In particle physics, the mathematical combination of a particle's energy and its momentum to give a value for the mass of the particle at rest. The invariant mass is the same for all frames of reference (see Special Relativity).
The invariant mass of a system of decay particles is related to the rest mass of the original particle by the following equation:
W2c4=(ΣE)2-(Σpc)2
where:
- W is the invariant mass of the system of particles
- ΣE is the sum of the energies of the particles
- Σp is the vector sum of the momenta of the particles (includes both magnitude and direction of the momenta)
- c is the speed of light