Speaker
Description
We will present studies evaluating the potential for the application of pulse shape discrimination (PSD) at high energy experiments using Thallium doped Cesium Iodide (CsI(Tl)) electromagnetic calorimeters, such as Belle II, in order to improve neutral hadron vs photon separation. Using 30 cm long CsI(Tl) crystals with PMT and PIN diode readout, the scintillation response for hadronic energy deposits is studied using proton test beams at TRIUMF with momenta ranging between 195-360 MeV/c and neutrons with kinetic energies up to 500 MeV. We show that in addition to the standard fast and slow scintillation components used to model photon pulses, the pulse shape variations observed for hadronic energy deposits in CsI(Tl) can be modelled using an additional scintillation component with a decay time of approximately $\tau_\text{hadron} = 560$ ns. By calculating the intensity of the hadronic scintillation component, neutron interactions containing combinations of secondary proton, deuteron and alpha particles are identified and separated from photon energy deposits with improved resolution compared to traditional charge ratio PSD methods. In addition, we have developed scintillation classes for GEANT4 to calculate the $\tau_\text{hadron}$ scintillation intensity as a function of the ionization density of the interacting particles. These simulations reproduce the hadronic CsI(Tl) response observed in the proton and neutron data. GEANT4 simulations are also used to study the expected improvement for neutral kaon long vs photon separation at CsI(Tl) calorimeters using PSD.
