Search

An overview of the various track finding methods for the barrel part of the PANDA detector will be presented. PANDA’s barrel tracking system consists of three detector parts. The innermost tracking detector is the Micro-Vertex-Detector (MVD). Surrounding the MVD is the the Straw Tube Tracker (STT), which consists of over 4200 drift tubes. Additionally, forward boosted tracks are identified by the Gas Electron Multiplier plates (GEM). The STT tubes produce coarse track information given by their tube ID and a drift time information which significantly improves the spatial resolution. The drift time information determines circles (isochrones) to which the tracks must pass tangentially.Track finding is divided into two parts: track finding for primary particles and for secondary particles. Two algorithms for each part are presented and compared. The two algorithms for primary particles are global tracking algorithms. The first algorithm is the current default track finder in PANDA and is based on adding hits to existing track assumptions. The second one is a track finder based on Hough transformations. For secondary particles a well optimized track finder based on a cellular automaton is compared to a novel approach that uses three chosen hits to find the true particle track.

Track reconstruction is essential for a meaningful physics analysis of data from complex detectors such as PANDA. For hyperon detection this task is even more challenging because hyperons typically several centimeters before they decay. Therefore, a secondary track finder for PANDA's barrel part will be presented. This algorithm, the ApolloniusTripletTrackFinder, is the only algorithm currently available at PANDA designed to find tracks not coming from the interaction point. Therefore, the finding rate for secondary particles is much higher (about 20 %-points) than for the currently existing algorithms. Combining this algorithm with a primary track finder promises to improve the reconstruction rate for hyperon decays. The performance of this algorithm for simple test cases and simulated physics processes will be presented.

Geneva : CERN Yellow Reports: Monographs 22MB (2021). doi:10.23731/CYRM-2021-003, Published by CERN Yellow Reports: Monographs, Geneva

The European physical journal / A 57(4), 138 (2021). doi:10.1140/epja/s10050-021-00388-w, Published by Springer, Heidelberg

Hades investigates nuclear matter and the properties of baryonic resonances. As part of the FAIR Phase-0 program, the hardware is being upgraded to enable a wide range of experiments, including investigating electromagnetic decays of hyperons produced in proton induced reactions. Feasibility studies show that the newly installed forward detectors are crucial for hyperon reconstruction. The hardware upgrade and feasibility studies in preparation for the February 2022 beamtime are presented.

In this work we study the performance of silicon photomultiplier (SiPM) light sensors after exposure to the JULIC cyclotron proton beam, of energy $\sim$ 39 MeV, relative to their performance before exposure. The SiPM devices used in this study show a significant change in their behavior and downward shift of their breakdown voltage by as much as $\sim$ 0.4$\pm$0.1 V. Single photon measurements appear to be no longer possible for the SiPMs under study after exposure to a dose of $\sim$ 0.2 Gy (corresponding to an integrated proton flux of $\sim$$\phi_{p}$=1.06x10$^{8}$ p/cm$^{2}$). No visible damage to the surface of the devices was caused by the exposure., Comment: 19 pages, 9 figures. arXiv admin note: text overlap with arXiv:1807.03007

The GENFIT toolkit, initially developed at the Technische Universitaet Muenchen, has been extended and modified to be more general and user-friendly. The new GENFIT, called GENFIT2, provides track representation, track-fitting algorithms and graphic visualization of tracks and detectors, and it can be used for any experiment that determines parameters of charged particle trajectories from spacial coordinate measurements. Based on general Kalman filter routines, it can perform extrapolations of track parameters and covariance matrices. It also provides interfaces to Millepede II for alignment purposes, and RAVE for the vertex finder. Results of an implementation of GENFIT2 in basf2 and PandaRoot software frameworks are presented here., 41 pages 24 figures, 1 table. Paper submitted to NIM

The matter formed in central heavy-ion collisions at a few GeV per nucleon is commonly understood as resonance matter, a gas of nucleons and excited baryon states with a substantial contribution from mesonic, mostly pionic excitations. Yet, in the initial phase of the reaction the system is compressed to beyond nuclear ground state density and hence substantial modifications of the hadron properties are expected to occur. The spectral distribution of virtual photons measured in Au+Au collisions at 2.4 GeV center of mass energy indicates strong medium effects beyond pure superposition of individual NN collisions. We present multi-differential distributions of low-mass electron pairs. This radiation is remarkably well described assuming emission from a thermalized system. To gain deeper understanding of the microscopic origin of the radiation, we extracted the centrality dependent true (not blue-shifted) temperature, its azimuthal distribution, as well as mass-dependent effective slope parameter. Virtual photon spectra are confronted with available model calculations.

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction View the MathML sourcedd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p -waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/cpd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pbσtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s-wave pion production.

Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation function for the $\it{pp\rightarrow pp\eta'}$ reaction close to threshold. Combining these data with previous results, we extract the scattering length for the $\it{\eta'}$-proton potential in free space to be $Re(a_{p\eta'}) = 0\pm0.43$ fm and $Im(a_{p\eta'})=0.37_{-0.16}^{+0.40}$ fm.

The presently world largest data sample of pi0 --> gamma e+e- decays containing nearly 5E5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi0 --> gamma U --> gamma e+e- decay from the pp-->pp\pi^0 reaction was carried out. An upper limit on the square of the U-gamma mixing strength parameter epsilon^2 of 5e-6 at 90% CL was obtained for the mass range 20 MeV, Comment: 16 pages, 8 figures; improved analysis extending the exclusion region to 20 MeV

One component of the future international Facility for Antiproton and Ion Research - FAIR is directed towards studies of hadronic matter at the sub-nuclear level with beams of antiprotons. These studies focus on two key aspects: confinement of quarks and the generation of the hadron masses. These goals will be pursued by performing precision measurements of charged and neutral decay products from antiproton-proton annihilation in the charmonium mass region. In this report an overview of the charmonium issues relevant to PANDA will be presented., Contribution to the proceedings of HQL06, Munich, October 16th-20th 2006

This year‘s annual report deviates from the usual IKP annual report because we want to exploit the effort entered into the preparation of the report for the POF evaluation. The report for the evaluation of the IKP activities within the project oriented funding of the Helmholtz association was one of the most important activities in 2017. The report covers nearly all achievements of 2017 and and thus it is highlighted in this annual report, and has been enhanced by including additional information. The highlights of 2017 include further achievements towards electric dipole measurements (JEDI), progress in the preparation of the PANDA detector and in the HESR component construction, results from COSY hadron physics experiments, strong increase of IKP contributions to neutrino physics experiments, a strong incresae in the CLAS analysis and preparation of phase-0 FAIR experiments at HADES. From the finished COSY experiments various scientific results have been produced, such as investigations of the properties of $\eta$ mesons at WASA, and continued analysis of data related to the d*(2380) resonance and the charge symmetry breaking reaction dd->$^{4}$He$\pi^{0}$. During the time before PANDA begins to produce data, the participation in the CLAS data taking and analysis at JLAB is ongoing and for the phase-0 experiments at FAIR a straw tube detector system for the HADES detector at GSI is being built. The preparations for FAIR are ongoing on the accelerator as well as on the experiment side. All dipoles for HESR were now tested and shipped to Darmstadt. The implementation of the HESR project is on time and in budget and also the developments for PANDA are progressing well. The activities towards electric dipole measurements achieved further steps in the aim of ultimate precision in polarization measurement and manipulation by controlling the spin precession rate and phase with a polarization feedback. The neutrino physics activities were extended with contributions to running (Borexino) and future (SOX, JUNO) experiments. Our activities within the different POF programs were very positively evaluated. The committee was impressed by the scientific program and realized that we deliver essential contributions for the various program topics. Our activities were considered as forefront, crucial and outstanding. This very good evaluation result is due to the work of all IKP colleagues during the last years. In spite of the unclear future of IKP the colleagues stayed highly motivated which was impressively demonstrated in the presentations for the POF review committee.

An important milestone has been reached in 2014: The evaluation of both the experimentaland the theoretical proposal for the third period of programme-oriented funding (PoF) of the Helmholtz Association resulted in excellent reports on the proposals presented by IKP. Consequently the base funding of the institute up to the end of 2019 has been secured. The institute thanks Prof. Dr. R. Maier for his strong scientific leadership of IKP-4 during the past thirty years, which has made a major contribution to the success of the IKP. He will continue to support the institute by his ideas and advice. We thank Prof. A. Lehrach for his fine interim management of IKP-4 after Prof. Maier’s retirement in early 2014. On December 1, IKP has welcomed the new director of IKP-4, Prof. Mei Bai.In the next five years, COSY will concentrate on two activities. In preparation of FAIR, COSY will test components of the high energy storage ring HESR and the detector system PANDA. Within the Jülich-Aachen research alliance (JARA), a precursorexperiment for the determination of the electromagnetic dipole moment (EDM) of charged particles in a storage ring will be developed by the JEDI collaboration. The experimental activities in hadron physics at COSY have ended in 2014. The program advisory committee (PAC) has completed its mission in 2014. The research center thanks both present and past members for their expert advice in choosing the most promising experiments. Beam time at COSY remains a precious commodity. The new COSY beam advisory committee (CBAC) will help to make the future COSY activities a success.

During the past year the Institute for Nuclear Physics (IKP) has faced a couple strategicwatersheds. Foremost of these is the upcoming retirement of Rudolf Maier, the head of theaccelerator institute (IKP-4), in early 2014. It is obvious that the accelerator group needsstrong scientific leadership given the tasks and commitments of IKP-4 — in particular in the context of building HESR at FAIR and of conceiving a possible future storage-ring project. Fortunately, the process of interviewing and subsequently hiring a successor to lead IKP-4 in the future is proceeding on track. Moreover, we have decided to phase out the hadron physics program at COSY. On the one hand this is motivated by the upcoming physics opportunities at HESR/PANDA, and on the other side by serious budgetary restrictions imposed on us. Consequently, we have readjusted our priorities as presented in the application for Programme-oriented Funding (PoF-3). Here about 70% of our resources (HESR; PANDA and PAX) are connected with FAIR, which according to a decision by the Helmholtz senate will not be evaluated. The remaining 30% are largely foreseen for the JEDI-project, which aims at a search for charged-particle electric-dipole moments in storage rings with unprecedented sensitivity. A smaller part will be used for research and development of accelerator components and advanced detector technologies. The corresponding PoF-applications for Matter and the Universe (MU) and Matterand Technology (MT), have been submitted and will be evaluated in the first quarter of 2014. In order to strengthen the cooperation between IKP and the physics department of the RWTH Aachen University in the field of basic research, a new section of the Jülich-Aachen Research Alliance (JARA) was founded last year and inaugurated in January 2013. Named JARA-FAME (Forces and Matter Experiments), its aim is to investigate the fate of antimatter (i) by searching for it with the Alpha Magnetic Spectrometer (AMS) on the International Space Station (ISS) and (ii) by investigating possible reasons for its disappearance, e.g., via the search for EDMs within JEDI. The technological highlight of 2013 was the installation and commissioning of the highenergy electron cooler in the COSY ring (see cover page). After delivery in December 2012 by the Budker Institute (Novosibirsk, Russia), it has been set up together with our Russian colleagues. In the meantime it has been tested at lower values of high voltage to prove that it works. As the next step we will study the device in detail with COSY beams and carefully increase the electron beam energy up to the maximum value of 2 MV duringthe upcoming year. Physics highlights of the past year comprise: [...]

A main focus of the Institut fuer Kernphysik (IKP) of Forschungszentrum Juelich (FZJ) is the design and construction of the High Energy Storage Ring (HESR) for the Facility for Antiproton and Ion Reseach (FAIR), which is being built at Helmholtzzentrum fuer Schwerionenforschung (GSI), Darmstadt. A corresponding contract between the FAIR company and FZJ has been signed in 2011 and 65 Me have been assigned for this purpose. An international consortium comprising IKP as the leading institution, the Zentralinstitut fuer Technologie (ZAT) of FZJ, the GSI, the Helmholtzinstitut Mainz (HIM) and the National Institute for R&D in Electrical Engineering (ICPE-CA), Bucharest, will build the HESR in the years up to 2018 and commission it afterwards. IKP is also contributing to the design and construction of the PANDA detector at HESR: after the decision of the PANDA collaboration to use a straw-tube tracker (STT) as the central tracking detector, a cooperation of IKP, Frascati, Pavia and Ferrara (Italy), Cracow (Poland) and Bucharest (Romania) will build the STT and later install it in PANDA. IKP is making essential contributions to the Micro-Vertex-Detector(MVD), as well as conceiving a day-one experiment for PANDA, and is involved in the PANDA pellet target development, together with IHEP (Moscow). In 2011 the Technical Design Reports have been finalized and approved by PANDA to be submitted to FAIR for these three detectors components (MVD, STT, target).

20 I 0 marks the first year of the second period of Program oriented Funding (PoF), the new scheme of providing resources within the Helmholtz Association of German Research Centers. In October a further milestone for the FAIR project was accomplished by signatures of the international agreement on its construction and the subsequent foundation of the FAIR GmbH. The Institut für Kernphysik (IKP) of Forschungszentrtum Jülich (FZJ) is heavily involved in FAIR as the consortiumleader for the construction ofthe High Energy Storage Ring (HESR) and a major contributor to the PANDA detector. In addition IKP is working on a method to produce beams of polarized antiprotons by spin filtering for a possible future FAIRIHESR-upgrade. In October, a Program Advisory Council, chaired by Stephan Paul (TU Munich), was held at IKP to advise IKP and FZJ management on the future plans and strategy of the institute. Besides the IKP program outlined for PoF-2 for COSY and FAIR, the committee strongly endorsed the PAX spin filtering project and the plans to investigate the possibilities of a search for an electric dipole moment (EDM) of proton and/or deuteron ($^{3}$He) at storage rings, which could lead to a future IKP facility. lt also recommended to renew the position of the IKP-4 director (R. Maier) after his retirement in 2014 as early as possible. The followillg experimental and theoretical highlights are worth mentioning: • The decay of the eta into two charged pions and a photon has been measured by the WASA-at-COSY collaboration. • Analyzing powers and cross sections for the reaction $\vec{p}$n $\rightarrow$ (pp)$_{s}$$\pi$$^{-}$ have been obtained at ANKE for a beam energy T$_{p}$ = 353 MeV. The results are in agreement with, but extend, existing data in literature. They allow one to determine the low-energyconstant d in the 4N$\pi$ constant interaction of Chiral Perturbation Theory with very small systematic errors. • The WASA collaboration has obtained new data on two-pion production in the proton-proton reaction at the invariant collision energy $\sqrt{s}$s = 2.46 GeV. The data are not compatible with a conventional double Delta excitation. The COSY-TOF collaboration took data on the reaction $\vec{p}$p $\rightarrow$ pKA and extracted the Kaon analysing power, completing a first step in the determination of the spin triplet proton-Lambda scattering length. • The strong-interaction parameters in pionic deuterium have been measured with unprecedented precision. • Theory has derived the pion-deuteron scattering length from a consistent treatment of both strong and electromagnetic few body effects. The systematic uncertainties of the pion nucleon coupling constant are now controlled, reslilting in g$^{2}_{c}$/4$\pi$ = 13.7 ± 0.2 (see cover).[...]

The IKP has achieved a strategic success in 2009: the proposal of the IKP for funding in the Research Program Physics of Hadrons and Nuclei, defined in the framework of the Program Oriented Funding of the Helmholtz centers, has been evaluated in February with great success. This decision guarantees the funding of IKP as well as those parts of ZAT and ZEL participating in the proposal for the time period from 2010 till 2014. The following outstanding experimental results have been obtained: • The WASA at COSY collaboration has used the pd $\rightarrow$ $^{3}$He $\eta$ reaction to accumulate 30 million $\eta$-meson decays, obtaining clear signatures of 300 events of the type $\eta$ $\rightarrow$ $\pi^{+}\pi^{-}e^{+}e^{-}$ These data are relevant for tests of the chiral anomaly.

On July 1, the board of directors of the Forschungszentrum Jülich (FZJ) founded the$\textbf{Jülich Center for Hadron Physics (JCHP)}$. The main goal of the JCHP is to coordinatethe hadron physics activities at the FZJ for the FAIR project. This includes activitiesat the Institute for Advanced Simulations (IAS), the Institut für Kernphysik (IKP), theZentralinstitut für Elektronik (ZEL) and the Zentralabteilung Technologie (ZAT). Withinthe Helrnholtz Association (HGF) research field $\textit{Structure of Matter}$, the FZJ operatesthe COSY facility and has achieved an excellent international reputation due to the closecooperation between accelerator physicists, experimentalists and theoreticians. In cooperationwith ZEL and ZAT, the IKP is in charge of the construction and operation of theHigh Energy Storage Ring HESR and makes a strong contribution to the PANDA detectorand its physics. PAX is exploiting methods to effectively polarize (anti-)protons for apossible future upgrade at FAIR.The FZJ operates the JUGENE/JSC supercomputer and hosts the John von Neumann institutewhich develops lattice gauge simulation calculations of quantum chromodynamics(QCD) and hadron structure. The JCHP coordinates these activities by establishing a directconnection between the lattice QCD simulation groups and hadron physicists. Moreover,the infrastructure provided by the IAS for mass storage, presently used for COSYdata, may handle FAIR data and perform Monte Carlo simulations of HESR experiments.External users are essential for the success of an accelerator complex, therefore, the JCHPfacilitates the contact of external users with the FZJ and supports external activities in thefield of hadron physics. Presently an initiative of the universities within North-RhineWestfalia and the FZJ, called NRW-FAIR, is forming to coordinate their FAIR-relatedactivities.Starting December 1, 2008, the IKP-3 theorists also work in IAS-4, the strong interactionphysics branch of the Institute for Advanced Simulations (IAS). The Virtual Institute $\textit{Spinand Strang QCD}$ has presented its first results on June 1 in Ferrara.A Helmholtz-Russia Joint Research Group, the first one in Jülich, will receive fundingfrom the Impuls- und Vernetzungsfond of the Helmholtz Association and from the RussianFoundation for Basic Research for the next three years. In a joint effort of the FZJ,the Budker Institute in Novosibirsk, TU Dortmund and JINR Dubna methods for electroncooling in the MeV region, relevant for FAIR, will be developed.The IKP has initiated a cooperation with the 100-TW laser facility at the HeinrichHeineUniversity Düsseldorf. The potential of new particle acceleration technologies withlimited-mass targets will be explored, exploiting the know-how on frozen-pellet targetsgained at the IKP. The year 2008 has seen important experimental and theoretical progress: [...]