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

Abstract

We study the single graviton production at the CERN LHC using the ${k}_{T}$-factorization approach of QCD. We consider the Arkani-Hamed-Dimopoulos-Dvali scenario and Randall-Sundrum model with one warped extra dimension and derive the production amplitudes for spin-2 (Kaluza-Klein excitation of the graviton) and spin-0 (radion) states, including subsequent graviton decay into the dilepton or diphoton pairs. We use the transverse momentum dependent (unintegrated) parton densities in a proton obtained from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation, which resums the leading logarithmic small-$x$ corrections to the production cross sections, and estimate the uncertainties of our predictions. We demonstrate that the small-$x$ effects can manifest themselves in the different angular distributions of graviton decay products and give some examples of what these distributions can look like at the LHC energies.