Cosmic-ray helium nuclei measurement with the calorimeter of the Alpha Magnetic Spectrometer

Purpose The distributions of energy responses of helium measured by the electromagnetic calorimeter (ECAL) of Alpha Magnetic Spectrometer (AMS-02) in Monte-Carlo do not agree with those in real data, thus using energy response matrix obtained from Monte-Carlo to measure the cosmic ray helium spectrum is not correct. Therefore, the spectrum measured with ECAL based on raw Monte-Carlo would be different from the real one. The purpose is to correct the response matrix to measure helium spectrum with ECAL. Methods The energy measured by ECAL of AMS-02 provides in-flight correction for the energy response matrix in Monte-Carlo. Results The spectrum based on corrected response matrix is consistent with the AMS collaboration published result. Conclusions It is feasible to measure helium spectrum with ECAL with corrected energy response matrix.