One major goal of the future FAIR 1 facility is the understanding of the structure of matter at a sub-nuclear level which is governed by a short range force, the strong interaction. The state-of-the-art PANDA 2 detector at FAIR will be used to study the strong interaction by investigating proton - antiproton interactions. The EMC 3 of the target spectrometer with its expected excellent performance and efficiency for elec- tromagnetic probes over a wide energy range from 10 MeV up to 15 GeV, will be one of the central components to achieve the physics goals. The Barrel part of the EMC will consist of more than 11,000 lead tungstate crystals operated at −25 ◦ C to achieve the requirements of the experiment. Within the scope of this work, the performance of the most recent prototypes of the PANDA Barrel EMC will be compared. The first large scale prototype PROTO60 was designed to test the performance of the improved tapered lead tungstate crystals. The PROTO60 which consists of 6 × 10 crystals was tested at various accelerator faci- lities over almost the complete envisaged energy range but missing the mid energy range. The results were fulfilling the requirements of the TDR of the PANDA EMC in terms of energy, position and time resolution. Therefore, the resolution parameters were used as input parameters for the physics simulations of the research program of PANDA. Hence, the PROTO60 results represent a specification limit. However, com- plementary results of a beamtime time for the mid energy range will be presented in this work so as to additionally verify the previous results. Despite the sufficient performance of the PROTO60, a second prototype PROTO120 has been constructed, in order to realize the final barrel geometry and to test the final front-end electronics. It represents a larger section of a barrel slice, containing the most tapered crystals and the close to final components for the PANDA EMC. The emphasis of this work is the optimization of the Barrel EMC with respect to the front-end electronics. A significant improvement is out of reach because the essenti- al parameters influencing the performance of the Barrel EMC like the quality of the envisaged lead tungstate crystals and the pre-amplifier have been improved signifi- cantly and reached its limits. However, the performance of the specially developed pre-amplifier of the Barrel EMC has not been verified under experimental conditions so far. Therefore, a beamtime test has been conducted with the PROTO120, which will be presented within this work. Furthermore, possibilities to optimize the perfor- mance will be discussed. Another main goal of this work is the unique study of the impact of dead material in front of the PROTO60. The experiment with prototype detectors are performed under idealized conditions. But the material budget in front of the Barrel EMC is conside- red to have a significant influence on the performance for future operation within the PANDA detector. Therefore, the performance of the PROTO60 with a quartz plate in front has been measured. Results will be discussed within this work.

Die vorliegende Dissertation besteht aus zwei Teilen: Im ersten Teil wird eine Analyse der Kanäle χc₂ → π⁺π⁻/K⁺K⁻ in radiativen ψ(2S) –Zerfällen präsentiert. Die Daten wurden dabei im Rahmen des BESIII-Experimentes aufgenommen. Es wurden die Multipolamplituden des radiativen Zerfalls und die Verzweigungsverhältnisse der χc₂ – Zerfälle bestimmt. Die Ergebnisse deuten auf ein verschwindendes anomales magnetisches Moment des Charm-Quarks sowie auf eine nicht-vorhandenen S-D-Mischung der ψ(2S)-Resonanz hin. Im zweiten Teil wird die Entwicklung eines Monitorierungssystems auf Basis eines Lichtpulsers zur Überwachung der Kristalle und der Ausleseelektronik für das elektromagnetische Kalorimeter des P¯ANDA- Experimentes vorgestellt. Neben Schaltplänen der Elektronik wird die mechanische Integration des Systems in der Vorwärtsendkappe des elektromagnetischen Kalorimeters präsentiert.

The proton electromagnetic form factors (FF) in the space-like region (q2 < 0) have been measured for multiple decades using electron{proton scattering and Rosenbluth separation method. Recently developed polarization transfer technique resulted in a dierent value of extracted FF. It was suggested that the previously unaccounted hard two-photon exchange (TPE) eect, can be responsible for the discrepancy. The OLYMPUS experiment performed a high precision measurement of the TPE contribution via measurement of the positron to electron elastic scattering cross section ratio. It was performed at DESY using 2 GeV electron and positron beams and the BLAST spectrometer. A crucial part of the experiment was precise measurement of the integrated luminosity. The symmetric Moeller/Bhabha luminosity monitors, which were designed and built in Mainz, used Mller and Bhabha processes for luminosity measurements. The analysis of the collected SYMB data is presented in this work. In the time-like region, where q2 > 0, form factor data is scarce and only the ratio of electric to magnetic form factor have been measured so far. The PANDA experiment will be able to measure individual electric and magnetic time-like FF. Extensive feasibility studies of the proton form factor measurement have been performed using PandaRoot simulation framework. This include the signal pbar p -> e+e- selection, the main background pbar p -> pi+ pi- suppression, and investigation of possible sources of systematic uncertainties in the q2 range between 5.4 GeV^2 and 13.9 GeV^2. The estimated statistical and systematic accuracy of the proton FF extraction at PANDA is 2%-57%.