A light dilaton at the LHC

Abstract

In this paper, we explore the possibility that a light dilaton can be the first sign of new physics at the LHC. The dilaton could emerge in approximate scale invariant UV completions of the SM as the Goldstone boson associated with the spontaneous breaking of the scale invariance. We study in detail the phenomenology of the dilaton at the LHC in the mass range of [10−300] GeV including the case where the dilaton can mix with the SM Higgs boson, leading to an interesting interplay between direct and indirect constraints. A possibility that the dilaton act as a portal to a dark sector is also considered. As a minimal realization, the dark sector includes a dark photon lighter than the dilaton implying sizeable missing energy signatures. Several simplified benchmark models that can encode different UV completions are discussed, for which we scrutinize the current and future LHC reach.

Heavy dark matter through the dilaton portal

“…Any theory can be made scale invariant by coupling it to a dilaton. The scale invariance can then be softly broken, giving the dilaton a mass and self-interactions, and this becomes a popular proposal [1][2][3][4][5][6][7][8][9][10][11][12][13][14] for solving the hierarchy problem of the Standard Model (SM). Such SM plus dilaton theories can either be thought of as fundamental, or as the low-energy limit of composite theories, where the dilaton becomes the pseudo-Goldstone boson associated with the spontaneous breaking of scale invariance.…”

“…In particular, we shall restrict our attention to a heavy dilaton above about 300 GeV (see ref. [14] for a detailed recent examination of constraints on the dilaton in the low-mass window) where diboson searches push the dilaton to large masses and weak couplings. However, a vector dark matter candidate is produced much more copiously at the LHC than a fermion candidate, and thus this model is more promising for future searches.…”