A parameterized energy correction method for electromagnetic showers in BGO-ECAL of DAMPE

Abstract

DAMPE is a space-based mission designed as a high energy particle detector measuring cosmicrays and γ−rays which was successfully launched on Dec.17, 2015. The BGO electromagnetic calorimeter is one of the key sub-detectors of DAMPE for energy measurement of electromagnetic showers produced by e ± /γ. Due to energy loss in dead material and energy leakage outside the calorimeter, the deposited energy in BGO underestimates the primary energy of incident e ± /γ. In this paper, based on detailed MC simulations, a parameterized energy correction method using the lateral and longitudinal information of electromagnetic showers has been studied and verified with data of electron beam test at CERN. The measurements of energy linearity and resolution are significant improved by applying this correction method for electromagnetic showers.

Measurement of absolute energy scale of ECAL of DAMPE with geomagnetic rigidity cutoff

“…At last, absolute energy scale of MIPs will be determined by carefully on-orbit Monte Carlo simulation. Although verification of simulation shows a well agreement with flight data [3], proton MIPs events can only determine absolute energy scale at very low energy range (MPV of proton MIPs in BGO is ∼23MeV), and so many factors can affect this kind of energy reconstruction at high energy range. Therefore, measurement of absolute energy scale is an essential job for energy or spectrum measurement.…”

“…Each crystal is read out from both ends with 3 dynodes of PMT, modifying signal with low, middle and high gains to cover three different overlapped energy ranges, which means one fluorescence signal especially for dozens GeV range can be measured at least four times(2 ends & 2 dynodes). By this design, the energy resolution can reach 1 − 2% [3] at dozens GeV. A major advantage of DAMPE's absolute energy scale measurement is that DAMPE has better energy resolution comparing with Fermi-LAT (about 7% energy resolution at 13GeV [7]).…”

“…A series of empirical formula [3] are used to correct energy deposited in insensitive matter and leakage from back and side. At last, absolute energy scale of MIPs will be determined by carefully on-orbit Monte Carlo simulation.…”

“…This algorithm is meant to equalize the response of each crystal read-out dynode and to convert the ADC signal to energy via the calibration constants derived from cosmic-ray proton MIP events and DAMPE's calibration electronics circuits. In procedure of Reco, energy hits are reconstructed to final energy by a series of correction algorithms, including side and back end energy leakage correction and dead zone correction [3]. These algorithms are all verified by beam test at CERN in 2014 and 2015 [1].…”

Studies of Cosmic-Ray Proton Flux with the DAMPE Experiment

“…A digitization algorithm including the DAMPE detector response is developed for converting the raw energy hits by GEANT4 simulations into Analog-to-Digital Converter (ADC) counts. Then we apply the reconstruction algorithm to the simulation data to obtain the reconstructed events [17]. An isotropic, single powerlaw proton spectrum is simulated and then the effective acceptance of the i−th primary energy bin is obtained by…”