1. Hypernuclear spectroscopy using (K-stop,p0) and (e,e’K+) reactions
Doc. dr. sc. Darko Androić
University of Zagreb
Physics Department

2. Definition and discovery
Hyperon – baryon with at least one strange quark
Hypernucleus – nucleus with at least one hyperon
1953. M. Danysz i J.Pniewski discovery in photographic emulsion (26km)
Disintegration modes

3. Historical overview Binding energy known for cca 30 hypernuclei
BL= Mcore+ ML- Mhyp
: visual experimental techniques (emulsions, bubble chambers).
1970® today spectrometry with particle beams
from accelerators

4. particle the most interesting hyperon!
Q=0
I=0
S=-1
tL=263 ± 2 ps
The lightest hyperon
± 0.006MeV
mass cca 20% larger than n or p mass

5. Summary: hypernuclei from emulsion
Binding energy: BL ~ A (cca 1MeV/A)
Binding energy difference for mirror nuclei DBL<< 0.5MeV
n= Gn / Gp+Gn cca 1/3
Q- = Gnm / Gm ~ A
LN improving understanding of NN interaction
LN®NN sensitive for difference between baryon-baryon interaction and quark level processes

6. Excited states of hypernuclei and spectroscopy
Using strange particle beams (K±)
Detector systems - fragment identification

7. Former experiments L production on neutron
reactions types (K-,p-) i (p+,K+)
“mirror nuclei” have to be investigated in reactions with simultaneous changing charge and strangeness
L production on proton
reaction types (K-,p0) i (p-,K0)

8. Reaction type: (K-(stop),p0) E907
pK=682MeV/c

9. NMS and beam line detectors E907

10. Active target E907 ATC parameters Total number of the targets 4
Thickness of individual targets mm
Target material Graphite
Total number of cathode planes 20
Thickness of single cathode plane mm
Thickness of cathode foil mm
Number of cathode strips per plane 64
Capacitance between two strips 12 pF
Single strip resistance W/mm
Total number of anode planes 10
Thickness of a single anode plane mm
Anode wire diameter mm
Wire material gold-plated tungsten
Average anode wire tension 72 g
Anode potential kV
Total number of spacer boards 10
Thickness of spacer boards mm

11. Resolution E907

12. Results E907

13. E931

14. Topology and calibration E931

15. Particle identification E931

16. Neutron spectrum / coincidences E931
Important theoretical contribution:
Zagreb theoretical group of prof. D. Tadić

17. Electroproduction vs meson production of hypernuclei

18. Experiment topology E89-009

19. Event reconstruction E89-009

20. Spectrum E89-009

21. First electroproduction E89-009

22. Experiment topology E01-011

23. HKS details E01-011 Magnet configuration Q-Q-D Momentum acc.
1.2 GeV/c ± 12.5%
(1.05–1.35 GeV/c)
Momentum resolution
(Dp/p) 2×10−4
angle 30 (16) msr
position: 7◦(1–13◦)
trajectory 10 m
Magnetic field 1.6 T

24. Experimental details E01-011
Ee GeV
Ee’ 300 MeV
Virtual photon energy 1.5 GeV
p(g,K+)L decreases for Eg > 1.5 GeV
New redesign:
1- New kaon spectrometer HKS (dipole 210t)
two quadruple Q1 (8.5 t) i Q2 (10.5 t)
2- new geometry of electron spectrometer (tilt method).

25. Electron arm E01-011

26. p(e,e’K+)&0 used for kinematics and optics calibration
HKS-JLAB
CH2 target
~ 70 hours 
 = 630 keV
M = 24 keV
M = 8 keV
Counts (300 keV/bin)
Preliminary 0
B (MeV)

27. 12C(e,e’K+)12B used for kinematics and optics calibration
JLAB – HKS
~ 90 hrs w/ 30A
s (2-/1-)
Preliminary
 = ~400 keV FWHM
B g.s. = MeV
B p.s = MeV
p (3+/2+s)
C.E #1
Counts (0.15 MeV/bin)
C.E #2
Accidentals
B (MeV)

28. 28Si(e,e’K+)28Al – First Spectroscopy of 28Al
Preliminary
JLAB – HKS ~140 hrs w/ 13A p s
Counts (0.15 MeV/bin)
Accidentals
 = ~400 keV FWHM
B g.s. = MeV
B p.s = MeV
B (MeV)

29. 7Li(e,e’K+)7He – First Observation of ½+ G.S. of 7He
Preliminary
JLAB – HKS (~ 30 hrs w/ 30A ) s
 = ~467 keV FWHM
B g.s. = MeV
Counts (0.2 MeV/bin)
Accidentals
B (MeV)

30. Conclusion / Future experiment
Hypernuclear electroproduction demonstrated kinematical completeness
Superior resolution respect meson production experiments
(e,e´K+) channel is charge-mirrored respect (K±,p±); new insight
possible quark degrees of freedom have to be included in theoretical calculations
Future resolution improvements are required

31. HES scheme E05-115 HKS HES e’ 7.5o “tilt” K+ Target 2.5 GeV electron
JLab E (HES):
Extend hypernuclear Spectroscopy
from lower p-shell to beyond p-shell
with a few 100 keV resolution

32. G0: E99-016, E and E parity-violating asymmetries in elastic electron scattering from the nucleon