LHCf Run II physics results in proton-proton collisions at $\sqrt{s}$ = 13 TeV

International audienceThe LHC-forward experiment (LHCf), located at the Large Hadron Collider (LHC), is designed tomeasure the production cross section of neutral particles in the very-forward region, covering thepseudorapidity region above 8.4 (up to zero-degree particles). By measuring the very-forwardparticle production rates at the highest energy possible at an accelerator, LHCf will providefundamental informations to improve phenomenological hadronic interaction models used in thesimulation of air-showers induced by ultra-high-energy cosmic rays in the atmosphere. Theexperiment consists of two small independent detectors placed 140 metres away from the ATLASinteraction point (IP1), on opposite sides. Each detector is made of two sampling and positionsensitive calorimeters.This contribution will focus on the Run II physics results of LHCf in proton-proton collisions at 13TeV. At first the photon energy spectrum will be presented and compared with the predictions ofseveral hadronic interaction models. The advantages of the ATLAS-LHCf combined analysis willthen be discussed and the preliminary spectrum of very-forward photons produced in diffractivecollisions (tagged by ATLAS) will be shown together with models predictions. The preliminaryFeynman-x and transverse momentum spectrum of $\pi^0$, and the Feynman-x spectrum of $\eta$ will alsobe presented. Photons and $\pi^0$ production cross section provides important information about theelectromagnetic component of an air-shower, while $\eta$ measurements give the possibility to probethe strange-quark related contribution. Finally, the neutron energy spectrum measured in severalpseudorapidity regions will be shown and compared with the predictions of various hadronicinteraction models. From these measurements the average inelasticity of the collisions, whichstrongly affects the development of an air-shower, has also been extracted