Helicity formalism

Warning

These pages are under development.

Todo

• Lorentz-invariance of helicity operator

• Types

  • Two-body decay amplitude

  • Sequential two-body decay amplitude

• Definition of angles

  • Production angle

  • Helicity angle

  • Treiman-Yang angle

  • Overview of kinematic variables

• Dynamics:

  • Wigner-D functions

  • Clebsch-Gordan coefficients

• Kinematic variables

• An example

Canonical formulation

Alignment problem

Recommended literature:

• General introductions to helicity angles:
  [Kutschke, 1996, Richman, 1984]

• Suggested solutions:
  [Chen and Ping, 2017, Marangotto, 2020, Wang et al., 2020, Mikhasenko et al., 2020]

• LHCb study that led to these solution papers:
  [Aaij et al., 2015]