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

TL;DR

This paper investigates small-x effects in the production of Kaluza-Klein gravitons and radions at the LHC, highlighting how these effects influence angular distributions of decay products within extra-dimensional models.

Contribution

It introduces a method to include small-x effects in graviton and radion production calculations using the $k_T$-factorization approach with CCFM-evolved unintegrated parton densities.

Findings

Small-x effects alter angular distributions of decay products.

The approach demonstrates potential observable differences at LHC energies.

Provides a framework for incorporating small-x corrections in extra-dimensional models.

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 Ciafaloni-Catani-Fiorani-Marchesini (CCFM) evolution equation, which resums the leading logarithmic small-$x$ corrections to the production cross sections. We demonstrate that the small-$x$ effects can manifest themselves in the different angular distributions of graviton decay products and give some examples of how these distributions can look like at the LHC energies.