Dilaton constraints and LHC prospects

TL;DR

This paper explores constraints on a dilaton particle arising from electroweak symmetry breaking via conformal dynamics, using LHC and LEP data to set bounds on its mass and the conformal breaking scale, and discusses prospects for detecting it.

Contribution

It provides the first detailed analysis translating Higgs search limits into constraints on a dilaton in a conformal symmetry breaking scenario, including LHC prospects.

Findings

Conformal breaking scale f > 1 TeV for dilaton masses 145-600 GeV.

Dilaton production rate can be up to 10 times the SM Higgs in certain channels.

Dilaton with mass below 110 GeV can be narrow and detectable in gamma gamma channel.

Abstract

The Standard Model Higgs searches using the first 1-2 fb-1 of LHC data can be used to put interesting constraints on new scalar particles other than the Higgs. We investigate one such scenario in which electroweak symmetry is broken via strongly coupled conformal dynamics. This scenario contains a neutral scalar dilaton---the Goldstone boson associated with spontaneously broken scale invariance---with a mass below the conformal symmetry breaking scale and couplings to Standard Model particles similar (but not identical) to those of the Standard Model Higgs boson. We translate the LEP and LHC Higgs limits to constrain the dilaton mass and conformal breaking scale. The conformal breaking scale f is constrained to be above 1 TeV for dilaton masses between 145 and 600 GeV, though it can be as low as 400 GeV for dilaton masses below 110 GeV. We also show that (i) a dilaton chi with mass below 110 GeV and consistent with the LEP constraints can appear in gg --> chi --> gamma gamma with a rate up to ~10 times the corresponding Standard Model Higgs rate, and (ii) a dilaton with mass of several hundred GeV is much narrower than the corresponding Standard Model Higgs, leading to improved search sensitivity in chi --> ZZ --> 4l.