TOT method for the disentanglement of photons in positron annihilation lifetime spectroscopy

The Jagiellonian Positron Emission Tomograph (J-PET) is a multidisciplinary device aiming to perform studies in medical field as well as to test the fundamental symmetries. The plastic scintillators offer very good time resolution. Although, due to the low atomic number of the plastic material, the incident photons interact mainly via the Compton effect. Thus instead of full energy deposition by the photon, there is a range of energy depositions depending on its scattering angle. For the positron annihilation lifetime spectroscopy studies, it is necessary to distinguish the photons emitted from different processes. Therefore, it becomes crucial to find a method to disentangle the photons of different energies. In the present work, the control spectra are discussed which can unambiguously categorize the photons of different energies and origins, which are essential for the studies based on the positronium lifetime.