Jet observables and energy-momentum tensor

We clarify and extend the theorem of Sveshnikov and Tkachov [hep-ph/9512370], which gives an explicit connection between jet observables and energy-momentum tensor. We check the relation between jet observables and energy-momentum tensor for non-scalar (spinor and vector) field, give a correct treatment of the light-cone singularity for massless particles, and extend the theorem to the massless case. We also discuss the issue of gauge invariance.