Unparticle physics with broken scale invariance

TL;DR

This paper explores the possibility of detecting unparticles with broken scale invariance at colliders, especially around the Z boson mass, by analyzing constraints from collider data and astrophysics.

Contribution

It demonstrates that vector unparticles can naturally have a scale mu in the 1 GeV to M_Z range, enabling collider probes, and provides updated constraints from experimental data.

Findings

Unparticles with broken scale invariance can be probed at colliders.

Constraints on unparticle parameters are derived from collider data.

Vector unparticles can have a scale mu between 1 GeV and M_Z.

Abstract

If scale invariance is exact, unparticles are unlikely to be probed in colliders since there are stringent constraints from astrophysics and cosmology. However these constraints are inapplicable if scale invariance is broken at a scale mu >~ 1 GeV. The case 1 GeV <~ mu < M_Z is particularly interesting since it allows unparticles to be probed at and below the Z pole. We show that mu can naturally be in this range if only vector unparticles exist, and briefly remark on implications for Higgs phenomenology. We then obtain constraints on unparticle parameters from e+ e- -> mu+ mu- cross-section and forward-backward asymmetry data, and compare with the constraints from mono-photon production and the Z hadronic width.