1. Hypernuclear Spectroscopy with Electron Beams
Patrick Achenbach (U Mainz)
for the E Collaboration at JLab
for the A1 Collaboration at MAMI
27 Jan 2o11

2. Production of hypernuclei
[CERN ( )]
secondary kaon- or pion beams
[SKS ( and 2011+)] n p L

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

4. 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

5. 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).]

6. 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

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

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

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

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

11. 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

12. Hypernuclear isotopes detected at JLab

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

14. 12C(e,e’K+)12LB, 12C(p+,K+)12LC
reference spectrum with best resolution

15. 28Si(e,e’K+)28LAl, 28Si(p+,K+)28LSi#1 #2 #3
first d-shell hypernuclear
spectroscopy by (e,e’K+)

16. 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]

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

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

19. 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)

20. 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

21. 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
8Li + -
116.40
n + 8Li
-3.756
8Be + -
124.12
2p + 7H
(B=6.1)
7He + -
135.17
~270
d + 7He
7Li + -
114.61
2n + 7Li
7Be + -
108.02
3He + 6H
(B=5.1)
6He + -
133.47
3H + 6He
-9.745
6Li + -
108.39
3n + 6Li
6Be + -
100.58
~220
 + 5H
(B=4.1)
5He + -
133.42
~900
n +  + 4H
4He + -
132.95
6He + 3H
3He + -
114.29
[from Liguang Tang]

22. Summary With a high quality electron beam from CEBAF
(e,e’K) hypernuclear spectroscopy was established
The 2nd generation experiment E (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 E (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

23. P(γ,K+)Λで生成断面積が最も

24. 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