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Abstract: The LHCf experiment is one of the LHC forward experiments. The aim is to measure the energy and the transverse momentum spectra of photons, neutrons and ''s at the very forward region (the pseudo-rapidity range of ), which should be critical data to calibrate hadron interaction models used in the air shower simulations. LHCf successfully operated at and proton–proton collisions in 2009 and 2010. We present the first physics result, single photon energy spectra at proton–proton collisions and the pseudo-rapidity ranges of and . The obtained spectra were compared with the predictions by several hadron interaction models and the models do not reproduce the experimental results perfectly. [Copyright &y& Elsevier]

Abstract: The inclusive photon energy spectra measured by the Large Hadron Collider forward (LHCf) experiment in the very forward region of LHC proton–proton collisions at are reported. The results from the analysis of 0.30 nb−1 of data collected in May 2010 in the two pseudorapidity regions of and are compared with the predictions of the hadronic interaction models DPMJET 3.04, EPOS 1.99, PYTHIA 8.145, QGSJET II-03 and SIBYLL 2.1, which are widely used in ultra-high energy cosmic ray experiments. EPOS 1.99 and SIBYLL 2.1 show a reasonable agreement with the spectral shape of the experimental data, whereas they predict lower cross-sections than the data. The other models, DPMJET 3.04, QGSJET II-03 and PYTHIA 8.145, are in good agreement with the data below 300 GeV but predict harder energy spectra than the data above 300 GeV. The results of these comparisons exhibited features similar to those for the previously reported data for collisions. [Copyright &y& Elsevier]

Abstract: Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers were measured at the SPS H4 beam line in 2007 using electron beams of 50–200GeV and muon beams of 150GeV. The absolute energy scale was determined in these data. The results that were obtained ( energy resolution) are well understood by using Monte Carlo simulations and are good enough for the requirements of the LHCf experiment. [Copyright &y& Elsevier]

Abstract: In early 2010, the Large Hadron Collider forward (LHCf) experiment measured very forward neutral particle spectra in LHC proton–proton collisions. From a limited data set taken under the best beam conditions (low beam-gas background and low occurrence of pile-up events), the single photon spectra at and pseudo-rapidity (η) ranges from 8.81 to 8.99 and from 10.94 to infinity were obtained for the first time and are reported in this Letter. The spectra from two independent LHCf detectors are consistent with one another and serve as a cross check of the data. The photon spectra are also compared with the predictions of several hadron interaction models that are used extensively for modeling ultra-high energy cosmic-ray showers. Despite conservative estimates for the systematic errors, none of the models agree perfectly with the measurements. A notable difference is found between the data and the DPMJET 3.04 and PYTHIA 8.145 hadron interaction models above 2 TeV where the models predict higher photon yield than the data. The QGSJET II-03 model predicts overall lower photon yield than the data, especially above 2 TeV in the rapidity range . [Copyright &y& Elsevier]

Abstract: The LHCf experiment aims to improve knowledge of forward neutral particle production spectra at the LHC energy which is relevant for the interpretation of air shower development of high energy cosmic rays. Two detectors, each composed of a pair of sampling and imaging calorimeters, have been installed at the forward region of IP1 to measure π 0 energy spectra above 600GeV. In this paper, we present a Monte Carlo study of the π 0 measurements to be performed with one of the LHCf detectors for proton–proton collisions at TeV. In approximately 40min of operation at luminosity during the beam commissioning phase of LHC, about 1.5×104 π 0 events are expected to be obtained at two transverse positions of the detector. The backgrounds from interactions of secondary particles with beam pipes and interactions of beam particles with residual gas in the beam pipes are expected to be less than 0.1% of the signal from π 0s. We also discuss the capability of LHCf measurements to discriminate between the various hadron interaction models that are used for simulation of high energy air showers, such as DPMJET3.03, QGSJETII-03, SIBYLL2.1 and EPOS1.99. [Copyright &y& Elsevier]