Speaker
Description
We report the first observation of the production of high-transverse-momentum jets and electroweak bosons in association with a tagged forward proton in proton–proton collisions at a center-of-mass energy of 13.6 TeV. The analysis uses 2.0 fb(^{-1}) of data collected by the CMS experiment during dedicated low-pileup LHC operation in 2026. Forward protons carrying 85–97% of the beam energy are reconstructed with the CMS Precision Proton Spectrometer and associated with centrally produced W bosons, Z bosons, or multijet systems. The signal is established through the observation of significant forward–backward asymmetries of the central system with respect to the tagged-proton direction, providing direct evidence that the proton originates from the same hard interaction. The production of W and jet events with a tagged forward proton is observed with significances exceeding five standard deviations, while the Z-boson channel is observed with a significance above three standard deviations. Fiducial tagged-proton fractions are measured inclusively and differentially as functions of jet multiplicity, W-boson charge, and multijet invariant mass, extending to central-system masses above 2 TeV. The measured rates are found to be significantly larger than predictions from current hard-diffractive models, providing new constraints on the description of diffraction and color-singlet exchange at the highest momentum transfers accessible at the LHC.