Speaker
Description
$~~~~$PHENIX experiment group points out that in the measurements of the $\pi^0$ nuclear modification factor $R_{dAu}^{\pi^0}$, $\langle N_{\rm coll} \rangle$ can be biased by the event-selection [1], which can be effectively reduced by using the direct $\gamma$ yield at large $p_{\rm T}$ to determine the $\langle N_{\rm coll}^{\gamma} \rangle = {\rm Y}_{dAu}^{\gamma^{\rm dir}}/{\rm Y}_{pp}^{\gamma^{\rm dir}}$ [2]. Utilizing the $\langle N_{\rm coll}^{\gamma} \rangle$ provided by PHENIX, the $\pi^0$ suppression is studied within a next-to-leading-order perturbative QCD parton model [3] incorporating the medium-modified parton fragmentation functions [4]. This study is under the assumption that the quark-gluon plasma (QGP) is produced, and its evolution can be described by hydrodynamics in $d$-$Au$ collisions at $\sqrt{s_{\rm NN}}$=200 GeV. The initial conditions and space-time evolution of the matter created in $d$-$Au$ collisions are provided by the superSONIC hydrodynamic model simulations [5,6] and parton energy loss in such a small medium is described by the high-twist (HT) approach [7]. The jet transport coefficient $\hat{q}/T^3(T)$ in this HT approach is extracted with the information field (IF)-Bayesian inference approach from all existing experimental data on single-inclusive hadron, dihadron, and $\gamma$-hadron spectra in heavy-ion collisions at RHIC and the LHC energies [8,9]. When only including the cold nuclear matter effect, the $\langle R_{dAu}^{\pi^0} \rangle$ averaged over $7.5 References
[1] J. Adam et al. [ALICE], Phys. Rev. C 91 (2015) no.6, 064905
[2] N. J. Abdulameer et al. [PHENIX], [arXiv:2303.12899 [nucl-ex]].
[3] J. F. Owens, Rev. Mod. Phys. 59 (1987), 465
[4] X. N. Wang, Phys. Rev. C 70 (2004), 031901
[5] P. Romatschke, Eur. Phys. J. C 75 (2015) no.7, 305
[6] R. D. Weller and P. Romatschke, Phys. Lett. B 774 (2017), 351-356
[7] X. f. Guo and X. N. Wang, Phys. Rev. Lett. 85 (2000), 3591-3594
[8] M. Xie, W. Ke, H. Zhang and X. N. Wang, Phys. Rev. C 108 (2023) no.1, L011901
[9] M. Xie, W. Ke, H. Zhang and X. N. Wang, [arXiv:2208.14419 [hep-ph]].
