The performance of LHCf detector

In cosmic ray physics, the uncertainty of the hadron interaction model causes systematic errors of air shower simulations in high‐energy region. To solve the problem, the LHCf experiment measures energies and transverse momenta of neutral particles emitted in the forward region of 14 TeV p‐p collision at CERN LHC. Two LHCf detectors, consisting of sampling and imaging calorimeters, are installed at zero degree collision angle at + 140 m from the interaction point 1 (IP1). The energy resolution is confirmed as to be <5% and the position resolution <0.2 mm for gamma‐rays with energies from 100 GeV to 200 GeV by test beam results at the CERN SPS. Use of the Front Counter reduces the beam‐gas background by a factor 50.