Search for exclusive diphoton production with intact protons in PPS

A search for high-mass exclusive diphoton production via photon-photon fusion with tagged protons is presented. The analysis utilizes 102.7 $\mathrm{fb}^{-1}$ of data collected by the CMS and TOTEM Precision Proton Spectrometer in the 2016, 2017, and 2018 LHC runs. Events are selected that have two photons with high transverse momenta that are back-to-back in azimuth and with a large diphoton invariant mass. To remove the dominant backgrounds, tagged final state protons from the event are required to match the kinematics of the final state photons. Only events having opposite-side protons within an asymmetric fractional momentum loss between 0.035 and 0.15 (0.18) for the detectors on the negative (positive) side of CMS are considered. One exclusive diphoton candidate is observed for an expected background of 1.1 events. Limits at $95\%$ confidence level are derived on the four-photon anomalous coupling parameters for $|\zeta_1|$ $<$ 7.3 $\times$ 10$^{-14}$ $\mathrm{GeV}^{-4}$, $|\zeta_2|$ $<$ 1.5 $\times$ 10$^{-13}$ $\mathrm{GeV}^{-4}$ using an effective field theory. Additionally, axion-like particles are excluded in the mass range of 500 to 2000 GeV.