Speakers
Description
The main purpose of the Large Hadron Collider-forward (LHCf) experiment is to study the secondary particle spectrum in the very forward region of high-energy hadronic collisions at the LHC. The LHCf measurements play an important role in calibrating the hadronic interaction models used to simulate Extensive Air Showers (EAS), which originate from interactions between cosmic rays and atmospheric nuclei. Specifically, the LHCf experiment measures neutral particles—such as neutrons, photons, $\pi^0$, and $\eta$ mesons—produced in the very forward region of LHC primary collisions, which are highly relevant to the development of EAS.
Furthermore, LHC proton-proton collisions at a center-of-mass energy of 13.6 TeV are equivalent, in the fixed-target frame, to the interaction of a proton of nearly $10^{17}$ eV with a proton at rest.
These considerations lead to the conclusion that the LHC can effectively reproduce the scenario of a hadronic interaction between a very high-energy cosmic proton and a nucleon in an atmospheric nucleus. With the LHCf experiment, it is therefore possible to measure the production rates of neutral particles that most significantly influence the development of the corresponding EAS.
Since the start of LHC operations, the LHCf experiment has collected data from proton-proton collisions at several center-of-mass energies, ranging from 0.9 TeV to 13.6 TeV, as well as from proton-lead collisions at nucleon-nucleon center-of-mass energies of 5.02 TeV and 8.1 TeV. The main results include measurements of $\pi^0$, neutron, and $\eta$ meson production rates in the very forward region. Some of these results will be presented in this contribution, along with comparisons between LHCf experimental data and theoretical predictions from the most commonly used hadronic interaction models in air shower simulations.
In July 2025, the LHCf experiment completed its final data-taking operation with proton–oxygen collisions at a nucleon-nucleon center-of-mass energy of 9.6 TeV. This configuration closely reproduces the interaction between high-energy cosmic protons and atmospheric nuclei and is therefore of particular relevance for cosmic-ray physics. Compared to proton–proton and proton–lead data, proton-oxygen collisions are expected to significantly reduce extrapolation uncertainties, offering improved constraints on hadronic interaction models used in air-shower simulations.
This contribution will review the current status of the LHCf results and present the latest updates and ongoing analyses on the proton–oxygen run.