The Precision Proton Spectrometer (PPS) was developed by the CMS and TOTEM Collaborations and started to be used extensively during Run 2 of the LHC. It is a powerful tool for advancing new measurements with forward proton tags and beyond the standard model searches. The commissioning of this new detector involves understanding different aspects of forward proton reconstruction (alignment and optics calibrations, radiation damage, pileup contributions and validation using standard model candles).

In this seminar I'll illustrate how PPS can be used by focussing on a generic search for the associated production of a Z boson or a photon with an additional unspecified massive particle X in proton-tagged events from proton-proton (pp) collisions at √s =13 TeV, recorded in 2017.  The so-called missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant resonant deviations in data with respect to the background predictions have been observed. Model-independent upper limits on the visible production cross section of pp → pp + Z/γ + X are set. Results from other recent searches with PPS and Run 2 will also be summarized.