Graviton Signals in Central Production at the LHC

Abstract

We study central production, in the inclusive case, to look for graviton signals in a large extra dimensional model using dilepton and diphoton channels. We carefully analyze signal and possible standard model background processes and study the feasibility of such new physics searches in a relatively clean environment as in central production where the proton fragments are mostly emitted in the forward direction, and there is a clear rapidity gap between them and the centrally produced system. Our analysis shows that the LHC with 14 TeV center of mass energy and 100 fb −1 (300 fb −1 ) of integrated luminosity can probe the effective gravity scale up to 3.6 TeV (4.4 TeV) in both the dilepton and diphoton channels.

Possible small- x effects in the Kaluza-Klein graviton and radion production at high energies

“…where k sums over all KK towers below M s scale. As it was already mentioned above, in the ADD model the mass separation between two adjacent KK modes is a O(1/R), so that KK modes become quasicontinuous and the summation in ( 24) can be done by defining KK state density [38,39]. For n number of extra dimensions, the P eff is given by…”

“…This summation compensates the suppression of each KK mode coupling to the SM particles by Planck mass and gives rise to a substantial effective coupling strength. Following [38,39], we have to replace the graviton propagator by the effective one:…”

“…Another example is the distributions in the scattering angle θ * of KK decay leptons or photons in the KK graviton center-of-mass frame. At LO, the on-shell gluon-gluon fusion processes, which dominate at the LHC energies, behave as 1−cos 4 θ * and 1+6 cos 2 θ * +cos 4 θ * for dilepton and diphoton decay modes, respectively (see, for example, [38,39]). In the k Tfactorization approach, taking into account the initial gluon off-shellness can result to the deviations from these simple forms, as it is demonstrated in Figs.…”