Search for Kaluza-Klein gravitons in extra dimension models via forward detectors at the LHC

Abstract

We investigate contributions of Kaluza-Klein (KK) graviton in extra dimension models to the process $pp\to p{\hat{I}}^{3}p\to p{\hat{I}}^{3}jX$, where a proton emits a quasireal photon and is detected by using the very forward detectors planned at the LHC. In addition to the ${\hat{I}}^{3}q$ initial state as in the Compton scattering in the standard model, the ${\hat{I}}^{3}g$ scattering contributes through the $t$-channel exchange of KK gravitons. Taking account of pileup contributions to the background and examining viable kinematical cuts, constraints on the parameter space of both the ADD (Arkani-Hamed, Dimopoulos and Dvali) model and the RS (Randall and Sundrum) model are studied. With 200 fb${}^{-1}$ data at a center-of-mass energy of 14 TeV, the expected lower bound on the cut-off scale for the ADD model is 6.3 TeV at 95% confidence level, while a lower limit of 2.0 (0.5) TeV is set on the mass of the first excited graviton with the coupling parameter $k/{\overline{M}}_{\mathrm{Pl}}=0.1$ (0.01) for the RS model.

16 pages, 11 figures, 1 table; v2: a footnote and references added, version to appear in PRD