The differential cross sections for inclusive neutral pions as a function of transverse and longitudinal momentum in the very forward rapidity region have been measured at the Large Hadron Collider (LHC) with the Large Hadron Collider forward detector (LHCf) in proton-proton collisions at √ s = 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of √ sNN = 5.02 TeV. Such differential cross sections in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. Comparing proton-proton with protonlead collisions, we find a sizable suppression of the production of neutral pions in the differential cross sections after subtraction of ultra-peripheral proton-lead collisions. This suppression corre-arXiv:1507.08764v3 [hep-ex]

The Large Hadron Collider forward (LHCf) experiment was motivated to understand the hadronic interaction processes relevant to cosmic-ray air shower development. We have developed radiation-hard detectors with the use of Gd2SiO5 (GSO) scintillators for proton-proton √s = 13 TeV collisions. Calibration of such detectors for photon measurement has been completed at the CERN SPS T2-H4 line in 2015 using electron beams of 100–250 GeV and muon beams of 150–250 GeV . After the channel-by-channel absolute energy calibration, the energy resolution of the calorimeters is confirmed to be better than 3% for electrons with energy above 100 GeV . The position dependence of the energy scale of the calorimeters was reduced to the level of 1% after the corrections for scintillator nonuniformity and the shower leakage effect. The position resolution of the new shower imaging detector, a GSO-bar hodoscope interleaved in the calorimeter, was 100 μm for 200 GeV electrons. The experimental results are well explained by Monte Carlo simulations. We have confirmed that the new detectors meet the requirement of the LHCf experiment at √s = 13 TeV.

The LHCf experiment is an LHC experiment dedicated to measure the production spectra of forward neutral particles, photons, π 0 s and neutrons. The obtained results are very useful to test hadronic interaction models which are used in MC simulations for cosmic-ray air shower developments. The LHCf had an operation in 2015 with p-p collisions at √ s= 13 TeV, which corresponds to the collision energy of 0.9 × 10 17 eV in the laboratory frame. We discuss the results of the inclusive energy spectra for forward photons obtained at p-p, √ s= 13 TeV data as well as π 0 results taken at p-p, √ s= 7 TeV. In addition we introduce future prospects of LHCf analyses and activities.

Abstract. The LHCf experiment is one of the LHC forward experiments. The aim of LHCf is to provide critical calibration data of hadronic intraction models used in air shower simulations. The LHCf has completed the operations for p-p collisions with a collision energy of √ s = 0.9 and 7 TeV p-p in 2010 and for p-Pb collisions with a collision energy per nucleon of √ s N N = 5.02. The recent LHCf result of forward neutron energy spectra at 7 TeV p-p collision and forward π 0 spectra at p-Pb collisions are presented in this paper. LHCf experimentThe LHCf experiment is an LHC experiment dedicated to the measurement of very forward neutral-particle spectra. The aim is to provide critical date for the calibration of hadronic interaction models used in MC simulations of cosmic-ray induced air showers. One of the key parameters of air shower development is the energy spectra of the energetic secondaries produced in the forward region of hadronic interactions. The LHCf detectors were designed to measure such forward energetic particles of p-p and pPb collisions at an LHC interaction point. The pseudorapidity coverage of the detectors is more than 8.4 at the beam crossing angle of 140 µrad.The LHCf has two independent detectors, so called Arm1 and Arm2, which were installed +/− 140 m from the ATLAS interaction point (IP1). Each detector has two sampling and imaging calorimeter towers. They consist of tungsten plates, 16 scintillator layers and four position sensitive layers. The scintillator layers were inserted between tungsten plates for shower sampling with 2 radiation length step. The position sensitive layers were developed to measure the shower impact position with different techniques of X-Y scintillating a e-mail: menjo@stelab.nagoya-u.ac.jp fiber hodoscopes and X-Y silicon strip detectors for Arm1 and Arm2, respectively. The transverse cross sections of calorimeters are 20×20 mm 2 and 40×40 mm 2 in Arm1 and 25×25 mm 2 and 32×32 mm 2 in Arm2. The total thickness of calorimeter towers is 44 radiation lengths and 1.7 interaction length. The LHCf detectors are able to measure only neutral particles like photons and neutrons because the charged particles produced at IP1 are swept out by the magnetic field of dipole magnets located between IP1 and the LHCf detectors. The energy resolution of detectors is about 5% for photons and 40% for neutrons. The position resolution is better than 200 µm for photons and a few mm for neutrons. More details of the detector performance were reported elsewhere [1,2].The LHCf has successfully completed operating with proton-proton collisions at √ s = 0.9, 7 TeV in 2010 and with proton-lead collisions at √ s N N = 5.02 TeV in 2013. The forward photon and π 0 spectra for proton-proton collisions has been published [3][4][5]. Neutron spectrum in √ s = 7 TeV p-p collisionsThe measurement of the neutron energy spectrum is a way to access one of the key parameters for air-shower This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which p...

Abstract. The LHCf experiment, optimized for the study of forward physics at LHC, completes its main physics program in this year 2015, with the proton-proton collisions at the energy of 13 TeV. LHCf gives important results on the study of neutral particles at extreme pseudo-rapidity, both for proton-proton and for proton-ion interactions. These results are an important reference for tuning the models of the hadronic interaction currently used for the simulation of the atmospheric showers induced by very high energy cosmic rays. The results of this analysis and the future perspective are presented in this paper.