cg

This module provides the function cg_coef() to calculate the Clebsch-Gordan coefficients \(\langle j_1m_1j_2m_2|JM\rangle\).

This function has interface to SymPy functions if it’s installed correctly. Otherwise, it will depend on the input file tf_pwa/cg_table.json.

cg_coef(jb, jc, mb, mc, ja, ma)

It returns the CG coefficient \(\langle j_bm_bj_cm_c|j_am_a\rangle\), as in a decay from particle a to b and c. It will either call sympy.physics.quantum.cg() or get_cg_coef().

get_cg_coef(j1, j2, m1, m2, j, m)

If SymPy is not installed, [deprecation] cg_coef() will call this function and derive the CG coefficient by searching into tf_pwa/cg_table.json.

In fact, tf_pwa/cg_table.json only stores some of the coefficients, the others will be obtained by this function using some symmetry properties of the CG table.

Note

tf_pwa/cg_table.json only contains the cases where \(j_1,j_2\leqslant4\), but this should be enough for most cases in PWA.