Application of the Prony least squares method for fitting signal waveforms measured by sampling ADC Free

In the future CBM experiment at FAIR and in the MPD experiment at NICA as well as in the existing BM@N experiment forward hadron lead/scintillator sampling calorimeters will be used for geometry determination in heavy ion collisions. Digitizing of an analog signal with sampling ADCs used for signal readout in these calorimeters leads to significant fluctuation of the measured charge, if the charge is rather small. Such fluctuations can be caused by noise, pick-up, signal pile-up, as well as a small number of ADC samples per signal. To improve the response of the calorimeters, the new procedure of fitting signals based on the Prony least squares method has been developed. This method represents waveform as a linear combination of exponential functions and allows to obtain the charge more accurately requiring minimum machine time. The application of this method for the processing of signals, obtained in hadron calorimeter tests with cosmic muons and at hadron beams at CERN using sampling ADC board ADC64s2 (AFI Electronics, Dubna) is demonstrated. It is shown that fitting of the signals with a known function allows to extract weak signals comparable to the level of electronic noise, which is important for performing a muon calibration of calorimeter sections.