We present a study of the directed flow v₁ for D mesons discussing both the impact of initial vorticity and electromagnetic field. Recent studies predicted that v₁ for D mesons is expected to be surprisingly much larger than that of light charged hadrons; we clarify that this is due to a different mechanism leading to the formation of a directed flow with respect to the one of the bulk matter at both relativistic and non-relativistic energies. We point out that the very large v₁ for D mesons can be generated only if there is a longitudinal asymmetry between the bulk matter and the charm quarks and if the latter have a large non-perturbative interaction in the QGP medium. A quite good agreement with the data of STAR and ALICE is obtained if the diffusion coefficient able to correctly predict the R_AA(p_T), v₂(p_T) and v₃(p_T) of D meson is employed. Furthermore, the mechanism for the build-up of the v₁(y) is associated to a quite small formation time that can be expected to be more sensitive to the initial high-temperature dependence of the charm diffusion coefficient.

We discuss also the splitting of v₁ for D⁰ and \( {\overline{D}}^0 \) due to the electromagnetic field that is again much larger than the one observed for charged particles and in agreement with the data by STAR that have however still error bars comparable with the splitting itself, while at LHC standard electromagnetic profile assuming a constant conductivity is not able to account for the huge splitting observed.

我们对D介子的定向流v ₁进行了研究，讨论了初始涡度和电磁场的影响。最近的研究预测，v ₁为d介子预计是令人惊讶地比的光强子带电大得多; 我们澄清这是由于不同的机制导致相对论能量和非相对论能量都相对于大块物质之一形成了定向流。我们指出了非常大的v ₁的d仅当块状物质和夸克夸克之间存在纵向不对称性，并且夸克在QGP介质中具有较大的非扰动相互作用时，才会产生介子。如果采用能够正确预测D介子的R _AA（p _T），v ₂（p _T）和v ₃（p _T）的扩散系数，则可以与STAR和ALICE数据获得很好的一致性。此外，建立v ₁（y）与相当短的形成时间有关，可以预期该形成时间对魅力扩散系数的初始高温依赖性更加敏感。

我们还讨论的分裂v ₁为d ⁰和\（{\划线{d}} ^ 0 \）由于电磁场再次比带电粒子和与由STAR数据协议中观察到的一个大得多的然而，它们仍然具有与分裂本身相当的误差线，而在LHC标准电磁曲线中，假设电导率恒定不能解释观察到的巨大分裂。