DPG (DPG)

Das PANDA-Experiment, welches im Antiproton-Speicherring HESR an der im Bau befindlichen
Beschleunigeranlage FAIR in Darmstadt stehen wird, ist für Fragen der Hadronenphysik optimiert.
Mit dieser Anlage wird es möglich sein, neue Zustände zu entdecken und die Linienform dieser wie
auch bereits bekannter Zustände sehr präzise zu vermessen. Zur Normierung der dafür verwendeten
Energie-Scan-Messungen wird die exakte Kenntnis der Luminosität benötigt.
Die Luminosität wird bei PANDA anhand der Winkelverteilung der elastischen Antiproton-Proton-Streuung
bestimmt. Um eine absolute Messgenauigkeit von 5% zu erreichen werden die Spuren der gestreuten
Antiprotonen gemessen. Dazu werden 4 Detektorebenen mit gedünnten Siliziumsensoren verwendet
(HV-MAPS). HV-MAPS sind Pixelsensoren mit integrierter Ausleseelektronik. Sie werden mit einer
Sperrspannung von 60 V betrieben, um die Strahlenhärte zu erhöhen. Die 4 Ebenen, die verfahrbar
montiert sind, bestehen aus CVD-Diamanten auf denen die Sensoren aufgeklebt sind. Zur Reduktion
der Vielfachstreuung wird der Aufbau im Vakuum betrieben.
Das Konzept des Luminositätsdetektors wird vorgestellt und dabei technische Aspekte wie Vakuumsystem,
Kühlung und Elektronik diskutiert, sowie Einblicke in die Datenanlyse gegeben.

The PANDA experiment at FAIR (Facility for Antiproton and Ion Re-
search in Europe) at GSI, Darmstadt, will study fundamental questions
of hadron physics and QCD. A compact, fast focusing Ring Imaging
Cherenkov counter using the DIRC (Detection of Internally Reflected
Cherenkov light) technology, will provide charged particle identifica-
tion (PID) in the barrel region of the PANDA experiment. To meet
the PANDA PID requirements, the Barrel DIRC has to provide pre-
cise measurements of the Cherenkov angle, which is conserved for
Cherenkov photons propagating through the radiator by total internal
reflection. The radiators, rectangular bars made from synthetic fused
silica, have to fulfill strict optical and mechanical requirements. This
includes squareness and parallelism of the bar sides, sharp corners,
and smoothly polished surfaces in the order of 10 Å, ensuring very lit-
tle angular distortions and high transport efficiency. An optical setup,
consisting of a computer-controlled positioning and multi-wavelength
laser system, is used to evaluate the bars to obtain critical values like
transmittance and reflectivity. Prototypes from various manufacturers
using different production techniques have been tested to qualify ven-
dors for the Barrel DIRC bar production. Setup, measuring procedure
and measurement results will be presented in this contribution.

Testing of silicon strip detectors with a spatially resolved infrared laser test-stand*
— ∙Martin Kesselkaul, Kai-Thomas Brinkmann, Tommaso Quagli, Robert Schnell, and Hans-Georg Zaunick for the PANDA-Collaboration
— II. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, D-35392 Gießen

The PANDA experiment at the future accelerator facility FAIR will investigate proton-antiproton reactions at a stationary target. The Micro Vertex Detector (MVD), as the innermost detector of PANDA, will measure the tracks of charged particles and secondary decay vertices close to the interaction point with high precision. It is comprised of various layers of silicon-pixel and -strip sensors.
For the characterization and quality measurement of the double-sided silicon strip detectors used in the PANDA MVD, a laser test-stand has been developed. An automated xy-table with an position accuracy of 50 nm places an infrared laser above the sensor while recording the spatially resolved response of the sensor. This contribution will focus on the analysis of the data taken with this setup. The quantities of interest are the charge collection efficiency (CCE), as well as the charge sharing characteristics between adjacent strips, which are inferred for analysis of the sensor quality. The latter will be discussed in detail for different measurement parameters to deduce the spatial resolution of the sensor.
*Funded by BMBF and HIC for FAIR

Um sicherzustellen, dass die Hochspannungsjustiereinheit der im Elektromagnetischen Kalorimeter des PANDA Experimentes am zukünftigen FAIR Komplex in Darmstadt verwendeten Avalanche Photodioden (APD) während der Betriebsdauer funktionsfähig bleibt, wurden Untersuchungen zur Strahlenhärte durchgeführt. Die Veränderungen der Justierelektronik wurde anhand der Kennlinienveränderungen (Dunkelstrom bei anliegender Spannung) ausgewählter APDs bestimmt, welche als Referenz dienten. Unterschiedliche bestückte Platinen des Prototyps der Justiereinheit wurden am Strahlenzentrum in Gießen sowohl Neutronen als auch Gammastrahlung ausgesetzt. Zusätzlich wurde eine Platine am AGOR am KVI-CART/Groningen (Niederlande) mit Protonen bestrahlt. Die verwendete Gammastrahlendosis übersteigt die erwartete Strahlendosis hinter den im Kalorimeter verwendeten Bleiwolframat-Kristallen um ein Vielfaches. Die Anzahl der Hadronen (∫φ dt) lag bei den Tests unterhalb der im Experiment erwarteten. Zusätzlich wurde untersucht, ob Veränderungen der Elektronik anhand einer aufgenommenen Kennlinie vor der Bestrahlung und einer entsprechenden Kennlinie nach der Bestrahlung zurückgerechnet werden können. Die Ergebnisse dieser Untersuchungen des Prototyps der Hochspannungsunterversorgung des PANDA EMCs sollen vorgestellt werden. *gefördert durch das BMBF und HIC for FAIR

The PANDA experiment at the new FAIR facility will use two DIRC detectors for hadron identification. The focal plane of both DIRC detectors will be located inside a magnetic field of ∼1 T. In the PANDA environment the only sensor option for the detection of the Cherenkov photons are Microchannel-Plate Photomultipliers (MCP-PMTs). The most limiting parameter until a few years ago was the lifetime of the MCP-PMTs. The quantum efficiency (QE) correlated to the integrated anode charge (IAC) being measured in the sensor is an indicator for the lifetime. The QE will decrease with increasing IAC because of aging processes taking place at the photo cathode (PC) until the sensor is "blind". One of these processes is the interaction of feedback ions from the residual gas which may damage the PC on impact. The Erlangen lifetime setup is capable of illuminating various MCP-PMTs simultaneously and monitoring their IAC. The spectral QE of the sensors is measured every few weeks and full surface scans are made every few months. This talk will present the current setup and the latest obtained results. The focus will be on recent 2-inch MCP-PMTs from Photonis and Hamamatsu. IACs of ≫5 C/cm2 were obtained with no or only minor QE loss which is sufficient for both PANDA DIRCs.

The PANDA experiment at the new FAIR facility at GSI in Darmstadt will investigate open questions of hadron physics in the momentum region of 1.5−15 GeV/c with pp annihilations. The excellent particle identification (PID) needed will be achieved by two DIRC detectors. The Barrel DIRC will surround the interaction point and perform a π/K separation for momenta of 0.5−3.5 GeV/c at polar angles from 22∘ to 140∘. Its design is based on the successful BaBar DIRC with several improvements to make it more compact and to achieve a separation power larger than 3 σ for the expected momentum region of the π/K. In the forward region of the detector the Endcap Disc DIRC will be located to cover an angular region from 5∘ to 22∘ and clearly separate π/K up to 4 GeV/c with a separation power of about 3 σ. For the detection of the Cherenkov photons lifetime-enhanced MCP-PMTs will be used in combination with fast readout electronics. The radiators will be made of precisely polished fused silica to guarantee a low photon loss ratio and conserve the Cherenkov angle during their propagation through the optical components using internal total reflection. To evaluate the designs Geant4 simulations and tests of different prototypes have been performed at various beam facilities. This talk will present both detector concepts and the achieved results.

Presenting the PANDA Disc DIRC prototype used in the DESY 2016 test beam time and reporting on the test beam results.

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 $\bar{p}p \rightarrow l^{+}l^{-}$ (l = e, $\mu$) 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.