Dark Radiation Confronting LHC in Z' Models

TL;DR

This paper examines how TeV-scale Z' models, which predict light right-handed neutrinos as dark radiation, align with cosmological evidence and collider constraints from the LHC.

Contribution

It provides an analysis of E6 Z' models' parameter space to reconcile dark radiation observations with existing LHC bounds.

Findings

Certain Z' model parameters can explain dark radiation without conflicting with LHC data.

Constraints from LHC searches significantly restrict the viable parameter space for these models.

The study highlights the importance of collider data in testing cosmological dark radiation scenarios.

Abstract

Recent cosmological data favour additional relativistic degrees of freedom beyond the three active neutrinos and photons, often referred to as "dark radiation". Extensions of the SM involving TeV-scale Z' gauge bosons generically contain superweakly interacting light right-handed neutrinos which can constitute this dark radiation. In this letter we confront the requirement on the parameters of the E6 Z' models to account for the present evidence of dark radiation with the already existing constraints from searches for new neutral gauge bosons at LHC7.