Searching for anomalous top quark interactions with proton tagging and timing detectors at the LHC

We study the LHC sensitivity to new broad neutral resonances produced in two-photon fusion and decaying to a top quark pair, γγ → $ t\overline{t} $. This is probed in central exclusive $ t\overline{t} $ production in proton-proton collisions, pp → $ pt\overline{t}p $. We use the tagging of the intact protons by PPS (CMS) and AFP (ATLAS) and consider the semi-leptonic $ t\overline{t} $ channel. The sensitivity is also mapped onto a set of dimension-8 $ \gamma \gamma t\overline{t} $ operators in the large mass limit. Using the kinematical correlations between the intact protons and the reconstructed $ t\overline{t} $ system, we obtain a sensitivity to the couplings of the dimension-8 operators of 1.4 10$^{−11}$ GeV$^{−4}$ at 95% CL. The sensitivity to the anomalous couplings is significantly improved down to about 7 10$^{−12}$ GeV$^{−4}$ if the proton time-of-flight is known with a precision of 20 ps in future measurements. The 95% CL sensitivity to broad neutral resonances reaches masses of order 1500 GeV when using timing information.