# Neutron mass [MeV/c²]
const mₙ = 939.565
# Proton mass [MeV/c²]
const mₚ = 939.272
# Reduced np mass [MeV/c²]
const m_np= 2*(mₙ*mₚ)/(mₙ+mₚ) /197
const m_pn = m_np
# Pion± mass [MeV/c²]
const m_πpm = 139.570
# Pion0 mass [MeV/c²]
const m_π0 = 134.977
const m_π = (2m_πpm + m_π0)/3
