LHC signals for KK graviton from an extended warped extra dimension

Abstract

We analyze signals at the Large Hadron Collider (LHC) from production and decay of Kaluza-Klein (KK) gravitons in the context of “extended” warped extra-dimensional models, where the standard model (SM) Higgs and fermion fields are restricted to be in-between the usual ultraviolet/Planck brane and a ∼ O(10) TeV (new, “intermediate”) brane, whereas the SM gauge fields (and gravity) propagate further down to the ∼ O(TeV) infrared brane. Such a framework suppresses flavor violation stemming from KK particle effects, while keeping the KK gauge bosons and gravitons accessible to the LHC. We find that the signals from KK graviton are significantly different than in the standard warped model. This is because the usually dominant decay modes of KK gravitons into top quark, Higgs and longitudinal W/Z particles are suppressed by the above spatial separation between these two sets of particles, thus other decay channels are allowed to shine themselves. In particular, we focus on two novel decay channels of the KK graviton. The first one is the decay into a pair of radions, each of which decays (dominantly) into a pair of SM gluons, resulting in a resonant 4-jet final state consisting of two pairs of dijet resonance. On the other hand, if the radion is heavier and/or KK gluon is lighter, then the KK graviton mostly decays into a KK gluon and a SM gluon. The resulting KK gluon has a significant decay branching fraction into radion and SM gluon, thereby generating (again) a 4-jet signature, but with a different underlying event topology, i.e., featuring now three different resonances. We demonstrate that the High-Luminosity LHC (HL-LHC) has sensitivity to KK graviton of (up to) ∼ 4 TeV in both channels, in the specific model with only gluon field (and gravity) propagating in the extended bulk, whereas it is unlikely to have sensitivity in the standard dijet resonance search channel from KK graviton decay into two gluons.

Signals of $W'$ and $Z'$ bosons at the LHC in the $SU(3) \times SO(5) \times U(1)$ gauge-Higgs unification

“…Collider physics of radions, KK gravitons and KK gluons are also important subjects in models defined on a higher dimensional spacetime [76,77]. For instance, KK gluons mediate dijet and t t production processes at hadron colliders.…”

Conformal freeze-in, composite dark photon, and asymmetric reheating

“…, have profiles localized to the intermediate brane at z = z 1 , they have sizable coupling with the dark U(1) D gauge boson A (1) D . 23 If T R ∼ Λ 1 (but less than confinement phase transition temperature), these KK modes can be excited and can easily populate the dark sector. If T R Λ 1 , they are not produced cosmologically; leaving only the zero mode, B (0) µ , (i.e.…”

Snowmass2021 White Paper: Collider Physics Opportunities of Extended Warped Extra-Dimensional Models

“…An interesting signature is the four-jet final state stemming from the processes, G KK → ϕϕ, ϕ → gg (called "radion channel") and G KK → gg KK , g KK → gϕ, ϕ → gg (called "KK gluon channel"), with G KK and g KK denoting the lightest KK graviton mode and the lightest KK gluon mode, respectively (see Figure 7). These channels become more significant especially in the model variation where the SM gluon field is propagating in the extended bulk while the propagation of EW fields is restricted to the Higgs brane [17] (see Figure 8), in part because radion decays to di-photon (golden channel) are then extremely suppressed. Depending on the underlying mass spectrum, one channel is leading to the other, and different search strategies are motivated due to the difference of the associated event topologies.…”

“…Depending on the underlying mass spectrum, one channel is leading to the other, and different search strategies are motivated due to the difference of the associated event topologies. We have performed a sensitivity study with a few well-motivated benchmark sets of parameter values giving well-separated four jets, and found that the HL-LHC (3,000 fb −1 ) would be sensitive to the KK graviton signals by ∼ 2.5 − 5σ significance [17]. It was further found that the radion channel can be the first discovery channel of KK graviton due to the effectiveness of the cuts designed for the event topology of the radion channel signal, while the KK gluon channel can serve as a cross-check to understand the structure of the underlying model.…”

“…Only EW in the extended bulk [13,14] (III). Only QCD in the extended bulk [17] Heavy radion ( 1 TeV) isolated three bosons mixture of gluons and W/Z/γ (Fig. 2) mixture of W/Z/γ (Fig.…”