Graviton phenomenology of linear dilaton geometries

Abstract

Five-dimensional geometries with a linearly varying dilaton background arise as gravity duals of TeV Little String Theories (LSTs) and provide a solution of the hierarchy problem through extra dimensions. The unique Kaluza-Klein graviton spectrum has a mass gap on the order of the dilaton slope followed by a closely spaced discretum of states. We study in detail the graviton phenomenology in this scenario, allowing the dilaton slope to vary from the MeV to the TeV scale. When the dilaton slope is large enough so that individual KK resonances can be resolved at the LHC, several of them can be discovered simultaneously and allow for the linear dilaton geometry to be uniquely identified. For much smaller values of the dilaton slope, the LHC signatures become similar to the 5-d ADD scenario while relaxing the astrophysical and experimental constraints. Due to the mass gap, the KK modes are produced on-shell and decay inside the LHC detector, modifying the diphoton and dilepton spectra at large invariant mass. Finally, we perform a similar analysis for the low curvature RS geometry. We present experimental limits and calculate the ultimate reach of a 14 TeV LHC for all the above scenarios.