These results will be applied to both massive and massless particles.
A typical example is offered by a free massive particle and, in this case, the constant has the value 1/m.
The photon in this model becomes a massive particle at low temperatures.
The existence of massive superluminal particles is a controversial issue.
The spectrum of the model consists of a single massive particle.
These massive particles are also seen to decay into 2-3 particles.
Because electrons are so much smaller than atoms, there must be other, more massive particles in the atom.
Rather counterintuitively, more massive particles are, in general, more difficult to produce.
Quarks are massive particles, and therefore are also subject to gravity.
In particular, massive particles can interfere and therefore diffract.