He Yayun, Pang Long-Gang, Wang Xin-Nian
Key Laboratory of Quark & Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079, China.
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Phys Rev Lett. 2020 Sep 18;125(12):122301. doi: 10.1103/PhysRevLett.125.122301.
Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient q[over ^] in a dense QCD medium. The spatial gradient of q[over ^] perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the transverse gradient and path length of a propagating parton as shown by numerical solutions of the Boltzmann transport in the simplified form of a drift-diffusion equation. In high-energy heavy-ion collisions, this asymmetry with respect to a plane defined by the beam and trigger particle (photon, hadron, or jet) with a given orientation relative to the event plane is shown to be closely related to the transverse position of the initial jet production in full event-by-event simulations within the linear Boltzmann transport model. Such a gradient tomography can be used to localize the initial jet production position for more detailed study of jet quenching and properties of the quark-gluon plasma along a given propagation path in heavy-ion collisions.
在致密的量子色动力学（QCD）介质中，传播的部分子的横向动量展宽和能量损失由喷注输运系数q̂的时空分布决定。q̂垂直于传播方向的空间梯度会导致部分子横向动量分布出现漂移和不对称性。这种不对称性既取决于沿横向梯度的空间位置，也取决于传播部分子的路径长度，这在以漂移 - 扩散方程简化形式的玻尔兹曼输运的数值解中得到了体现。在高能重离子碰撞中，在逐事件的完整模拟中，相对于由束流和触发粒子（光子、强子或喷注）定义的平面且相对于事件平面具有给定取向的这种不对称性，被证明与初始喷注产生的横向位置密切相关，该模拟是在线性玻尔兹曼输运模型内进行的。这种梯度层析成像可用于定位初始喷注产生位置，以便更详细地研究重离子碰撞中沿给定传播路径的喷注淬火和夸克 - 胶子等离子体的性质。
