Helicity correlations of vector bosons

强场控制 $e^+e^-$ 碰撞中 $Z$ 玻色子共振

Laser-induced selection of longitudinal $Z$ bosons in resonant $e^+e^-$ annihilation

研究强激光场对 $e^+e^-$ 碰撞中 $Z$ 玻色子共振的影响，发现非微扰处理下激光修饰改变有效碰撞运动学并打开多光子交换通道，导致共振轮廓出现强度依赖的饱和与增强，并重新分布 $Z$ 玻色子极化，高强场下可补偿电弱相互作用的固有手征不对称性。

Conservation of Helicity and SU(2) Symmetry in First Order Scattering

The structure of the spin interaction operator (SI) (the interaction that remains after space variables are integrated out) in the first order S-matrix element of the elastic scattering of a Dirac particle in a general helicity-conserving vector potential is investigated.It is shown that the conservation of helicity dictates a specific form of the SI regardless of the explicit form of the vector potential. This SI closes the SU(2) algebra with other two operators in the spin space of the particle. The directions of the momentum transfer vector and the vector bisecting the scattering angle seem…

SU(2) Symmetry and Conservation of Helicity for a Dirac Particle in a Static Magnetic Field at First Order

We investigate the spin dynamics and the conservation of helicity in the first order $S-$matrix of a Dirac particle in any static magnetic field. We express the dynamical quantities using a coordinate system defined by the three mutually orthogonal vectors; the total momentum $\mathbf{k}=\mathbf{p_f}+\mathbf{p_i}$, the momentum transfer $\mathbf{q}=\mathbf{p_f-p_i}$, and $\mathbf{l}=\mathbf{k\times q}$. We show that this leads to an alternative symmetric description of the conservation of helicity in a static magnetic field at first order. In particular, we show that helicity conservation in t…