Effects of Unparticles on Running of Gauge Couplings

TL;DR

This paper investigates how unparticles, hypothetical entities with non-integer scaling dimensions, influence the running of gauge couplings, potentially altering asymptotic freedom and unification patterns in the Standard Model.

Contribution

It provides a novel calculation of unparticle contributions to the gauge coupling beta function, revealing their potential to modify asymptotic freedom and gauge coupling unification.

Findings

Unparticles with d>2 can accelerate asymptotic freedom in non-Abelian theories.

Unparticles can lead to gauge coupling unification at intermediate scales.

High unparticle scales might still be accessible at colliders like LHC and ILC.

Abstract

Unparticles charged under a gauge group can contribute to the running of the gauge coupling. We show that a scalar unparticle of scaling dimension d contributes to the \beta function a term that is (2-d) times that from a scalar particle in the same representation. This result has important implications on asymptotic freedom. An unparticle with d>2, in contrast to its matter counterpart, can speed up the approach to asymptotic freedom for a non-Abelian gauge theory and has the tendency to make an Abelian theory also asymptotically free. For not spoiling the excellent agreement of the standard model (SM) with precision tests, the infrared cut-off, m, of such an unparticle would be high but might still be reachable at colliders such as LHC and ILC. Furthermore, if the unparticle scale \Lambda_\calU is high enough, unparticles could significantly modify the unification pattern of the SM gauge couplings. For instance, with 3 scalar unparticles of d\sim 2.5 in the adjoint representation of the strong gauge group but neutral under the electroweak one, the three gauge couplings would unify at a scale of \sim 8\times 10^{12} {\rm GeV}, which is several orders of magnitude below the supersymmetric unification scale.