Hypernuclear Spectroscopy with Electron Beams Patrick Achenbach (U Mainz) for the E05-115 Collaboration at JLab for the A1 Collaboration at MAMI 27 Jan 2o11

Production of hypernuclei [CERN (1959-1978)] secondary kaon- or pion beams [SKS (1991-2001 and 2011+)] n p L

Production of hypernuclei [HKS (2005-2009)] electron beams [Kaos (2008+)] available electron machines: CEBAF at Jefferson Lab MAMI-C in Mainz

strangeness production Cross sections [O. Hashimoto, H. Tamura, Prog. in Part. and Nucl. Phys. 57 (2006) 564] small momentum transfer  ΔL~0 and ΔS=0 strangeness exchange large momentum transfer ΔL ≠ 0 ΔS ≠0 for (e,e´K+) strangeness production MAMI-C magic momentum

Quantitative comparison to meson production methods The goals of the hypernuclear programme with electron beams are: the detection of unknown (core-excited) hypernuclear states the measurement of kaon angular distributions precise determination of binding energies experimental requirements: mass resolution δM <1 MeV/c² large kaon angle acceptance [O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys. 57, 564 (2006).]

Detection of hypernuclei Detection issues cross-sections of mb for (π,K) and (K,π), but only of μb for (e,e’K) limited spectrometer acceptances Ω « 4π  kaon count rate in the kaon arm small  compensate with high beam intensity > 10 μA vs. ~100/sec for (K,π)  very small coincidence rates compared to background rates  rate limitations of detectors  K/π separation crucial experimental requirements: dedicated spectrometers and beamlines necessary

HKS/HES installation at JLab Hall C Aug–Nov 2009 @ JLab Hall-C Targets: 7Li, 9Be, 10B, 12C, 52Cr magnetic chichane S. N. Nakamura O. Hashimoto

Kaos installation at MAMI-C available 2011 @ MAMI-C Targets: lH, 7Li, 9Be, 12C, … B A C kaonarm 2nd arm beam KAOS

First approach: Missing mass spectroscopy Mx-ML [MeV/c2] L S0 E05-115 (2009) preliminary Kaos (2009) preliminary

Strategies for spectroscopy of light -hypernuclei Kinematic issues strong Q2–dependence:  electron detection at forward angles: Θlab< 10o Kaos: Θ ~ 1o JLab: Θ ~ 6o

Strategies for spectroscopy of light -hypernuclei Kinematic issues strong angular dependence:  kaon detection at forward angles: ΘK < 10o Kaos: Θ ~ -12-8o JLab: Θ ~ 1-13o

Hypernuclear isotopes detected at JLab

Hypernuclear spectra obtained at JLab (< 2oo9) [F. Dohrmann et al., Phys. Rev. Lett. 93, 242501 (2004). L. Yuan et al., Phys. Rev. C 73, 044607 (2006). J. J. LeRose et al., Nucl. Phys. A 804, 116 (2008). F. Cusanno et al., arXiv:0810.3853 [nucl-ex]. O. Hashimoto, Proc. Int. Conf. Hypernuclear and Strange Particles 2006 (HYP06), pp. 41-46, Springer 2007.]

12C(e,e’K+)12LB, 12C(p+,K+)12LC reference spectrum with best resolution

28Si(e,e’K+)28LAl, 28Si(p+,K+)28LSi #1 #2 #3 first d-shell hypernuclear spectroscopy by (e,e’K+)

7Li(e,e’K+)7LHe First reliable observation of 7ΛHe with good statistics [M. Juric et al. Nucl. Phys. B 52 (1973) 1] [prepared by O. Hashimoto]

Binding energies in the A=7 hypernuclear system Comparison of binding energies now getting sensitive to CSB [prepared by O. Hashimoto]

Charge symmetry breaking in ΛN interaction Emulsion [prepared by O. Hashimoto]

Second approach: decay pion spectroscopy 9Be 9Li* K+ Jefferson Lab Proposal: Realization unclear! Spokespersons: Liguang Tang, L. Yuan, S.N. Nakamura, et al. MAMI: Experiment in 2011! in Kooperation mit O. Hashimoto, S. N. Nakamura, L. Tang et al. d 7He 7Li - Fragmentation (<10-16s)

Decay-pion spectroscopy setup at MAMI for 2011 kaon arm decay-pion arm pre-target beam chicane beam 1500 MeV beam energy Be and Li targets zero-degree kaon tagging by Kaos high resolution decay-pion spectroscopy

Hypernuclei from a 9Be target Two-body decays of 12 different hypernuclei Breakup Mode Q value (MeV) - Decay P (MeV/c) Width (keV/c) FWHM 9Li - 9Be + - 121.18 165 p + 8He -13.817 8Li + - 116.40 n + 8Li -3.756 8Be + - 124.12 2p + 7H -40.328 (B=6.1) 7He + - 135.17 ~270 d + 7He -12.568 7Li + - 114.61 2n + 7Li -12.218 7Be + - 108.02 3He + 6H -29.608 (B=5.1) 6He + - 133.47 3H + 6He -9.745 6Li + - 108.39 3n + 6Li -18.957 6Be + - 100.58 ~220  + 5H -11.749 (B=4.1) 5He + - 133.42 ~900 n +  + 4H -12.005 4He + - 132.95 6He + 3H -18.183 3He + - 114.29 [from Liguang Tang]

Summary With a high quality electron beam from CEBAF (e,e’K) hypernuclear spectroscopy was established The 2nd generation experiment E01-011 (HKS) achieved ~500 keV FWHM 12B : reference data with the best resolution 7He : first reliable observation of ground state binding energy 28Al : first observation, opened doorway to medium-heavy hypernuclei The 3rd generation experiment E05-115 (HKS-HES) measured L, S0, 7He, 9Li, 10Be, 12B, 52V With a high quality electron beam from MAMI-C (e,e’K) hypernuclear spectroscopy will continue in 2o11

P(γ,K+)Λで生成断面積が最も

Goals of future experiments High precision on ground state light hypernuclei Resolution: ~130 keV FWHM; mass precision : < ±30 keV Precise  binding energy Charge symmetry breaking Linkage between structures of hypernuclei and nuclei Determining ground state spin/parity Search for Isomeric low lying states (Isomerism) Study the drip line limit on -hypernuclei, such as heavy hyper-hydrogen: 6H, 7H, and 8H Medium modification of baryon property