Abstract
In theories with a warped extra dimension, composite fermions, as e.g. the right-handed top quark, can be very strongly coupled to Kaluza-Klein (KK) fields. In particular, the KK gluons in the presence of such composite fields become very broad resonances, thus remarkably modifying their experimental signatures. We have computed the pole mass and the pole width of the KK gluon, triggered by its interaction with quarks, as well as the prediction for proton-proton cross-sections using the full propagator and compared it with that obtained from the usual Breit-Wigner approximation. We compare both approaches, along with the existing experimental data from ATLAS and CMS, for the toverline{t} , toverline{t}W , toverline{t}Z , toverline{t}H , and ttoverline{tt} channels. We have found differences between the two approaches of up to about 100%, highlighting that the effect of broad resonances can be dramatic on present, and mainly future, experimental searches. The channel ttoverline{tt} is particularly promising because the size of the cross-section signal is of the same order of magnitude as the Standard Model prediction, and future experimental analyses in this channel, especially for broad resonances, can shed light on the nature of possible physics beyond the Standard Model.
Highlights
Mass cannot be reconstructed, present experimental searches on KK-gluon production focus on searching for bumps on the invariant mass of its decay products, e.g. in G → qq
We will concentrate in the production of the first KK mode (G ≡ G(1)) of gluons, as they are the most strongly coupled and model independent extra particles in the theory, and consider the effect of broad resonances by computing the pole masses and pole decay widths as the zeros of the inverse renormalized propagator; as it will be shown, this effect cannot be neglected for strongly coupled fields and broad resonances
In theories with a warped extra dimension and two branes, i.e. the UV and the IR, the Higgs field must be localized toward the IR brane in order to solve the hierarchy problem
Summary
SU(2)L ⊗ U(1)Y , which is just the SM gauge group In this class of models, we can understand the improvement from the electroweak constraints by the fact that the physical Higgs boson profile, h(y) = h(0)eαky−A(y) with α > 2 to solve the hierarchy problem, unlike the case of the RS metric, is peaked away from the IR brane [40], while the KK modes are localized toward the IR brane, which makes their overlap small enough to cope with electroweak constraints for a choice of the model parameters. As the coupling of G with two gluons vanishes, by orthonormality of the wave functions, quarks are the only decay channels that we will consider in this work
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