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Revisiting the Real Graviton Effects at CERN LHC within the Quantum Gravity Theory with Large Extra Dimensions

CERN LHC provides a good experimental platform to perturbatively probe the fundamental gravity scale up to several TeV, with the precise value depending on the number of extra dimensions. The leading experimental signal of graviton at LHC is from the process $pp\to jet+{E\slash}_T$, where ${E\slash}_T$ stands for the transverse missing energy. A detailed discussion on the hadronic production of real graviton through hard subprocesses: $q\bar{q}\to G+g$, $g+q\to G+q$ and $g+g\to G+g$ have been studied within the quantum gravity theory with large extra dimensions. The main theoretical uncertainties together with the dominant standard model background to these processes, e.g. $q\bar{q}\to Z^0+g$ and $g+q\to Z^0+q$ with $Z^0$ further decaying into neutrinos, have also been discussed. It is found that only in certain jet energy region and with certain number of extra dimensions can the quantum gravity signal be distinguished from the background, which inversely lead to the effective scale $M_D$ to be probed up to $(8.8\pm 0.9)$ TeV for two extra dimensions, and $(5.9\pm 0.5)$ TeV for four extra dimensions with sufficient integrated luminosity, e.g. $100fb^{-1}$, at CERN LHC.