Hypernuclear Physics at PANDA

Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Anti-proton and Ion Research FAIR at Darmstadt, Germany. A copious production of Xi-hyperons at a dedicated internal target in the stored anti-proton beam is expected, which will enable the high-precision gamma-spectroscopy of double strange systems for the first time. In addition to the general purpose PANDA setup, the hypernuclear experiments require an active secondary target of silicon layers and absorber material as well as high purity germanium (HPGe) crystals as gamma-detectors. The design of the setup and the development of these detectors is progressing: a first HPGe crystal with a new electromechanical cooling system was prepared and the properties of a silicon strip detector as a prototype to be used in the secondary target were studied. Simultaneously to the hardware projects, detailed Monte Carlo simulations were performed to predict the yield of particle stable hypernuclei. With the help of the Monte Carlo a procedure for Lambda-Lambda-hypernuclei identification by the detection and correlation of the weak decay pions was developed.Comment: prepared for the International Conference on Exotic Atoms and Related Topics (EXA2011), Vienna, Sept. 5-9, 201

Many Facets of Strangeness Nuclear Physics with Stored Antiprotons

Stored antiprotons beams in the GeV range represent a unparalleled factory for hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of strange hadronic systems with unprecedented precision. The behavior of hyperons and -- for the first time -- of antihyperons in nuclear systems can be studied under well controlled conditions. The exclusive production of $\Lambda\bar{\Lambda}$ and $\Sigma^-\bar{\Lambda}$ pairs in antiproton-nucleus interactions probe the neutron and proton distribution in the nuclear periphery and will help to sample the neutron skin. For the first time, high resolution $\gamma$-spectroscopy of doubly strange nuclei will be performed, thus complementing measurements of ground state decays of double hypernuclei with mesons beams at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange $\Xi$-atoms are feasible and even the production of $\Omega^-$-atoms will be within reach. The latter might open the door to the $|s|$=3 world in strangeness nuclear physics, by the study of the hadronic $\Omega^-$-nucleus interaction and the very first measurement of a spectroscopic quadrupole moment of a baryon which will be a benchmark test for our understanding of hadron structure.Comment: Proceddings of HYP201

Comparison of seven prognostic tools to identify low-risk pulmonary embolism in patients aged <50 years

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Hypernuclear physics studies of the P̅ANDA experiment at FAIR

Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Antiproton and Ion Research FAIR at Darmstadt (Germany). [1, 2] Thanks to the use of stored p̅ beams, copious production of double Λ hypernuclei is expected at the PANDA experiment, which will enable high precision γ spectroscopy of such nuclei for the first time, and consequently a unique chance to explore the hyperon-hyperon interaction. In particular, ambiguities of past experiments in determining the strength of the ΛΛ interaction will be avoided thanks to the excellent energy precision of a few keV (FWHM) achieved by germanium detectors. Such a resolution capability is particularly needed to resolve the small energy spacing of the order of (10–100) keV, which is characteristic from the spin doublet in hypernuclei the so –called “hypernuclear fine structure”. In comparison to previous experiments, PANDA will benefit from a novel technique to assign the various observable γ-transitions in a unique way to specific double hypernuclei by exploring various light targets. Nevertheless, the ability to carry out unique assignments requires a devoted hypernuclear detector setup. This consists of a primary nuclear target for the production of Ξ− + Ξ¯$\overline \Xi$ pairs, a secondary active target for the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform γ spectroscopy. Moreover, one of the most challenging issues of this project is the fact that all detector systems need to operate in the presence of a high magnetic field and a large hadronic background. Accordingly, the need of an innovative detector concept will require dramatic improvements to fulfil these conditions and that will likely lead to a new generation of detectors. In the present work details concerning the current status of the activities related to the detector developments for this challenging programme will be given. Among these improvements is the new concept for a cooling system for the germanium detector based on a electro-mechanical device. In the present work, the cooling efficiency of such devices has been successfully tested, showing their capability to reach liquid nitrogen temperatures and therefore the possibility to use them as a good alternative to the standard liquid nitrogen dewars. Furthermore, since the momentum resolution of low momentum particles is crucial for the unique identification of hypernuclei, an analysis procedure for improving the momentum resolution in few layer silicon based trackers is presented

Hypernuclear physics studies of the P̅ANDA experiment at FAIR

Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Antiproton and Ion Research FAIR at Darmstadt (Germany). [1, 2] Thanks to the use of stored p̅ beams, copious production of double Λ hypernuclei is expected at the PANDA experiment, which will enable high precision γ spectroscopy of such nuclei for the first time, and consequently a unique chance to explore the hyperon-hyperon interaction. In particular, ambiguities of past experiments in determining the strength of the ΛΛ interaction will be avoided thanks to the excellent energy precision of a few keV (FWHM) achieved by germanium detectors. Such a resolution capability is particularly needed to resolve the small energy spacing of the order of (10–100) keV, which is characteristic from the spin doublet in hypernuclei the so –called “hypernuclear fine structure”. In comparison to previous experiments, PANDA will benefit from a novel technique to assign the various observable γ-transitions in a unique way to specific double hypernuclei by exploring various light targets. Nevertheless, the ability to carry out unique assignments requires a devoted hypernuclear detector setup. This consists of a primary nuclear target for the production of Ξ− + Ξ¯$\overline \Xi$ pairs, a secondary active target for the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform γ spectroscopy. Moreover, one of the most challenging issues of this project is the fact that all detector systems need to operate in the presence of a high magnetic field and a large hadronic background. Accordingly, the need of an innovative detector concept will require dramatic improvements to fulfil these conditions and that will likely lead to a new generation of detectors. In the present work details concerning the current status of the activities related to the detector developments for this challenging programme will be given. Among these improvements is the new concept for a cooling system for the germanium detector based on a electro-mechanical device. In the present work, the cooling efficiency of such devices has been successfully tested, showing their capability to reach liquid nitrogen temperatures and therefore the possibility to use them as a good alternative to the standard liquid nitrogen dewars. Furthermore, since the momentum resolution of low momentum particles is crucial for the unique identification of hypernuclei, an analysis procedure for improving the momentum resolution in few layer silicon based trackers is presented

Feasibility study of performing high precision gamma spectroscopy of lambda lambda hypernuclei in the PANDA experiment

Hypernuclear physics is currently attracting renewed interest, due tornthe important role of hypernuclei spectroscopy rn(hyperon-hyperon and hyperon-nucleon interactions) rnas a unique toolrnto describe the baryon-baryon interactions in a unified way and to rnunderstand the origin of their short-range.rnrnHypernuclear research will be one of the main topics addressed by the {sc PANDA} experimentrnat the planned Facility for Antiproton and Ion Research {sc FAIR}.rnThanks to the use of stored $overline{p}$ beams, copiousrnproduction of double $Lambda$ hypernuclei is expected at thern{sc PANDA} experiment, which will enable high precision $gamma$rnspectroscopy of such nuclei for the first time.rnAt {sc PANDA} excited states of $Xi^-$ hypernuclei will be usedrnas a basis for the formation of double $Lambda$ hypernuclei.rnFor their detection, a devoted hypernuclear detector setup is planned. This setup consists ofrna primary nuclear target for the production of $Xi^{-}+overline{Xi}$ pairs, a secondary active targetrnfor the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform $gamma$ spectroscopy.rnrnIn the present work, the feasibility of performing high precision $gamma$rnspectroscopy of double $Lambda$ hypernuclei at the {sc PANDA} experiment has been studiedrnby means of a Monte Carlo simulation. For this issue, the designing and simulation of the devoted detector setup as well as of the mechanism to produce double $Lambda$ hypernuclei have been optimizedrntogether with the performance of the whole system. rnIn addition, the production yields of double hypernuclei in excitedrnparticle stable states have been evaluated within a statistical decay model.rnrnA strategy for the unique assignment of various newly observed $gamma$-transitions rnto specific double hypernuclei has been successfully implemented by combining the predicted energy spectra rnof each target with the measurement of two pion momenta from the subsequent weak decays of a double hypernucleus.rn% Indeed, based on these Monte Carlo simulation, the analysis of the statistical decay of $^{13}_{Lambda{}Lambda}$B has been performed. rn% As result, three $gamma$-transitions associated to the double hypernuclei $^{11}_{Lambda{}Lambda}$Bern% and to the single hyperfragments $^{4}_{Lambda}$H and $^{9}_{Lambda}$Be, have been well identified.rnrnFor the background handling a method based on time measurement has also been implemented.rnHowever, the percentage of tagged events related to the production of $Xi^{-}+overline{Xi}$ pairs, variesrnbetween 20% and 30% of the total number of produced events of this type. As a consequence, further considerations have to be made to increase the tagging efficiency by a factor of 2.rnrnThe contribution of the background reactions to the radiation damage on the germanium detectorsrnhas also been studied within the simulation. Additionally, a test to check the degradation of the energyrnresolution of the germanium detectors in the presence of a magnetic field has also been performed.rnNo significant degradation of the energy resolution or in the electronics was observed. A correlationrnbetween rise time and the pulse shape has been used to correct the measured energy. rnrnBased on the present results, one can say that the performance of $gamma$ spectroscopy of double $Lambda$ hypernuclei at the {sc PANDA} experiment seems feasible.rnA further improvement of the statistics is needed for the background rejection studies. Moreover, a more realistic layout of the hypernuclear detectors has been suggested using the results of these studies to accomplish a better balance between the physical and the technical requirements.rnDie Hyperkernphysik erfreut sich derzeit wieder einer erh{"o}htenrnAufmerksamkeit, denn die Spektroskopie von Hyperkernen ist ein wichtigesrnHilfsmittel, um die Baryon-Baryon-Wechselwirkung in einheitlichter Weise zurnbeschreiben und den Ursprung ihrer kurzen Reichweite zurnverstehen.\ Hyperkernforschung ist eines der Hauptthemen, mit dem sich dasrnPANDA-Experiment an der geplanten Anlage f{"u}r Antiproton- undrnIonenforschung FAIR befassen wird. Durch die Nutzung des gespeichertenrnAntiproton-Strahls wird eine ergiebige Erzeugung vonrnDoppelt-$Lambda$-Hyperkernen erwartet, welche erstmalig diern$gamma$-Spektroskopie solcher Kerne mit hoher Pr{"a}zision erm{"o}glichenrnwird. Bei PANDA sollen angeregte Zust{"a}nde von $Xi^-$-Hyperkernen dazurnbenutzt werden, Doppelt-$Lambda$-Hyperkerne zu erzeugen. F{"u}r derenrnNachweis ist ein eigener Detektoraufbau vorgesehen. Dieser besteht aus einemrnprim{"a}ren Kerntarget f{"u}r die Erzeugung vonrn$Xi^-$+$overline{Xi}$-Paaren, einem sekund{"a}ren aktiven Target f{"u}rrndie Hyperkernbildung und dem Nachweis der damit verbundenen Zerfallsprodukternsowie einem Array aus Germaniumdetektoren zur $gamma$-Spektroskopie.\ In derrnhier vorliegenden Arbeit wurde die Machbarkeit einer hochpr{"a}zisenrn$gamma$-Spektro-skopie von Doppelt-$Lambda$-Hyperkernen im PANDA-Experimentrnunter Verwendung von Monte-Carlo-Simulationen untersucht. Hierf{"u}r wurdenrnAufbau und Simulation des Detektorsystems sowie der Mechanismus der Erzeugungrnvon Doppelt-$Lambda$-Hyperkernen optimiert. %, %ebenso die physikalische %Ergiebigkeit des Gesamtsystems.rnZus{"a}tzlich wurde die Ausbeute der Doppelt-Hyperkern-Produktion in stabilenrnangeregten Zust{"a}nden mit einem statistischen Zerfallsmodellrnuntersucht.\ Eine Strategie f{"u}r die eindeutige Zuordnung der vielen neurnzu beobachtenden $gamma$-{"U}ber-g{"a}nge zu spezifischenrnDoppelt-Hyperkernen wurde erfolgreich implementiert, indem die vorhergesagtenrnEnergie-Spektren eines jeden Targets mit der Messung der zwei Pion-Impulse ausrndem nachfolgenden schwachen Zerfalls der Doppelt-Hyperkerne kombiniertrnwurden.\ Eine Methode zur Behandlung des Untergrunds basierend aufrnZeit-Messungen wurde ebenfalls implementiert. Jedoch liegt der Anteil derrnmarkierten Ereignisse, die im Zusammenhang mit der Erzeugung vonrn$Xi^-$+$overline{Xi}$-Paaren stehen, nur zwischen 20% und 30%. Daherrnwurden weitere {"U}berlegungen angestellt, um diesen Wert um einen Faktorrnzwei zu erh{"o}hen. Der Beitrag der Untergrundreaktionen zu denrnStrahlensch{"a}den an den Germanium-Detektoren wurde ebenfalls in derrnSimulation untersucht. Zus{"a}tzlich wurde ein Test durchgef{"u}hrt, um diernVerminderung der Energieaufl{"o}sung der Germanium-Detektoren bei Anwesenheitrnvon Magnetfeldern zu {"u}berpr{"u}fen. Es wurden keine signifikantenrnVerschlechterungen der Energieaufl{"o}sung oder in der Elektronikrnbeobachtet. Eine Korrelation zwischen der Anstiegszeit und der Pulsform wirdrnbenutzt, um die gemessene Energie zu korrigieren.\ Alles in allem erscheintrndie Durchf{"u}hrung der $gamma$-Spektroskopie vonrnDoppelt-$Lambda$-Hyper-kernen im PANDA-Experiment m{"o}glich. Eine weiterernVerbesserung in der Statistik wird f{"u}r die Untersuchung derrnUntergrund-Unterdr{"u}ckung ben{"o}tigt. Dar{"u}berhinaus wurde einrnrealit{"a}tsn{"a}herer Aufbau des Hyperkern-Detektors vor-geschlagen, welcherrndie Ergebnisse der hier vorgestellten Untersuchungen nutzt, um ein besseresrnGleichgewicht zwischen physikalischen und technischen Anforderungen zurnerreichen

Production of excited double hypernuclei via Fermi breakup of excited strange systems

Precise spectroscopy of multi-strange hypernuclei provides a unique chance to explore the hyperon-hyperon interaction. In the present work we explore the production of excited states in double hypernuclei following the micro-canonical break-up of an initially excited double hypernucleus which is created by the absorption and conversion of a stopped $\Xi^{-}$ hyperon. Rather independent on the spectrum of possible excited states in the produced double hypernuclei the formation of excited states dominates in our model. For different initial target nuclei which absorb the $\Xi^-$, different double hypernuclei nuclei dominate. Thus the ability to assign the various observable $\gamma$-transitions in a unique way to a specific double hypernuclei by exploring various light targets as proposed by the {\Panda} collaboration seems possible. We also confront our predictions with the correlated pion spectra measured by the E906 collaboration.Comment: accepted in Physics Letters