Particle identification with LHCf Arm#1 detector

LHCf (LHC forward) is an experiment to measure neutral particles emitted in the very forward region of LHC collisions. The collision energy corresponds to 10¹⁷eV pp collision in the laboratory system. Although the highest cosmic ray energy lies still far beyond, we expect collisions at LHC will give us an important clue to understand high energy cosmic ray phenomena. Through our test experiments and calculations, we showed the LHCf experiment can verify various interaction models employed in Monte Carlo simulation which is an indispensable tool to study cosmic-rays. In this paper, we focus our attention on the particle ID capability of LHCf. LHCf will measure the energy and transverse momentum spectra of incoming high energy photons and neutrons. Therefore it is crucial for LHCf to have high capability of distinguishing those two neutral particles. This is shown by analyzing a CERN SPS beam test data along with Monte Carlo simulations. Since electrons and photons, or protons and neutrons behave in an almost similar way in the detector, we investigated a rejection power of protons from electrons by a beam test at CERN SPS. It is found that LHCf Arm#1 detector has a good performance (more than 99% rejection power of hadron). The same rejection method was applied to Monte Carlo simulation events to find consistent results with the experimental data. MC simulations at LHC energies were also performed; a good rejection power which is enough for accomplishing the objective of the LHCf experiment is confirmed.