1. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Patrick Achenbach U Mainz Sept. 2o13

2. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Theoretical calculations Cluster model, shell model, mean field … Hypernuclear spectroscopy Unique laboratory to investigate the YN interaction Nuclear force Large base of NN scattering data Nuclear Structure Normal / exotic nuclei Hyperon force Limited YN/YY scattering data Nuclear Structure Hypernuclei Baryon interaction

3. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz The A = 4 isospin doublet The A = 4 isospin doublet  Nucleon-hyperon interaction can be studied by strange mirror pairs  Coulomb corrections are < 50 keV for the 4 Λ H - 4 Λ He pair  Energy differences of strange mirror pair are much larger than for 3 H - 3 He pair With precise spectroscopy details of NY-interaction inferred

4. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz The A = 7 isospin triplet Assumed CSB potential may be too naïve Further study on A = 4 hypernuclear systems necessary [E. Hiyma, NPA 914, 130 (2013).] 7 Li(e,e’K + ) 7 Λ He [N. Nakamura et al., PRL 110, 12502 (2013).] 7 Be Λ (T=1) 7 Li Λ 7 He Λ 5.36 (without CSB) (with CSB)

5. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Hypernuclear production methods two regimes for hypernuclear and hyperfragment production:  bound hypernuclear states  highly excited quasi-free region hypernucleus quasi-free  [O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys. 57, 564 (2006).] [From J-Lab Hall-A]

6. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Hypernuclear decay-pion spectroscopy p e’ e 9 Be 9  Li * K+K+ 7 Li -- d 7  He fragmentation two-body decay  mono-energetic pions

7. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Examples of   spectroscopy KEK-E287, E326 beam: stopped K - target: thick 7 Li 7 Λ Li 11 Λ B FINUDA Coll. and A. Gal, Phys Rev. B 681 (2009) 139 A. Gal, Nucl. Phys. A 828 (2009) 72 intense and high quality primary electron beam (R > 10 14 Hz,  < 100  m) + thin target (~10 mg/cm 2 ) decay π - spectroscopy with high resolution and high accuracy Severe limitations by statistics or momentum resolution

8. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Goals of decay pion spectroscopy Masses with high accuracy for light hypernuclei: 3  H, 4  H, …, 11  B, 12  B Determination of charge symmetry breaking (CSB) effects: ( 4  H ↔ 4  He), ( 6  He ↔ 6  Li), ( 7  He ↔ 7  Li * ↔ 7  Be), … Search for hypernuclei near the neutron drip line: 6  H, 7  H, 8  H … important information for  coupling [cf Hiyama] 6  H: the “superheavy hyper-hydrogen – puzzle” [cf Fukuda and Feliciello] pion momentum resolution ~ 100 keV/c → mass resolution ~100 keV/c 2 (FWMH) → accuracy of a few 10 keV/c 2

9. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Decay-pion spectroscopy at MAMI

10. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Accessible hypernuclei missing mass sepctroscopy

11. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz TOF system tracking system Cherenkov system Particle detection system in K AOS time-of-flight reso- lution with TOF walls FWHM = 400 ps pion detection ε > 95% by aerogel Cherenkov

12. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Kaon identification using TOF system protons pions kaons pions kaons protons low / high momentum setting K AOS can cover 200 – 1300 MeV/c in only 2 settings clean kaon identification by TOF at low momenta Cherenkov information used for high momenta low / high momentum setting

13. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Pioneering experiment 2o11 K AOS can be operated at zero-degree scattering angle PID suffers from high positron background positrons hadrons

14. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Dedicated experiment 2o12

15. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Decay pion detection Decay pions from strange hadrons (K,π) (K,μ) (K,e) (K,π) (K,μ) (K,e)

16. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Signal interpretation

17. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz Examples of decay-pion spectra To minimize human bias two independent analyses performed: Final spectra to be released by end of year

18. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz ConclusionsConclusions -Two current questions in few-body physics: -Decay pion spectroscopy gives access to ground-state masses of hypernuclei and could answer the questions! -At MAMI pioneering experiments were followed by an experiment with a dedicated setup: Clean tag on strangeness production at zero-degree Clean pion sample from weak decays of hyperons retrieved Current analysis limited by statistics → continuation with luminosity increase by one order of magnitude planned How can we understand the A = 4 and A = 7 hypernuclei? Is the superheavy hyper-hydrogen nucleus bound?

19. Recent Studies of Hypernuclei Formation with Electron Beams at MAMI Sept. 2o13 P Achenbach, U Mainz A1 Hypernuclear Collaboration