Talk

Hyperons serve as powerful probes for investigating various aspects of quantum chromodynamics (QCD). As part of the FAIR Phase-0 program, the HADES (High-Acceptance Di-Electron Spectrometer) at GSI collected high-statistics proton-proton data using a proton beam with a kinetic energy of 4.5 GeV. The beam energy enables the production of hyperons close to threshold, facilitating studies of hyperon-hyperon interactions and searches for intermediate resonances. Currently, the ΛΛ reaction is being analyzed to extract crucial information on hyperon interactions, which is expected to be essential to understand the interiors of neutron stars. Furthermore, the first-time measurements of the Dalitz decay of the Σ0 will provide insights into transition form factors and thereby the electromagnetic structure of the Σ0. The study of Ξ- production in proton-proton collisions is valuable to address the observed excess yields observed in Ar+KCl and p+Nb reactions at HADES. This talk will highlight the ongoing hyperon physics analyses at HADES within the FAIR Phase-0 program and present selected results.

The abundant production of hyperons in antiproton-proton annihilations open new avenues in the investigations of strong interactions and fundamental symmetries. In recent years, the BESIII experiment has demonstrated the merits of studying spin polarised and correlated hyperon-antihyperon pairs with several pioneering measurements of hyperon structure and precise tests of CP conservation.
With a beam of stored antiprotons, the PANDA experiment can take hyperon physics to a new level, benefitting from the expected huge samples of hyperon-antihyperon pairs. In this talk, I will discuss the potential of hyperon physics with PANDA in particular but also with antiproton beams in general.

PANDA is one of the main experiments at the FAIR facility at GSI which will study different aspects in QCD by, e.g., performing hadron spectroscopy, among others in searching for glueballs and exotic states, and by investigating hyperons. The PANDA experiment will use an antiproton beam in the momentum range of 1.5 to 15 GeV/c colliding with a stationary target. Due to antiproton-proton annihilations the production of exotic particles and states is directly possible. The PANDA detector consists of a target and forward spectrometer. Two DIRC detectors, a cylindrically shaped Barrel DIRC (BaD) around the interaction region and an Endcap Disc DIRC (EDD) covering the forward hemisphere, will be used for particle identification in particular for π/K separation up to 4 GeV/c.
Since the focal planes of both DIRC detectors will reside in an ∼ 1 T magnetic field and because of other boundary conditions microchannel-plate photomultipliers (MCP-PMTs) are the only viable sensor candidates. Their advantageous properties in terms of excellent time resolution, moderate dark count rate and especially their favorable gain behavior inside magnetic fields make them most suitable for the PANDA DIRCs. During a planned PANDA operation time of ∼10 years at full luminosity the MCP-PMTs have to withstand >5 C/cm2 integrated anode charge without any QE losses. Previous aging problems of MCP-PMTs were recently solved by applying the ALD (atomic layer deposition) coating technique. For this matter an ultrathin layer of alumina or magnesia covers the MCP glass substrate leading to an increased MCP-PMT lifetime of up to a factor ∼100. The current status of these measurements will be presented. Furthermore the sensors have to be capable to detect single photons at very high rates [∼0.2 MHz/cm2 (BaD) and up to 1 MHz/cm2 (EDD)].
To measure these and other performance parameters by surface scans a semi-automatic setup was built, consisting of a light tight and copper shielded box combined with a 3-axis stepper and a picosecond laser pulser. With the multihit capable, FPGA-based DiRICH/TRB (Trigger and readout Board) DAQ many parameters like time resolution, dark count rate, afterpulsing ratio, charge sharing crosstalk and electron recoil behavior, but also QE and gain homogeneity, can be simultaneously obtained as a function of the xy-position. This paper will present new insights to the performance parameters of several types of the very latest multi-anode MCP-PMTs. In particular properties like gain and internal parameters like charge cloud width and electron recoil distributions were investigated also inside the magnetic field. In addition the performance of new MCP-PMTs from Photonis with an anode layout of 3 ×100 pixels will be shown in this talk. Also recently observed side effects with the latest two ALD layer MCP-PMTs will be reviewed.

The PANDA experiment will investigate proton-antiproton colli-sions with the utmost precision at the antiproton storage ring HESR at FAIR. It aims to address fundamental questions of QCD, i.e., mainly the theory of strong interaction and hadron physics [1,2]. The antiprotons with a beam momentum of up to 15 GeV/c will interact with protons delivered by a cluster-jet target. Due to the 4π detector surrounding the interaction point the cluster source and beam dump each need to be located in a distance of more than 2 m to the interac-tion point connected by a narrow jet beam pipe. For the success of this experiment it is indispensable to achieve world record target thicknesses in such large distances to the nozzle and develop a new state-of-the-art cluster-jet target.
A first prototype cluster-jet target was set up in Münster. Here, first investigations on beam properties were performed and the design tar-get thickness of 4.5×1015 atoms/cm² at the later interaction point in more than 2 m distance to the nozzle was reached [3]. Based on the obtained insights into cluster-jets and setup handling, the final Münster Cluster-Jet Target was designed which is topic of this presentation.
Within the cluster-jet target, hydrogen is cooled down to tempera-tures ranging from 20 to 40 K and pressed with 5 to 20 bar through a convergent-divergent Laval nozzle expanding into a first vacuum chamber (fig. 1). The resulting cluster-jet is separated from the gas background by a skimmer and afterwards tailored by a collimator, each optimizing the vacuum conditions. After a transition vacuum chamber, the cluster-jet is injected into the accelerator vacuum. With movable skimmer and collimator and a nozzle tilting system, the jet can be aligned within its beam pipe, crossing the interaction point after 2.25 m and entering the beam dump after in total nearly 5 m.
Three differentially pumped beam dump stages are separated by ad-justable orifices allowing to minimize the gas backflow (fig. 2).
Within the first stage an absolute thickness monitor system is in-stalled. Two orthogonal rods are moved one after another stepwise through the cluster-jet. Impinging clusters lead to a pressure increase proportional to the density of the cluster-jet. Furthermore, an MCP can be moved into the cluster-jet allowing for an online vertex zone visualization. In combination with an electron gun a total illumina-tion of the cluster-jet is possible which is a useful tool in aligning the cluster-jet through its narrow beam pipe and is a further way of determining the cluster-jet density. Additionally, by pulsing the electron gun the MCP system can be used for a precise velocity measurement of single clusters, which is needed for the thickness determination.
This state-of-the-art cluster-jet target setup and the implemented innovative beam diagnostic tools are topic of this presentation.

Presentation of the build & deployment mechanisms forseen for the DCS software system within PANDA at the Build and Deployment Workshop at the EPICS Collaboration Meeting.

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The ToASt ASIC is a 64 channel integrated circuit designed for the readout
of the Silicon Strips that will equip the Micro-Vertex Detector of the PANDA
experiment.
The ToASt ASIC is synchronous to a 160 MHz clock, which defines also the
time resolution. A common time stamp is distributed to all channels to
provide a common time reference for time of arrival and time over threshold
measurements. Two 160 Mb/s serial lines provide the interface to the data
concentrator.
ToASt is implemented in a commercial 110 nm CMOS technology with triplicated
logic to protect against single event upsets.

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), Darmstadt, Germany, will address fundamental questions of hadron physics using $\bar{p}p$ annihilations. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID in the target region will be provided by a Barrel DIRC (Detection of Internally Reflected Cherenkov light) counter.
The Barrel DIRC, covering the polar angle range of 22-140 degrees, will provide a $\pi$/K separation power of at least 3 standard deviations (s.d.) for charged particle momenta up to 3.5 GeV/c. The design of the Barrel DIRC features narrow radiator bars made from synthetic fused silica, an innovative multi-layer spherical lens focusing system, a prism-shaped synthetic fused silica expansion volume, and an array of lifetime-enhanced Microchannel Plate PMTs (MCP-PMTs) to detect the hit location and arrival time of the Cherenkov photons. Detailed Monte-Carlo simulations were performed, and reconstruction methods were developed to study the performance of the system. All critical aspects of the design and the performance were validated with system prototypes in a mixed hadron beam at CERN. In 2020 the PANDA Barrel DIRC project advanced from the design stage to component fabrication. The series production of the fused silica bars was completed in 2021 and the first MCP-PMTs were delivered in 2022.
We will discuss the validation of the technical design using prototypes and present results from the quality assurance measurements for the bars and MCP-PMTs.