The coupling of an unparticle operator OU to standard model particles opens up the possibility of unparticle decays into standard model fields. We study this issue by analyzing the pole structure (and spectral function) of the unparticle propagator, corrected to account for one-loop polarization effects from virtual standard model particles. We find that the propagator of a scalar unparticle (of scaling dimension 1≤dU<2) with a mass gap mg develops an isolated pole, mp2-imp∏p, with mp2 mg2 below the unparticle continuum that extends above mg (showing that the theory would be unstable without a mass gap). If that pole lies below the threshold for decay into two standard model particles, it corresponds to a stable unparticle state (and its width∏p is zero). For mp2 above the threshold, the width is nonzero and related to the rate of the unparticle decay into standard model particles. This picture is valid for any value of dU in the considered range. © 2009 The American Physical Society.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 2 Mar 2009|