Implications of diphoton searches for a radion in the bulk-Higgs scenario

Abstract

In this work we point out that the apparent diphoton excess initially presented by the ATLAS and CMS collaborations could have originated from a radion in the bulk Higgs scenario within a warped extra dimension. In this scenario the couplings of the radion to massive gauge bosons are suppressed, allowing it to evade existing searches. In the presence of mixing with the Higgs, due to the strong constraints from diboson searches, only points near what we denominate the alignment region were able to explain the diphoton signal and evade other experimental constraints. In light of the new measurements presented at ICHEP 2016 by both LHC collaborations, which do not confirm the initial diphoton excess, we study the current and future collider constraints on a radion within the bulk-Higgs scenario. We find that searches in the diphoton channel provide the most powerful probe of this scenario and already exclude large regions of parameter space, particularly for smaller warp factors. The radion has a sizeable branching ratio into top pairs and this channel may also give competitive constraints in the future. Finally, diHiggs searches can provide a complementary probe in the case of non-zero radion-Higgs mixing but strong alignment.

On dilatons and the LHC diphoton excess

“…In ref. [55] they succeed to explain the diphoton excess but giving up to explain the UV/IR full hierarchy, while in our work we insist in solving the gauge hierarchy as an initial requirement. In ref.…”

“…While completing this manuscript some references [53][54][55][56] where posted on arXiv where the possibility of a 750 GeV radion to explain the LHC diphoton excess was studied. In particular the results from ref.…”

Implications of the absence of high-mass radion signals

“…[3][4][5] and [6], the latter showing the dominance of the φ → γγ, gg decay modes near the conformal limit in the case of m φ = 500 GeV. Aside from the earlier version of this paper, the radion/dilaton interpretation of the observed 750 GeV di-photon excess was also discussed in [7][8][9][10][11].…”

Precision tools and models to narrow in on the 750 GeV diphoton resonance

“…This possibility would be favoured by a large width of the resonance, as first indications seem to suggest. Another possibility is to interpret the signal in the context of extra-dimensional models [5,9,29,30,48,84,125,141,203,225,312], with the resonance being a scalar, a graviton, a dilaton, or a radion, depending on the scenario. However, some of these interpretations are in tension with the non-observation of this resonance in other channels.…”