The PANDA experiment at FAIR offers unique possibilities for performing hyperon physics.
The detector will enable the reconstruction of both hyperon and antihyperon, which will
be created together in proton-antiproton collisions. This enables investigations of the strong
interaction in the non-perturbative regime. Due to their relatively long-lived nature, the hyperons
impose a particular challenge on the track reconstruction and event building. In order to
exploit the large expected reaction rates to the fullest, PANDA will utilize a fully software-based
event filtering. Therefore, reconstructing hyperons for such a filter requires online track
reconstruction that can handle particles created a measurable distance away from the interaction
point and, at the same time, operate on free streaming data is needed. Until antiprotons are
available at PANDA, a part of the hyperon program can be carried out with the predecessor,
PANDA@HADES using a proton beam.
In this thesis, investigations of the detector signatures from the decay channels Λ → pπ-, Ξ- →
Λπ- and Ω- → Λ K- produced in YbarY reactions are presented. The detector signatures guide
the subsequent track reconstruction algorithms. A candidate for online track reconstruction
algorithms on free streaming data based on a 4D Cellular Automaton has been developed and is
benchmarked. It utilizes information from the PANDA straw tube tracker and is agnostic to the
point of origin of the particle. The track reconstruction quality assurance procedure and results
from the tracking at different event rates are also presented. Finally, extrapolation algorithms
for including hit information from additional detectors in the tracks are outlined.
In order to maximize the potential of the predecessor experiment PANDA@HADES, a
kinematic fitting procedure has been developed for HADES that combines geometric the decay
vertex information of neutral particles and track parameters such as momentum. Benchmark
studies on simulated data from the channel p(3.5 GeV)p → ΛK+p are presented as well as tests
of the kinematic fit on experimental data from 2007.
Next-generation DIRC detectors, like the PANDA Barrel DIRC, with improved optical designs and better spatial and timing resolution, require correspondingly advanced reconstruction and PID methods. The investigation of the PID performance of two DIRC counters and the evaluation of the reconstruction and PID algorithms form the core of this thesis. Several reconstruction and PID approaches were developed, optimized, and tested using hadronic beam particles, experimental physics events, and Geant simulations. The near-final design of the PANDA Barrel DIRC was evaluated with a prototype in the T9 beamline at CERN in 2018. The analysis finds excellent agreement between the experimental data and the Geant simulations for all reconstruction algorithms. The best PID performance of up to $5.2 \pm 0.2$ s.d. $\pi$/K separation at 3.5 GeV/c, was obtained with a time imaging PID method. The PANDA Barrel DIRC simulation, as well as the reconstruction and PID algorithms, were evaluated using experimental data from the GlueX DIRC as part of the FAIR Phase-0 program. The performance validation was carried out using physics events of the GlueX experiment and simulations. The initial analysis results of the commissioning dataset show a $\pi$/K separation power of up to 3 s.d. at a momentum of 3.0-3.5 GeV/c, obtained using a geometric reconstruction algorithm.
The Barrel Time-of-Flight Detector (B-ToF) is a timing detector for the Panda
experiment which is currently under construction at the Facility for Antiproton and
Ion Research (FAIR) in Darmstadt, Germany. In fixed target p̄p collisions, with
antiprotons accelerated up to a momentum of 15 GeV/c producing a center of mass
energy of up to 5.5 GeV, open questions of hadron physics will be studied. This
effort includes charmonium spectroscopy and the search for exotics and hybrids
as well as the study of hypernuclei and of hadrons in matter. In this context the
B-ToF complements the particle identification information of the DIRC detectors
and provides valuable information for particles in the lower momentum range up
to about 1 GeV/c via relative time-of-flight measurements.
A >1800 mm long transmission line PCB connects the SiPMs on the scintillators
to the front-end electronics and provides mechanical support to the scintillator tiles
acts as the backbone of the detector. In order to determine the best performing
layout three prototype iterations are examined and tested for the crosstalk level and
signal attenuation effects. While the crosstalk is negligible in all design iterations
an amplitude reduction of (11.7 ± 0.5) % is observed for the newest board prototype
using low loss materials. This is well above the attenuation of a standard coaxial
cable. The employed connections lead to a doubling of the signal rise time. The
effect of this on the time resolution is yet to be determined.
To achieve intended functionality a highly granular and efficient detector design
is necessary providing a time resolution of below 100 ps. The detector is made up
of 16 identical sections each carrying 120 scintillating tiles, which are read out by
an array of four SiPMs connected in series.
This work presents time resolution scans using a 90 Sr source over the entire
scintillator surface in order to evaluate the detector performance and determine the
optimal scintillator tile thickness. Comparing four 3 mm to 6 mm thick scintillator
tiles, the measurements show that a 5 mm thick scintillator providing a mean
time resolution of 52.3 ps with a spread of ±5.9 ps over the entire surface, is the
optimal choice for the detector. In addition the performance was verified in test
beam measurements at the T9 beamline at CERN under conditions closer to the
expected conditions in Panda using mixed particle beam mainly containing pions
and kaons. Time resolutions of (55.8 ± 4.3) ps to (80.1 ± 1.5) ps were measured for
detector modules utilizing SiPMs by different manufacturers.
The topic of the following thesis is the investigation of Microchannel-Plate Photomultiplier Tubes (MCP-PMTs) and their suitability for the P̄ANDA experiment. After an introduction to the physical goals of P̄ANDA the setup of the detector will be described. The Cherenkov detectors for particle identification, for which the MCP-PMTs are used, will be discussed in more detail. After this the general functionality and new improvements of the MCP-PMTs will be illustrated. The different measurement methods for the performance parameters will be explained in detail. The results obtained in this thesis show that at least two MCP-PMTs that have been optimized in a long R&D process, the Hamamatsu R13266-07-M64M and the PHOTONIS XP85112/A1-Q-HA, are well suited for the usage in P̄ANDA.
The main focus of this thesis is the investigation of the aging and the measurement of the lifetime of newly developed MCP-PMTs. A critical value for the lifetime is the quantum efficiency, which is measured as a function of the integrated anode charge. An existing lifetime measurement setup has been modified during this work to fit the measurement requirements of the new MCP-PMTs. The lifetime increases significantly when a so-called ALD coating is applied to the MCP pores. This caused the lifetime measurements to get lengthy. With the results of this thesis it can be concluded that this new treatment method leads to an increased lifetime by a factor of 50 − 100 compared to not treated devices. The obtained results are also in agreement with the few measurements obtained at other institutions. Furthermore, it could be shown, that the aging of the photocathode is caused by feedback ions. These ions get accelerated by the electrical field of the PMT and damage the photocathode irreversibly on impact. The ALD coating reduces this flux of feedback ions considerably. Meanwhile, MCP-PMTs are the favored sensors for high energy experiments, which expect a high radiation environment and need a very fast single photon detection that is located in a high magnetic field.
Submitted by l.capozza on Thu, 06/08/2020 - 14:04.
In recent decades, the quantum field theory of strong interaction (QCD) has been impressively demonstrated in the area of high energies and momentum transfers. Nowadays, novel experiments allow for challenging the methods for the calculation of QCD also in the non-perturbative regime by the continuous improvement of measurement accuracy. PANDA at the upcoming FAIR accelerator facility is one of such experiments. At PANDA, antiprotons with momenta of up to15 GeV/c will be annihilated at a fixed proton target under high luminosities. Among a variety of detector systems, PANDA stands out with its lead tungstate electromagnetic calorimeter (EMC), which is designed to have a wide dynamic range (10 MeVto14.6 GeV) and a relative energy resolution of better than 2.5 % at 1 GeV. The development of the backward part of the PANDA EMC is the first scientific goal of this thesis. Since the development of the backward EMC has progressed so far, it is foreseen for an experiment within the FAIRPhase-0 research programme. It is proposed to measure the double-virtual electromagnetic transition form factor (TFF) of the pion in the Primakoff π0 electroproduction at the Mainz Microtron facility (MAMI). The pion TFF is related via the hadronic light-by-light scattering to the g_μ−2 puzzle. Consequently, the second scientific goal of this thesis are preparatory studies for FAIR Phase-0. The developments of this work resulted in a fully functional prototype calorimeter, which operated stably in numerous tests at MAMI. However, the focus of this work is digital signal processing (DSP) for the PANDA EMC. A specially developed software framework allowed for testing and optimising signal filtering algorithms and parameter extraction methods on realistically simulated signals. Thus, the algorithms are well-adapted to the time structure of the ̄PANDA calorimeter preamplifier (APFEL) signals. Furthermore, the DSP methods were implemented on the Field Programmable Gate Arrays (FPGAs) of the PANDA digitisation board. The developed FPGA firmware provides a self-triggering readout for all calorimeter channels, an efficient implementation of a high order filter with a finite impulse response (FIR), noise hit suppression and pileup handling.Together with the calorimeter prototype, the digital signal processing was tested at MAMI. Thanks to the use of the DSP methods, an energy detection threshold (single-crystal) of less than 2.5 MeV was achieved. This allowed for a measured relative energy resolution of 2.190(2) % at 1 GeV. Moreover, the non-linearity of the calorimeter is in the order of a few per mill. Due to the self-triggering concept of the FPGA firmware,measurements under high detector rates were possible. Thus, a dead time of 464(13) ns and a pileup probability of 4.53(12) % at 100 kHz was determined. For the measurement of the pion TFF, a high flux of low energy electrons and photons is expected. Thus, test beams with the prototype were performed to determine the impact of the low energetic background on the measurement. By utilising both experiment data and simulations, an upper limit for the relative energy resolution (2.75(4) % to 6.57(2) % at 1 GeV) as a function of the luminosity (2.77μb−1/s to 55.34μb−1/s) was found. The study allows an estimation of the FAIR Phase-0 measuring time.