Poster (POS)

The PANDA-Experiment will be a fixed target experiment at the future FAIR-accelerator center at Darmstadt, Germany. As the experiment is designed for high precision measurements with an antiproton beam, especially in the charm sector of hadron spectroscopy, a precise knowledge of the luminosity is crucial.

The determination of the luminosity will be done by measuring the angular distribution of elastically scattered antiprotons at very small scattering angles between 3 and 8 mrad. Therefore their tracks will measured by four layers of thinned HV-MAPS silicon sensors of 50μm thickness. To minimize the multiple scattering, the measurement is performed in vacuum. As the sensors will dissipate up to 7mW/mm^2, an active cooling is mandatory. To achieve this while maintaining a low material budget, the sensors will be glued on 200 μm thin CVD-diamonds which are clamped in an actively cooled aluminium heatsink outside of the acceptance. An excellent thermal contact to the stainless steel pipe for the coolant is ensured by melting the aluminium around the pipe before machining the heatsink. The poster will present the mechanical design and the cooling system.

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) near GSI, Darmstadt, Germany will address fundamental questions of hadron physics. Excellent particle identification is required to achieve the PANDA physics goals. Hadronic particle identification (PID) in the PANDA target spectrometer will be delivered by two DIRC (Detection of Internally Reflected Cherenkov light) counters. The Barrel DIRC will cover the polar angle range of 22−140 degree and is designed to provide pion/kaon separation for momenta between 0.5 GeV/c and 3.5 GeV/c with a separation power of at least 3 standard deviations. Several reconstruction algorithms have been developed to determine the performance of the detector. The "geometrical reconstruction" determines the Cherenkov angle relying primarily on the position of the detected photons. The "time imaging", however, utilizes both position and time measurements by directly performing the maximum likelihood fit. GEANT4 simulations and experimental data from prototype tests at the CERN PS were used to optimize the performance of the algorithms. We will discuss detailed aspects of both reconstruction approaches.

The electromagnetic target calorimeter (EMC) of the future $\overline{\text{P}}$ANDA detector has the challenging aim to detect high energy photons with excellent energy resolution from 15 GeV down to a few tens of MeV. To reach this goal, improved PbW0$_4$ scintillator crystals, cooled down to $-25^\circ \text{C}$ have been chosen. They provide a fast decay time for highest count rates, short radiation length for compactness, improved light yield for lowest thresholds and excellent radiation hardness. The target calorimeter itself is divided into a barrel and two endcaps. The individual crystal will be read out with two precisely matched large area avalanche photo sensors (APD). In the very inner part of the forward endcap, vacuum phototetrodes will be used instead. In this poster the construction and assembly status of the first slice of the barrel will be presented. This includes for example the assembly of detector subunits, mechanical support structure, the cooling system, optical monitoring system and front end electronics. This project is supported by the BMBF, GSI and HIC for FAIR.

An abstract for a poster presentation at the DPG Spring Meeting 2017 - Hadronic and Nuclear Physics and the poster itself.

The PANDA experiment will be one of the key projects of the new accelerator facility FAIR in Darmstadt. With its mature detector system it will be able to observe a variety of physical channels. Thus it will make a huge contribution to the understanding of the strong interaction. The electromagnetic process group (EMP) in Mainz is developing the backward end-cap (BWEC) of the electromagnetic calorimeter. For its construction various tests regarding mechanics have been carried out and are foreseen within the R&D framework. A full prototype of the moving supporting system was built and tested, comprising insertion rails and a movable trolley base. The rails were divided in two sections (fixed and removable in PANDA). A big change in the crystal support is being implemented as well and will be validated with a test setup, using FR4 as supporting material. In addition thermal studies using our current proto16 will be carried out.

The PANDA experiment at the Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD.
A fast focusing DIRC (Detection of Internally Reflected Cherenkov light) counter will provide hadronic particle identification (PID) in the barrel region of the PANDA detector.
To meet the PID requirements, the Barrel DIRC has to provide precise measurements of the Cherenkov angle, which is conserved for Cherenkov photons propagating through the radiator by total internal reflection.
The radiators, rectangular quartz bars, have to fulfill strict optical and mechanical requirements.
This includes the squareness and parallelism of the sides of the bars, sharp corners, and a very smooth surface polish, ensuring that the Cherenkov photons reach the optical sensors without angular distortions.
Two possible radiator shapes are being considered for the final detector design: either a conservative design with narrow bars or a cost-saving option using a wide plate
An optical setup, consisting of a computer-controlled positioning and multi-wavelength laser system, is used to evaluate the radiators to obtain critical values like transmittance and reflectivity.
The Setup, measuring procedure and results from radiator bar- and plate measurements will be presented on this poster.
Work supported by HGS-HIRe.

The high precision experiment PANDA is specifically designed to shed
new light on the structure and properties of hadrons. PANDA is a fixed
target antiproton proton experiment and will be part of Facility for
Antiproton and Ion Research (FAIR) in Darmstadt, Germany. When
measuring the total cross sections or determining the properties of
intermediate states very precisely e.g. via the energy scan method, the
precise determination of the luminosity is mandatory.
For this purpose, the PANDA luminosity detector will measure the
2D angular distribution of the elastically scattered antiproton trajectories.
For the determination of the luminosity the parametrization of
the differential cross section in dependence on the scattering angle is
fitted to the measured angular distribution. The fit function is highly
complex as it is not only able to corrected for the detection efficiency
and resolution, but also the antiproton beam shift, spotsize, tilt and
divergence. As most of these parameters are extracted from the fit,
this method is extremely powerful as it delivers also beam properties.
This poster will cover the complete luminosity determination procedure,
which is capable of extracting the luminosity with an accuracy
in the permille level.

An abstract for a poster presentation at the DPG Spring Meeting 2017 - Hadronic and Nuclear Physics

The PANDA detector [1] at the new, unique international accelerator facility FAIR, is designed to measure reactions induced by high intensity antiproton beams impinging on hydrogen as well as on nuclear targets, enabling a rich program of hadron physics in the charm quark sector. Hadronic particle identification in the region surrounding the interaction point will be performed with a Barrel DIRC, inspired by the successes of the BaBar DIRC [2]. The main task of the Barrel DIRC is to separate charged pions and kaons with > 3 for polar angles between 22 and 140 and particle momenta up to 3.5 GeV/c. In the baseline design long radiators (240 cm), surrounding the beam pipe at a radial distance of 47.6 cm, have on one end a highly reflective mirror and on the other end a lens system focussing the Cherenkov light into an expansion volume (EV). The EV directs the light from the radiator bars on to the photon detection plane. In test beams at GSI, pions with a momentum of 1.7 GeV/c hit the radiator coupled to a 30 cm-deep expansion prism, both made from synthetic fused silica, and with a 35 array of XP85012 [3] Microchannel-Plate PMTs (MCP-PMTs), comprising a total of 960 pixels, see Fig. 1.

The photon time of arrival and the time-over-threshold were measured by TDCs on a total of 24 trigger and readout boards (TRB3) [4]. An example of observed Cherenkov images is shown in Fig. 2. Further detailed studies were performed, in particular of wide radiator plates in combination with a variety of focusing optics, see Fig. 3, in a secondary hadron/lepton beam at the T9 beam line area of the CERN proton synchrotron. Wide plate radiators are of particular interest, due to significant fabrication cost reduction compared to narrow bars. The primary goal of the CERN beam test in 2015 was the experimental validation of the PID performance of the wide plate geometry using a time-based imaging reconstruction approach.

We present performance studies of the Barrel DIRC design for PANDA, based on test beam data at GSI and CERN, with the use of fast and finely segmented photon detectors, exploring the shape of radiator bars and lens systems to focus the Cherenkov photons. The results will form the basis for the Technical Design Report, expected to be completed by mid-2016.


References
[1] PANDA Collaboration, Physics Performance Report (arXiv:0903.3905v1), 2009.
[2] I. Adam, et al., Nucl. Instr. and Meth. A 538 (2005) 281.
[3] https://www.photonis.com/uploads/datasheet/pd/PLANACON-8x8-datasheet.pdf
[4] C. Ugur, et al., IEEE Nordic-MediterraneanWorkshop on Time to Digital Converters, 2013, DOI: 10.1109/NoMeTDC.2013.6658234.