Function complex_breakup_momentum 

pub fn complex_breakup_momentum(m0: f64, m1: f64, m2: f64) -> Complex64

Computes the breakup momentum (often denoted $q$) for a particle with mass $m_0$ decaying into two particles with masses $m_1$ and $m_2$: $\frac{m_0 \rho(m_0^2, m_1, m_2)}{2}$.