Function breakup_momentum 

pub fn breakup_momentum(m0: Float, m1: Float, m2: Float) -> Float

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

Note that this version will always yield a real-valued number.