Bounds from LEP on unparticle interactions with electroweak bosons

TL;DR

This paper uses LEP data to set bounds on unparticle interactions with electroweak bosons, constraining potential signals at the LHC and advancing understanding of hidden conformal sectors.

Contribution

It provides new bounds on unparticle-electroweak interactions from LEP data and improves limits on four-photon production via unparticle self-interactions.

Findings

Maximum cross-section for four-photon production is a few tens of femtobarns at 14 TeV LHC.

Bounds on unparticle interactions are significantly improved using LEP data.

Predicted signals are well below 1 fb for a wide parameter range.

Abstract

A conformally invariant hidden sector is considered, with a scalar operator $O$ of low dimension that couples to the electro-weak gauge bosons of the Standard Model, via terms such as $O F^{\mu\nu}F_{\mu\nu}$. By examining single photon production at LEP, we bound the strength of these interactions. We apply our results, along with those of Delgado and Strassler and of Caracciolo and Rychkov, to improve the bound on four-photon production through "unparticle self-interactions", as proposed by Feng et al. We find the maximum allowable cross-section is of order a few tens of femtobarns at the 14 TeV LHC, and lies well below 1 fb for a wide range of parameters.