Performance of the photon spectrometer TAPS for deep subthreshold pion detection

We present in this paper the characteristics of the BaF2 spectrometer, TAPS, which allow to detect rare electromagnetic events in a high hadronic background. The case of deep subthreshold pions produced in 36Ar+197Au collisions at 25A and 35A MeV, in which the pion signal is much weaker than the hadronic background and comparable to the cosmic ray background, is studied.