We present an overview of processes induced by the coherent Weizsäcker-Williams (WW) photon cloud in heavy ion collisions. Due to the rather broad energy spectrum of photons a large variety of physics topics can be addressed. At the low-energy side, there are the electromagnetic dissociation processes. We discuss the few-neutron production via giant dipole resonance excitation. A typical high energy photonuclear process that has attracted much attention is the diffractive photoproduction of vector mesons. We review the color dipole approach to coherent and incoherent diffractive photoproduction of \(J/\psi \) mesons. Finally we turn to peripheral and semicentral collisions and discuss the role of WW photons in the production of very low-\(P_T\) dileptons.

我们概述了重离子碰撞中相干的Weizsäcker-Williams（WW）光子云引起的过程。由于光子的能量谱相当宽，因此可以解决各种各样的物理问题。在低能方面，存在电磁离解过程。我们讨论了通过巨型偶极子共振激发产生的少数中子。引起广泛关注的典型高能光核过程是矢量介子的衍射光产生。我们回顾了彩色偶极子方法对\（J / \ psi \）介子的相干和非相干衍射光产生。最后，我们转向外围和半中心碰撞，并讨论WW光子在极低\（P_T \）双轻子产生中的作用。