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

PurposeThe 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.
MethodsThe energy measured by ECAL of AMS-02 provides in-flight correction for the energy response matrix in Monte-Carlo.
ResultsThe spectrum based on corrected response matrix is consistent with the AMS collaboration published result.
ConclusionsIt is feasible to measure helium spectrum with ECAL with corrected energy response matrix.