In this paper, we propose a method to construct the decay amplitudes in the orbital (L) and spin (S) coupling scheme for particles with arbitrary spins. For the $1\to 2$ decay with only massive particles involved, the angular dependence is completely encoded in the angular momentum part, and the spins of daughter particles are coupled in the rest frame of the mother particle, which contributes only a constant factor. For the sequential decay, the total amplitude is constructed by the two $1\to 2$ amplitudes evaluated in the rest frame of their own mother particles, and then they are transformed to the common frame, usually chosen as the laboratory frame, by certain Lorentz transformations. In this way, it is easy to add the amplitudes of possible different decay chains coherently. If massless particles show up in the final states, the polarizations are expressed in helicity basis and the amplitudes are modified correspondingly.

在本文中，我们提出了一种为具有任意自旋的粒子构造轨道（L）和自旋（S ）耦合方案中的衰减幅度的方法。为了$1\to 2$仅涉及大质量粒子的衰变，角度依赖性完全编码在角动量部分中，子粒子的自旋耦合在母粒子的其余框架中，仅贡献一个常数因子。对于顺序衰减，总振幅由两个构成$1\to 2$在它们自己的母粒子的静止框架中评估振幅，然后通过某些洛伦兹变换将它们转换为公共框架，通常选择作为实验室框架。通过这种方式，很容易将可能不同的衰减链的幅度相加。如果无质量粒子出现在最终状态，则偏振以螺旋度为基础表示，并且振幅会相应地修改。