflect a dynamical evolution of modifications of the prompt photon-tagged jet fragmentation function in high-energy heavy-ion collisions.

Figure 1

(a)–(f) The $\gamma$-tagged hadron azimuthal correlations for different $\xi$ bins in $p+p$ collisions and $\text{Au}+\text{Au}$ collisions (0%–40%) at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. The AMPT results are shown by histograms, while experimental data are shown by circles for which error bars indicate the statistical uncertainties only and the systematic uncertainties are not included [18].

Figure 2

The $\gamma$-tagged jet fragmentation functions for $p+p$ collisions and $\text{Au}+\text{Au}$ collisions (0-40%) at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV. The AMPT results are shown by curves, while experimental data are shown by circles for which error bars indicate the statistical uncertainties only and the systematic uncertainties are not included [18].

Figure 3

The $I_{AA}$ for full away side ($|\Delta \varphi -\pi |<\pi /2$) and for two restricted away-side integration ranges ($|\Delta \varphi -\pi |<\pi /3$ and $|\Delta \varphi -\pi |<\pi /6$). The AMPT results are shown by curves, while experimental data are shown by symbols for which error bars indicate the statistical uncertainties only and the systematic uncertainties are not included [18]. Some points are slightly shifted for clarity.

Figure 4

(a)–(f) The $\gamma$-tagged parton azimuthal correlations for in the initial state (dashed) and after the process of parton cascade (solid) for different $\xi$ bins in $\text{Au}+\text{Au}$ collisions (0%–40%) at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV.

Figure 5

The $I_{AA}$ for full away side ($|\Delta \varphi -\pi |<\pi /2$) at or after different evolution stages. The AMPT results are shown by curves, while experimental data are shown by circles for which error bars indicate the statistical uncertainties only and the systematic uncertainties are not included [18].