helicity¶

import ampform.helicity

Generate an amplitude model with the helicity formalism.

class CanonicalAmplitudeBuilder(reaction_result: qrules.transition.Result)[source]¶

Bases: ampform.helicity.HelicityAmplitudeBuilder

Amplitude model generator for the canonical helicity formalism.

This class defines a full amplitude in the canonical formalism, using the helicity formalism as a foundation. The key here is that we take the full helicity intensity as a template, and just exchange the helicity amplitudes \(F\) as a sum of canonical amplitudes \(A\):

\[F^J_{\lambda_1,\lambda_2} = \sum_{LS} \mathrm{norm}(A^J_{LS})C^2.\]

Here, \(C\) stands for Clebsch-Gordan factor.

class HelicityAmplitudeBuilder(reaction_result: qrules.transition.Result)[source]¶

Bases: object

Amplitude model generator for the helicity formalism.

generate() → ampform.helicity.HelicityModel [source]¶

set_dynamics(particle_name: str, dynamics_builder: ampform.dynamics.builder.ResonanceDynamicsBuilder) → None [source]¶

class HelicityModel(expression: sympy.core.expr.Expr, parameter_defaults: Dict[sympy.core.symbol.Symbol, Union[float, complex, int]], components: Dict[str, sympy.core.expr.Expr], adapter: ampform.kinematics.HelicityAdapter, particles: qrules.particle.ParticleCollection)[source]¶

Bases: object

__eq__(other)¶: Method generated by attrs for class HelicityModel.

property adapter¶

property components¶

property expression¶

property parameter_defaults¶

particles: qrules.particle.ParticleCollection¶

class State(particle: qrules.particle.Particle, spin_projection)[source]¶

Bases: object

__eq__(other)¶: Method generated by attrs for class State.

particle: qrules.particle.Particle¶

spin_projection: float¶

AmpForm

helicity¶