Definitions

# Available energy (particle collision)

In particle physics, the available energy is the energy in a particle collision available to produce new matter from the kinetic energy of the colliding particles. Since the conservation of momentum must be held, a system of two particles with a net momentum may not convert all their kinetic energy into mass - and thus the available energy is always less than or equal to the kinetic energy of the colliding particles. The available energy for a system of one stationary particle and one moving particle is defined as:
$E_a = sqrt\left\{2 m_t c^2 E_m + \left(m_t c^2\right)^2 + \left(m_k c^2\right)^2\right\}$
where
$m_t$ is the mass of the stationary target particle,
$m_k$ is the mass of the moving particle,
$E_m$ is the kinetic energy of the moving particle, and
$c$ is the speed of light.