Thesis

The
PANDA experiment is one of the main scientific pillars of the fu-
ture Facility for Antiproton and Ion Research, currently under construc-
tion in Darmstadt, Germany. It will investigate hadron physics measur-
ing antipron-proton annihilation reactions. The antiproton beam with mo-
menta between
1
.
5 GeV
/
c
to
15 GeV
/
c
, will allow to explore a broad physics
program including hyperon, open-charm and exotic hadronic states.
The Micro Vertex Detector (MVD) is the innermost sub-detector of the
tracking system of the
PANDA experiment. It is based on silicon sensors
with pixel and micro strip segmentation and its main task is the precise
spatial identification and measurement of primary and secondary decay
vertices.
This thesis describes the key features of the
PANDA Strip ASIC (PASTA),
a full-custom chip developed to read out the double-sided micro strip sen-
sors of the MVD. PASTA aims at highly resolved time-stamping and charge
information gathering through a time-digital approach. A Time to Digital
Converter (TDC), allowing a time bin width down to
50 ps
, measures the
Time over Threshold (ToT) of the sensor signals processed by a application
specific, newly developed front-end amplifier. In particular, this thesis re-
ports the theoretical studies yielding to the final implementation showing
the performance of the front-end stage evaluated with professional simula-
tion tools.

This thesis aims to study low-energy strong interaction effects of open-charm mesons. Our studies are based on the chiral Lagrangian supplemented by constraints from the heavy-quark spin symmetry. The pseudoscalar and vector open-charm-meson masses are calculated up to next-to-next-to-next leading order (N^3LO) corrections. Different assumptions on the counting rules are investigated. It is illustrated that a chiral expansion uniformly converges rapidly up to Goldstone boson masses as heavy as the kaon masses if formulated in terms of physical meson masses. First estimates of the relevant low-energy parameters are extracted from lattice QCD data on the quark mass dependence of the D meson masses. Such low-energy parameters are of crucial importance for the low-energy interaction of the Goldstone bosons with the D mesons.

To study rare processes, such as the formation of exotic particles, the PANDA experiment has been set up. To process the large dataflow, the subsystems preprocess the data. One example is the algorithm to search online for clusters in the data of the calorimeter, developed in this thesis. Due to the high interaction rates, the time is important. Optima have been determined to assign the data to (time)bunches (257, 97, and 15 ns) and hits to clusters (282, 122, and 40 ns), for interaction rates of 200 kHz and less, 2 MHz, and 20 MHz, respectively, and each hit must have a minimal energy of 3 MeV. Using these optima, the efficiencies for the investigated two- and seven-photon channels are 70-80% and 9-20%, respectively, depending on the interaction rate. In addition, it was investigated if the algorithm can run on the readout system, making use of the processing power in the data concentrators and the nodes in the data collection network. This was found to be possible, and, furthermore, the processing time using this approach is much lower. An important note to the efficiencies is that there were problems in creating the time stamps for the hits, which may cause the obtained results to deviate from reality. In addition, another step needs to be added to the reconstruction, where the event selection takes place, to determine the final efficiencies. It is recommended to proceed with the development of the cluster finding algorithm, as it delivers good performance at low costs.

Abstract
This thesis work, set in the framework of hadron physics, reports on a phenomenological and an experimental study dedicated to nucleon internal structure, both related to hadron electromagnetic form factor measurements in the time-like and in the space-like regions.
At the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, an experimental program aiming to determine the proton electromagnetic form factors in the time-like region is planned benefiting from the PANDA (anti-Proton Annihilation at Darmstadt) large acceptance detector through the annihilation reaction p̄p -> e+ e- and p̄p -> μ+ μ- in the energy range 2.25(1.5) ≤ √s(p L ) ≤ 5.47(15) GeV (GeV/c), where √s(p L ) is the total energy in the center of mass system (the beam momentum in laboratory frame). In such reactions, the difficulty will be to extract the signal of interest from the huge background coming from hadronic channels, mainly pion pair production. Phenomenological studies of meson pair production in p̄p annihilation is one of the subjects of this thesis. The goal is two-fold : to better evaluate the hadronic background and to improve our knowledge on the hadron internal structure as such reaction contains by itself useful information on the hadron quark content. For this purpose, an effective meson model has been developed to evaluate the cross section of p̄p annihilation into light meson pairs, taking into account mesonic and baryonic degrees of freedom, in the energy domain relevant to the PANDA experiment. A logarithmic form factor is introduced to account for the composite nature of the interacting hadrons. A comparison with the existing data for charged pion pair production and predictions for angular distributions and energy dependence are presented in the range 3.362(5) ≤ √s(p L ) ≤ 4.559(10.1) GeV (GeV/c). The model is applied to πp elastic scattering, using crossing symmetry, and to charged kaon pair production, on the basis of SU(3) symmetry. An exponential term is added to reproduce the energy dependence of the total cross section. The model is extended to different neutral channels π0π0, ηη, ηπ0 relying on SU(3) symmetry. The obtained angular distributions and energy dependences are presented and successfully compared to the existing data.
In the space-like region, the experimental effort, started years ago at Jefferson Laboratory (Newport News, VA, USA) and dedicated to precise measurements of the proton electromagnetic form factor ratio based on the recoil polarization method in elastic ep scattering, will be pursued up to higher momentum transfer squared, above 10 GeV2, and will be also applied to neutron. This method requires intense and highly polarized electron beams, as well as an accurate measurement of the polarization of the recoil particle, the proton or the neutron. In order to design and optimize the polarimetry in the GeV region, the determination of the efficiency and the analyzing powers, that combine into the figure of merit, is mandatory to conceive a polarimeter, as polarization experiments are very lengthy. In this context I contributed to the ALPOM2 experiment (JINR Dubna, Russia), the only experiment right now able to measure proton and neutron analyzing powers in the momentum range of interest for Jefferson Lab experiments and allowing considering different types of target. Experimentally, in the framework of ALPOM2, from the Nuclotron polarized deuteron beam (up to 13 GeV energy), polarized proton and neutron beams at 3.0, 3.75 and 4.2 GeV/c were obtained by deuteron break-up and the charged fragments from the collisions with C, CH2, CH and Cu targets were measured. For neutrons, in the beam momentum range from 1 to 6 GeV/c, two processes have been considered to determine the analyzing powers: np -> np (zero charge exchanged) and the charge exchange reaction np -> pn. From the comparison of the figures of merit associated to each of these two processes, the charge exchange reaction appears to be more efficient for polarimetry at high energy. Neutron analyzing powers for the charge exchange reaction on CH, and Cu targets have been measured up to 4.2 GeV/c for the first time. For the proton, more precise analyzing power data have been obtained. Experimental results of preliminary analysis are presented.

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.