[en] Within the A4 experiment the contributions of the strange quark to the electromagnetic form factors of the proton are measured. These see-quark effects in low energy observables are very important for the understanding of hadron structure, because they are a direct manifestation of QCD degrees of freedom in the non-perturbative regime. Linear combinations of the strangeness vector form factors of the proton (G_E^s and G_M^s) are accessible experimentally by measuring the parity violating asymmetry in the cross section of the elastic scattering of longitudinal polarised electrons off unpolarised nucleons. Two such measurements were published by the A4 collaboration before this work. Both of them were forward angle measurements at the Q² values of 0.23 and 0.10 (GeV/c)², respectively. A measurement at backward angle with a beam energy of 315 MeV was performed for separating G_E^s and G_M^s at the higher of these Q² values. In the A4 experiment a longitudinally polarised electron beam scatters on a liquid hydrogen target. Single scattered electrons are counted with a Cherenkov calorimeter. The separation of elastic from inelastic events is achieved by means of calorimetric energy measurement. For the backward angle measurement a plastic scintillator was installed as electron tagger for suppressing the γ background coming from the decay of π⁰ mesons. In order to make the data analysis possible the energy spectra needed to be studied thoroughly. This was done in this work using detailed simulations of both the scattering processes suffered by beam electrons and of the response of the detectors. A method for handling the remaining background due to γ conversion before the scintillator has been also developed. The simulation results agree with the measured spectra at the 5% level and the strategy for handling the background was shown to be feasible. The asymmetry value obtained by handling the background as proposed in this work was combined with the previous A4 forward angle measurement at the same Q² for separating G_E^s and G_M^s at Q²=0.22∝(GeV/c)². The results are G_M^s= -0.14 ± 0.11_exp ± 0.11_theo and G_E^s= 0.050 ± 0.038_exp ± 0.019_theo, where the systematic uncertainty due to the background correction is contained in the experimental error. Conclusions about the influence of strangeness on the static electromagnetic properties of the proton are drawn from these results and are presented at the end of the work. (orig.)

[en] A measurement of the parity violation (PV) asymmetry in electron-proton scattering using a polarised electron beam is performed at MAMI. The experimental apparatus is able to detect electrons, that are scattered exciting the Δ(1232) resonance. In order to study the PV in such process, it is important to understand the energy spectrum in the corresponding region. The aim of this work is a simulation including all relevant processes in order to extract an estimate of the PV asymmetry in the Δ(1232) region. (orig.)

[en] A sample of recent results in muon scattering measurements from the COMPASS experiment at CERN will be reviewed. These include high energy processes with longitudinally polarised proton and deuteron targets. High energy polarised measurements provide important constraints for studying the nucleon spin structure and thus permit to test the applicability of the theoretical framework of factorisation theorems and perturbative QCD. Specifically, latest results on longitudinal quark polarisation, quark helicity densities and gluon polarisation will be reviewed.

[en] Backward angle measurements with the A4 setup at Mainz have been performed and are ongoing. Differently as with the forward measurements severe background issues had to be faced, due to γ-events generated by the π⁰ decay. Hardware upgrades as well as data analysis improvements were needed. For the latest a detailed study of the background by means of Monte Carlo simulations has been undertaken. Its major features together with the basic ansaetze of the γ-background handling are presented in this contribution.

No abstract available

[en] The PANDA experiment at the FAIR facility will be a multipurpose hermetic spectrometer covering the full solid angle range. A key role for several physics cases will be played by the electromagnetic calorimeter. This includes ca. 15000 PbWO₄ scintillating crystals arranged in a central barrel, a forward and a backward end-cap. The backward end-cap of the PANDA electromagnetic calorimeter is composed by 540 straight crystals covering the scattering angles between 147 ^circle and 161 ^circle. They are housed in the so-called alveoli which are carbon fibre boxes, providing both strength and low material budget. The crystals are to work at -25 C in order to improve the light yield. To achieve this temperature a cooling system and thermal insulation are needed. The cooling system removes the heat coming from the electronics and through walls, cables and mechanical supports. Vacuum insulated panels are installed as a thermal shielding. Avalanche Photodiodes (APD) have been chosen as photon detectors, since they are still functional under strong magnetic fields. ASIC chips will be used to amplify the APD signal, this preamplifier features low noise and low heat generation. Due to the weight of this detector, it will be supported from the outside of the PANDA target spectrometer in a counter lever arm position.

[en] One of the main goals of the future PANDA experiment at FAIR (Darmstadt, Germany) is the investigation of the proton structure. Electromagnetic form factors (FF's) are fundamental quantities which parameterize the electric and magnetic structure of hadrons. In the time-like region, proton FF's can be accessed experimentally in anti pp → l⁺l^- (l = e,μ) annihilation processes, assuming that the interaction takes place through the exchange of one virtual photon. The expected statistical precision for the measurement of time-like electromagnetic proton form factors with PANDA was investigated in the framework of the PANDARoot software for detector simulation and event reconstruction for both muon and electron channels. These studies investigated the possibility to achieve an optimal signal-background separation and sufficient background suppression of the relevant background channels. Different methods have been used to generate and analyse the processes of interest. The results show, that time-like electromagnetic proton form factors can be measured at PANDA with high statistical accuracy over a large kinematical region.

[en] The PANDA experiment at the new FAIR facility will cover a broad experimental programme in hadron structure and spectroscopy. As a multipurpose detector, the PANDA spectrometer needs to ensure almost 4π coverage of the scattering solid angle, full and accurate multiple-particle event reconstruction and very good particle identification capabilities. % The electromagnetic calorimeter (EMC) will be a key item for many of these aspects. Particle energies ranging from some MeVs to several GeVs have to be measured with a relative resolution of 1% + 2%/√(E/ GeV). % It will be a homogeneous calorimeter made of PbWO₄ crystals and will be operated at -25 ^circle C, in order to improve the scintillation light yield. With the exception of the very forward section, the light will be detected by large area avalanche photodiodes. % The whole calorimeter has been designed in three sections: a forward end-cap, a central barrel and a backward end-cap (BWEC). % In this contribution, a status report on the development of the BWEC is given.

No abstract available

[en] The PANDA experiment wants to achieve a deeper understanding of the strong interaction. It is built at the new accelerator facility FAIR in Darmstadt. The electromagnetic process group in Mainz is developing the backward end-cap (BWEC) of the electromagnetic calorimeter. The prototype (PROTO16) serves for testing the final BWEC components for cooling, insulating, place consumption, photon read-out, electronics and signal transmission. PROTO16 got some major updates in the last year. The aim of these updates has been to improve the signal transmission for a better signal to noise ratio. New line driver boards have been developed. In the frame work of the signal enhancement, the latest version of the PANDA calorimeter preamplifier (APFEL-ASIC 1.5) has been introduced. Besides using geographical addressing, the key advantage is the individual biasing of the avalanche photodiodes. Furthermore, the slow control monitoring has been improved and detector stability has been enhanced. Two beam times with an 855 MeV electron beam at the Mainz Microtron Facility served for testing the improvements. This contribution discusses the results in terms of signal quality and detector stability.