Model-independent constraints on the shape parameters of dilepton angular distributions

Understand

The coefficients determining the dilepton decay angular distribution of vector particles obey certain positivity constraints and a rotation-invariant identity.

• These relations are a direct consequence of the covariance properties of angular momentum eigenstates and are independent of the production mechanism.
• The Lam-Tung relation can be derived as a particular case, simply recognizing that the Drell-Yan dilepton is always produced transversely polarized with respect to one or more quantization axes.
• The dilepton angular distribution continues to be characterized by a frame-independent identity also when the Lam-Tung relation is violated.