Physics potential of a combined data taking of the LHCf and ATLAS Roman Pot detectors

The modelling of hadronic showers induced by cosmic rays scattering off atmospheric nuclei is currently a major source of systematic uncertainties for Cherenkov telescope analyses. However, it is in principle possible to study similar soft inelastic scattering processes under laboratory conditions in proton-proton collisions at the LHC. This requires the presence of detectors in the ultra-forward region. The LHCf detector covers the zero-degree angle for neutral particles, while the ATLAS Roman Pot detectors (AFP and ALFA) can detect scattered protons at small angles close to the passing beam. Until now, these two detection approaches have only been used separately. However, the process selection and event reconstruction could be improved if both the neutral particle and the proton information could be recorded simultaneously. In this note the feasibility of a combined data taking during a special run with low instantaneous luminosity at a center-of-mass energy of 13.6 TeV is investigated based on simulations. The combined acceptances for the LHCf and ATLAS Roman Pot detectors are determined for three kinds of soft QCD processes: Single diffractive dissociation and the exclusive production of a $\Delta^{+}(1232)$ baryon or an $𝑁 (1440)$ baryon by proton excitation. The results indicate that the expected event rates are in all cases higher for the combination of LHCf and AFP than for LHCf and ALFA, given the beam conditions during the special run. During the special run approximately 5.7 million events with a signal in both LHCf and AFP were recorded, resulting in a unique data set for a future analysis of diffraction events.