Available Decay Model
2-body decays
1. "gls-bf", "default"
(HelicityDecay
)
default decay model
The total amplitude is
\[A = H_{\lambda_{B},\lambda_{C}}^{A \rightarrow B+C} D^{J_A*}_{\lambda_{A}, \lambda_{B}-\lambda_{C}} (\varphi,\theta,0)\]The helicity coupling is
\[H_{\lambda_{B},\lambda_{C}}^{A \rightarrow B+C} = \sum_{ls} g_{ls} \sqrt{\frac{2l+1}{2 J_{A}+1}} \langle l 0; s \delta|J_{A} \delta\rangle \langle J_{B} \lambda_{B} ;J_{C} -\lambda_{C} | s \delta \rangle q^{l} B_{l}'(q, q_0, d)\]The fit parameters is \(g_{ls}\)
There are some options
(1).
has_bprime=False
will remove the \(B_{l}'(q, q_0, d)\) part.(2).
has_barrier_factor=False
will remove the \(q^{l} B_{l}'(q, q_0, d)\) part.(3).
barrier_factor_norm=True
will replace \(q^l\) with \((q/q_{0})^l\)(4).
below_threshold=True
will replace the mass used to calculate \(q_0\) with\[m_0^{eff} = m^{min} + \frac{m^{max} - m^{min}}{2}(1+tanh \frac{m_0 - \frac{m^{max} + m^{min}}{2}}{m^{max} - m^{min}})\](5).
l_list=[l1, l2]
andls_list=[[l1, s1], [l2, s2]]
options give the list of all possible LS used in the decay.(6).
no_q0=True
will set the \(q_0=1\).
2. "helicity_full"
(HelicityDecayNP
)
Full helicity amplitude
\[A = H_{m_1, m_2} D_{m_0, m_1-m_2}^{J_0 *}(\varphi, \theta,0)\]fit parameters is \(H_{m_1, m_2}\).
3. "helicity_parity"
(HelicityDecayP
)
\[H_{- m1, - m2} = P_0 P_1 P_2 (-1)^{J_1 + J_2 - J_0} H_{m1, m2}\]
4. "gls-cpv"
(HelicityDecayCPV
)
decay model for CPV
5. "gls_reduce_h0"
(HelicityDecayReduceH0
)
decay model that remove helicity =0 for massless particles