The author applied extended BCF/BCFW rules with fermions to a set of simple electroweak processes in colliders. In such processes, there are two electroweak channels, one with a photon and the other with a Z as the in...The author applied extended BCF/BCFW rules with fermions to a set of simple electroweak processes in colliders. In such processes, there are two electroweak channels, one with a photon and the other with a Z as the internal particle. Some qualifications are needed. Compact results were obtained for tree-level NMHV amplitudes which include a quark-anti-quark pair and n gluons of the same helicity except one in the final state. In this work, we present a brief review of the BCF/BCFW rules and extensions, and list the NMHV amplitudes.展开更多
There must be electromagnetic fields created during high-energy heavy-ion collisions.Although the electromagnetic field may become weak with the evolution of the quark-gluon plasma(QGP),compared to the energy scales o...There must be electromagnetic fields created during high-energy heavy-ion collisions.Although the electromagnetic field may become weak with the evolution of the quark-gluon plasma(QGP),compared to the energy scales of the strong interaction,they are potentially important to some electromagnetic probes.In this work,we propose the coupled effect of the weak magnetic field and the longitudinal dynamics of the background medium for the first time.We demonstrate that the induced photon spectrum can be highly azimuthally anisotropic when the quarkgluon plasma is in the presence of a weak external magnetic field.On the other hand,the weak magnetic photon emission from quark-gluon plasma only leads to a small correction to the photon production rate.After hydrodynamic evolution with a tilted fireball configuration,the experimentally measured direct photon elliptic flow is well reproduced.Meanwhile,the used time-averaged magnetic field in the hydrodynamic stage is found no larger than a few percent of the pion mass square.展开更多
基金Project (No. 10425525) supported by the National Natural ScienceFoundation of China
文摘The author applied extended BCF/BCFW rules with fermions to a set of simple electroweak processes in colliders. In such processes, there are two electroweak channels, one with a photon and the other with a Z as the internal particle. Some qualifications are needed. Compact results were obtained for tree-level NMHV amplitudes which include a quark-anti-quark pair and n gluons of the same helicity except one in the final state. In this work, we present a brief review of the BCF/BCFW rules and extensions, and list the NMHV amplitudes.
文摘There must be electromagnetic fields created during high-energy heavy-ion collisions.Although the electromagnetic field may become weak with the evolution of the quark-gluon plasma(QGP),compared to the energy scales of the strong interaction,they are potentially important to some electromagnetic probes.In this work,we propose the coupled effect of the weak magnetic field and the longitudinal dynamics of the background medium for the first time.We demonstrate that the induced photon spectrum can be highly azimuthally anisotropic when the quarkgluon plasma is in the presence of a weak external magnetic field.On the other hand,the weak magnetic photon emission from quark-gluon plasma only leads to a small correction to the photon production rate.After hydrodynamic evolution with a tilted fireball configuration,the experimentally measured direct photon elliptic flow is well reproduced.Meanwhile,the used time-averaged magnetic field in the hydrodynamic stage is found no larger than a few percent of the pion mass square.
