Detector software

PANDA Management Quarterly Report 18Q3

Proceedings for the CHEP 2018. Deadline for initial submission is October 31st, 2018.

One of the main topics of interest in physics is the composition and structure of matter. Especially for hadrons, which are bound states of quarks and gluons such as the proton and neutron, the description is incomplete. Quantumchromodynamics (QCD), the theory of the strong interaction, is in accordance with most of the results from measurements. However QCD as well as derived effective theories or lattice-QCD calculations are unable to fully explain the rich hadron spectrum. The isoscalar part of the hadron spectrum is particularly interesting, because states with a large gluon content are expected in this sector. In order to validate or invalidate theories, the precise measurement of the states is crucial. The mass and width of states can be measured by energy scans. With the method of partial wave analysis one is able to extract additional information such as the spin and parity of the states. In this respect, the BESIII experiment at IHEP in Beijing and the future PANDA experiment at FAIR in Darmstadt, will contribute with valuable information.

A key parameter for such experiments is the luminosity, which is needed for energy scans and the measurement of absolute cross sections. In this thesis the implementation of the versatile LuminosityFit software package is presented. It is responsible for the determination of the luminosity from the reconstructed tracks of the PANDA luminosity detector with high stability and an accuracy of below 0.5 %. Essential for the small systematic uncertainty is the correction of influences from the accelerator beam and the target. In consequence a high accuracy for line shape measurements of resonances is ensured with the highly accurate luminosity determination.

Furthermore this thesis aims towards the extraction of the isoscalar mesons in the reaction J/ψ → π⁰π⁰γ. The presence of many wide and interfering states makes a correct theoretical description difficult. To address this matter the implementation of the helicity formalism for the general partial wave analysis framework ComPWA is presented in this thesis. The goal of ComPWA is to establish the comparability of various theoretical models and formulations. The study of the isoscalar mesons can benefit from the direct comparison of different theories. This implementation of the helicity formalism takes the novel approach by using an expert system. An exhaustive validation of the implementation is performed on the basis of the J/ψ → π⁰π⁰γ reaction. With the availability of the helicity formalism in ComPWA, partial wave analysis can be performed with this first general model, that serves as a reference for comparisons with other implementations.

The Endcap Disc DIRC has been developed to provide an excellent particle identification
for the future PANDA experiment by separating pions and kaons up to a momentum of 4 GeV/c with
a separation power of 3 standard deviations in the polar angle region from 5 ◦ to 22 ◦ . This goal will
be achieved using dedicated particle identification algorithms based on likelihood methods and will
be applied in an offline analysis and online event filtering. This paper evaluates the resulting PID
performance using Monte-Carlo simulations to study basic single track PID as well as the analysis
of complex physics channels. The online reconstruction algorithm has been tested with a Virtex4
FGPA card and optimized regarding the resulting constraints.

The Endcap Disc DIRC (EDD) has been developed to provide an excellent particle identification in the future PANDA experiment by separating pions and kaons up to a momentum of 4\,GeV/c with a separation power of 3\,s.d.. The detector is placed in the forward endcap of the PANDA target spectrometer. It consists of a fused silica plate and focusing elements placed at the outer rim, which focus the Cherenkov light on the photo cathodes of the attached MCP-PMTs. A compact and fast readout of the signals is realized with special ASICs. The performance has been studied and validated with different prototype setups in various testbeam facilities.

The PANDA detector at the future FAIR facility at GSI is planned as a fixed- target experiment for proton-antiproton collisions at momenta between 1.5 and 15 GeV/c. It will be used to address open questions in hadronic physics. In order to achieve a sufficient particle identification, two different DIRC detector concepts have been developed. This talk will cover the Endcap Disc DIRC detector which is placed at the forward endcap of the PANDA target spectrometer and will provide a 3σ separation of pions and kaons up to a momentum of 4 GeV/c for polar angles from 5° to 22°. The most important component of the DIRC detector is a 2 cm thin fused silica radiator plate that is divided into 4 identical quadrants. The surfaces are polished with high precision in order to guarantee little photon losses by total reflection and conserve the Cherenkov angle during propagation through the optical system. Intrinsic chromatic errors will be minimized by the implementation of an optical filter. The readout system consists of 96 readout elements with focusing optics and attached MCP-PMTs to focus the photons that are produced by the Cherenkov cone of the traversing particle and acquire their position and timing information. This new detector concept requires the development of dedicated reconstruction and particle identification algorithms which permit an efficient analysis of the measured time-correlated photon patterns. Time and event based simulations with dedicated Monte-Carlo simulation frameworks have been used to validate the PID requirements of the DIRC counter. Additionally, the Monte-Carlo simulations have been used to estimate the radiation dose in different detector volumes in order to compare these values with actual measurement results.

Beim PANDA-Experiment können Hadronen aller Quantenzahlen erzeugt werden, in-
dem Antiprotonen auf ein Target innerhalb des PANDA-Detektors geschossen werden.
Schwerpunkte der Forschung sind die starke Wechselwirkung, die Spektroskopie von D-,
D s -Mesonen und Charmonium, sowie die Erforschung von Hadronen mit gluonischer An-
regung und Glueballs. Alle Messdaten des Detektors werden kontinuierlich erfasst und in
Echtzeit nach physikalisch interessanten Werten durchsucht (online event filtering). Um
die Datenmenge von bis zu 200 GBit/s zu verarbeiten, ist ein umfangreiches Computer-
netzwerk erforderlich.
Ein solches Netzwerk, das zahlreichen Nutzern zur Verfügung steht und teilweise mit
dem Internet verbunden ist, birgt immer auch die Gefahr der Manipulation. Die vorlie-
gende Arbeit widmet sich der Frage, wie sich die Übertragungswege der Messdaten des
PANDA-Experiments schützen lassen. Es wird beschrieben, wie das Protokoll TLS und
verschiedene Verschlüsselungs- bzw. Signaturalgorithmen den Schutzbedarf des PANDA-
Experiments erfüllen. Da es in der Vergangenheit jedoch mit Hilfe zeitbasierter Seiten-
kanalangriffe gelungen ist, die Sicherheitsfunktionen von TLS zu überwinden, wird die
Messgenauigkeit von Antwortzeiten in einem Computernetzwerk unter Optimalbedin-
gungen und darüber hinaus in realitätsnahen Szenarien untersucht.