Using Scalars to Probe Theories of Low Scale Quantum Gravity

TL;DR

This paper explores how scalar pair production at various colliders can serve as a probe for low-scale quantum gravity theories involving extra dimensions, focusing on graviton tower exchange effects.

Contribution

It introduces a novel method using scalar pair production processes to test theories of low-scale quantum gravity with extra dimensions at colliders.

Findings

Potentially large cross sections at LHC and future colliders

Polarization enhances sensitivity in gamma-gamma collisions

Tree-level scalar pair production can reveal graviton effects

Abstract

Arkani-Hamed, Dimopoulos and Dvali have recently suggested that gravity may become strong at energies near 1 TeV which would remove the hierarchy problem. Such a scenario can be tested at present and future colliders since the exchange of towers of Kaluza-Klein gravitons leads to a set of new dimension-8 operators that can play important phenomenological roles. In this paper we examine how the production of pairs of scalars at $e^+e^-$, $\gamma \gamma$ and hadron colliders can be used to further probe the effects of graviton tower exchange. In particular we examine the tree-level production of pairs of identical Higgs fields which occurs only at the loop level in both the Standard Model and its extension to the Minimal Supersymmetric Standard Model. Cross sections for such processes are found to be potentially large at the LHC and the next generation of linear colliders. For the $\gamma\gamma$ case the role of polarization in improving sensitivity to graviton exchange is emphasized.