What is included in composite particles ?
In theoretical physics , the Weinberg – Witten theorem ( WW ) , proved by Steven Weinberg and Edward Witten , states that massless particles ( either composite or elementary ) with spin " j " > 1/2 can not carry a Lorentz - covariant current , while massless particles with spin " j " > 1 can not carry a Lorentz - covariant stress - energy .