Abstract
Light radions constitute one of the few surviving possibilities for observable new particle states at the sub-TeV level which arise in models with extra spacetime dimensions. It is already known that the 125 GeV state discovered at CERN is unlikely to be a pure radion state, since its decays resemble those of the Standard Model Higgs boson too closely. However, due to experimental errors in the measured decay widths, the possibility still remains that it could be a mixture of the radion with one (or more) Higgs states. We use the existing LHC data at 8 and 13 TeV to make a thorough investigation of this possibility. Not surprisingly, it turns out that this model is already constrained quite effectively by direct LHC searches for an additional scalar heavier than 125 GeV. We then make a detailed study of the so-called ‘conformal point’, where this heavy state practically decouples from (most of) the Standard Model fields. Some projections for the future are also included.
Highlights
The 2012 discovery [1], at the LHC, of a weakly-interacting light scalar state—which appears from all current indications to be an elementary Higgs particle—revives the old question of how the mass of such a scalar can remain stable against large electroweak corrections in a theory with a momentum cutoff at some very high scale
Though there are strong constraints on such a light radion per se, there remains room for a light radion mixed with the Standard Model (SM) Higgs boson to survive
We have explored this possibility, using an existing formalism, in the light of current data from the LHC Runs 1 and 2
Summary
The 2012 discovery [1], at the LHC, of a weakly-interacting light scalar state—which appears from all current indications to be an elementary Higgs particle—revives the old question of how the mass of such a scalar can remain stable against large electroweak corrections in a theory with a momentum cutoff at some very high scale. Goldberger and Wise augmented the model by the introduction of a bulk scalar B(x, y), with a mass MB and quartic self-interactions on the IR and UV branes, with vacuum expectation values VIR and VUV respectively—all these mass-dimension quantities being in the ballpark of the Planck mass. They were able to show that the scalar modulus field T (x) develops a potential with a minimum at
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