Performance of the prototype detector for the LHCf experiment

LHCf is a compact experiment for measuring the energy and transverse momentum spectra of the neutral particles emitted in the high rapidity range at an LHC interaction point. The data obtained by LHCf will set a crucial anchor point for calibration of the interaction models used in studies of high-energy cosmic-rays. In this paper, we report results of a beam test of an LHCf prototype detector that was carried out in July-August 2004 at the CERN SPS H4 beamline. We measured electromagnetic showers generated by 50-200 GeV electron primary beams and obtained 3-5% energy resolution as a function of the primary energy. The measured resolution is in good agreement with Monte Carlo simulations. The position resolution of SciFi hodoscope for measurement of the shower axis, 0.12-0.17 mm, was slightly worse than the MC expectation but adequate for the requirements of LHCf. This study gives a firm foundation for final design and fabrication of the LHCf detectors which will be installed in LHC in 2007 and operational in the early stages of LHC commissioning.