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

We investigate contributions of Kaluza-Klein (KK) graviton in extra dimension models to the process pp -> p gamma p -> p gamma 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 gamma q initial state as in the Compton scattering in the standard model, the gamma 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 cutoff scale for the ADD model is 6.3 TeVat 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/(M) over bar (Pl) = 0.1(0.01) for the RS model.