# New Inorganic Scintillators' Application in the Electromagnetic Calorimetry in High-Energy Physics
## 2 Simulations in Geant4  
A computer program based on the Geant4 [17] package was developed to determine the energy resolution and other features of electromagnetic calorimeter models. The program allows for calculations in the case of both a calorimeter with only one type of crystal and the case of a compound calorimeter with GAGG and PWO crystals arranged in series. The simulation uses a calorimeter assembly of 11 \(\times\) 11 crystals in a steel honeycomb structure with a wall thickness of 0.01 cm. In the case of the compound calorimeter, GAGG crystals of the following lengths were examined: 0.5, 1.5, 3, 5, and 10 cm (see example layouts in Figure 2); the length of the PWO section was 18 cm (such crystals are used in the PHOS calorimeter). The cross-section of the crystals in both cases was 22 \(\times\) 22 mm\({}^{2}\). The energy released in each section was calculated, then recalculated into the photodetector signal according to the light yield value. Separate photodetectors were proposed for each segment. The primary particle's entry point was evenly distributed over the surface of the calorimeter's central crystal. Photons with energy levels ranging from 100 keV to 100 GeV were examined.  
An optional value of the deposited energy in each crystal was modified to provide a more realistic description of the calorimeter:  
1. Light yield simulation: the number of photons on the photodetector changes according to the Poisson distribution, with mean values of 420 phe/MeV and 6 phe/MeV for  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Property** & **Gd3 Al2 Ga3O12:Ce** & **PbWO4** & **Lu3 Al5O12:Ce** & **Lu2 SiO5:Ce** & **NaI:T1** & **CsI:T1** \\  & **(GAGG)** & **(PWO)** & **(LuAG)** & **(LSO)** & **NaI:T1** & **CsI:T1** \\ \hline Density, g/cm\({}^{3}\) & 6.68 & 8.28 & 6.73 & 7.4 & 3.67 & 4.53 \\ Wavelength of & & 530 & 520 & 535 & 420 & 415 & 550 \\ \(\mathrm{X_{0}}\), cm & 1.59 & 0.89 & 1.30 & 1.10 & 2.60 & 1.86 \\ Light yield, & & & & & & \\ photons/MeV & 50,000 & 100–300 & 25,000 & 30,000 & 40,000 & 54,000 \\ Decay time, ns & 95 & 20 & 70 & 70 & 230 & 680 \\ Hygroscopicity & None & None & None & None & Strong & Slight \\ \hline \end{tabular}
\end{table}
Table 1: Properties of inorganic scintillation crystals.  
Figure 2: Schematic variants of GAGG and PWO crystal arrangements with photodetectors: green— photodetector, red—insulator, blue—GAGG crystal, yellow—PWO crystal.  
GAGG crystals and PWO crystals in the case of APD 5 \(\times\) 5 mm\({}^{2}\) at T = -25 \({}^{\circ}\)C (for a convenient comparison with test beam measurements using PHOS [18]), respectively, and then recalculated back into energy;
2. Emulation of the noise of electronics, which was modeled as a random Gaussian distribution with parameters \(\mu\) = 0 and \(\sigma\) = 5 MeV (high noise) or \(\sigma\) = 1 MeV (low noise) and then added to the energy released in each cell;
3. Cuts to the minimum energy in a cell: only those cells with an energy release above some set threshold (10 MeV for high noise; 2 MeV for low noise) were included;
4. Clustering: as in the ALICE analysis and simulation package, AliROOT [2], a cell was discarded if it did not have at least one vertex in common with the rest of the cluster.