Heavy-Particle Spacetime Symmetries and Building Blocks

Abstract

What is heavy particle effective theory? Imagine a charged particle ϕ with mass M in its rest frame, interacting with other particles of energy \(\Lambda \ll M\) through exchange of photons. The momentum transfer in such collisions are of order \(\Lambda \), allowing the heavy particle to be off-shell by only that amount. Hence, to a good approximation, the heavy particle remains at rest and appears to the light degrees of freedom as a static source of charge.