The electromagnetic calorimeter of the $\overline{P}ANDA$ detector. Prototype measurements and simulations

In the Standard Model of particle physics, quantum chromodynamics (QCD) describes the interaction of quarks and gluons. The strong interaction produces an abundance of bonding states, the hadrons. Most of the hadrons known so far can be described as a bonding state of three quarks or one quark and one antiquark. In recent years, however, some states such as the χ${}_{c1}$(3872) or the Z${}_c$(3900)${}^{\pm }$ have been discovered that do not fit into this simple picture. By measuring antiproton-proton collisions at a momentum of up to 15 GeV/c, the Panda experiment will help to significantly improve the understanding of the binding states of the strong interaction and thus of QCD in the non-pertubative regime. The reaction products produced in the annihilation will be measured with a sophisticated detector system. The detector system is composed of specialized subdetectors that perform different tasks. Electromagnetic calorimeters are used to determine the energy of electrons and the energy and direction of photons. The calorimeter located in the target spectrometer of the experiment will consist of about 15500 lead tungstate crystals. The scintillation light from the crystals will be converted into electrical signals by APDs and VPTTs. These are digitized by SADCs. In this work, measurements were evaluated using two prototypes for the calorimeter. A photon beam was used to determine the energy resolution for energies up to 1440 MeV. A resolution of 2.5% was achieved at an energy of 1 GeV. In addition, the simulation of the calorimeter was extended to include the position dependence of the light output in the crystal. This was identified as an important contributor to the energy resolution. In measurements with an electron beam, the spatial resolution at energies from 5 GeV to 15 GeV was also investigated. The resolution achieved ranged from 0.9 mm at high energies to 2.2 mm at low energies. These and other test measurements have shown that a lead tungstate crystal calorimeter is suitable for the Panda experiment calorimeter. In all measurements, it has been shown that it is very important to position the detectors accurately and to determine precisely the deviations from the desired position. Therefore, special attention must be paid to this when setting up the calorimeter modules and installing them in the detector. In a simulation of the decay Z${}_c$(3900)${}^0$ → J/Ψπ${}^0$ → μ${}^{+}$μ${}^{-}$γγ, the entire detector system for measuring neutral and and charged particles was considered and an estimate of the required measurement time was made. The $\overline{p}p$ → π${}^{+}$π${}^0$π${}^{-}$ reaction was identified as the largest background contribution. This example was used to demonstrate that Panda will be able to contribute decisively to the spectroscopy of even exotic states.