Abstract
Abstract The discovery of Kaluza-Klein (KK) gravitons is a smoking gun of extra dimensions. Other scenarios, however, could give rise to spin-two resonances of a new stronglycoupled sector and act as impostors. In this paper we prove that a spin-two resonance does not couple to the Standard Model through dimension-four operators. We then show that the massive graviton and its impostor both couple to the Standard Model through the same dimension-five operators. Therefore the spin determination is identical. Nevertheless, we also show that one can use the ratio of branching ratios to photons and to jets for distinguishing between KK gravitons and their impostors. The capacity to distinguish between KK gravitons and impostors is a manifestation of the breakdown of the duality between AdS and strongly-coupled theories.
Highlights
JHEP12(2012)062 graviton G and the impostor Gwould both be massive spin-two resonances
In this paper we prove that a spin-two resonance does not couple to the Standard Model through dimension-four operators
We show that the massive graviton and its impostor both couple to the Standard Model through the same dimension-five operators
Summary
We show that the KK graviton G and the spin-two meson from new strong interactions Ghave the same propagation, described by the Fierz-Pauli Lagrangian for massive spin-two resonances [7]. In the Fierz-Pauli Lagrangian, a spin-two field is described by a rank-two symmetric and traceless tensor, Gμν = Gνμ , Gμμ = 0. Note that the metric is conformally flat, which allows the following separation. Where GflMatN is the Einstein tensor in Minkowski space-time, and it contains the Fierz-Pauli equation for the graviton in flat space-time. Because the warp factor is only a function of the extra dimension coordinate z, only derivatives with respect to z will appear in δGMN. Upon KK decomposition of the graviton field, Gμν(x, z) = n Gnμν(x)χn(z), terms in δGMN appear in the differential equation for the 5D wavefunction χn(z) of excited KK gravitons [8, 9], while the kinetic term in four dimensions remains the same as the flat space-time case, i.e. the Fierz-Pauli equation. All KK excitations behave as 4D Fierz-Pauli fields, and the same equations as eqs. (2.1) and (2.2) apply to G.2 note that we could generalize this argument to D > 5
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