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

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

Has the neutral double hypernucleus ∧∧4n{}_{\wedge}^{}{}_{\wedge}^4\rm{n} been observed?

The BNL-AGS E906 experiment was the first fully electronic experiment to produce and study double hypernuclei with large statistics. Unfortunately, the interpretation of the measured $\pi^{−}−\pi^{−}$ momentum correlation is still blurry because the hypothesized production of ${}_{\Lambda }^{3}\rm{H}{+}_{\Lambda }^{4}\rm{H}$ pairs remains questionable. We show, that neither a scenario where the hypernuclei are produced after the capture of a stopped $\Xi^-$ by a $^9$Be nucleus nor interactions of energetic $\Xi^-$ with $^9$Be nuclei in the target material can produce a sufficient amount of such pairs. We have therefore explored the conjecture that decays of the $_{\Lambda}^{~}{}_{\Lambda}^4\rm{n}$ may be responsible for the observed structure. Indeed, the inclusion of $_{\Lambda}^{~}{}_{\Lambda}^4\rm{n}$ with a two-body $\pi^-$ branching ratio of 50% in the statistical multifragmentation model allows to describe the E906 data remarkably well

Has the neutral double hypernucleus nΛΛ4 been observed?

The BNL-AGS E906 experiment was the first fully electronic experiment to produce and study double hypernuclei with large statistics. Two dominant structures were observed in the correlated π−–π− momentum matrix at (pπ−H,pπ−L)=(133,114)MeV/c and at (114,104)MeV/c. In this work we argue that the interpretation of the structure at (133,114)MeV/c in terms of Λ3H+Λ4H pairs is questionable. We show, that neither a scenario where these single-Λ hypernuclei are produced after capture of a stopped Ξ− by a 9Be nucleus nor interactions of energetic Ξ− with 9Be nuclei in the target material can produce a sufficient amount of such twin pairs. We have therefore explored the conjecture of Avraham Gal that decays of the Image 1 may be responsible for the observed structure. Indeed, the inclusion of Image 1 with a two-body π− branching ratio of 50% in a statistical multifragmentation model allows to describe the E906 data remarkably well. On the other hand, a bound Λ3n nucleus would cause a striking structure in the momentum correlation matrix which is clearly inconsistent with the observation of E906. Keywords: Hypernuclei, Statistical decay mode

Status of J-PARC E07: Systematic study of double strangeness nuclei with hybrid emulsion method

© 2019 Author(s). J-PARC E07 is the most complex emulsion experiment to date investigating double hypernuclei with a hybrid emulsion method. This experiment aims to detect 104 Ξ- stop events, ten times more events than the past experiments. Thus, an unequivocal identification of several new double hypernuclei is expected. The beam exposure has been completed at the K1.8 beam line of the J-PARC hadron facility in June 2017. The photographic development of all emulsion sheets has also been completed in February 2018. The emulsion sheets are presently being analyzed with dedicated optical microscopes. Current statistics is comparable to that of E373 and so far 10 events of 3-vertices topology have been detected. A typical event of double Λ hypernucleus and a twin Λ hypernucleus are introduced. We plan to complete the main part of the emulsion scanning within a year