Hypernuclear spectroscopy using (K - stop,  0 ) and (e,e’K + ) reactions Doc. dr. sc. Darko Androić University of Zagreb Physics Department

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

Historical overview : visual experimental techniques (emulsions, bubble chambers)  today spectrometry with particle beams from accelerators Binding energy known for cca 30 hypernuclei B  = M core + M  - M hyp

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

Summary: hypernuclei from emulsion Binding energy: B  ~ A (cca 1MeV/A) Binding energy difference for mirror nuclei  B  << 0.5MeV n=  n /  p +  n cca 1/3 Q - =  nm /  m ~ A  N improving understanding of NN interaction  N  NN sensitive for difference between baryon-baryon interaction and quark level processes

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

Former experiments  production on neutron reactions types (K -,  - ) i (  +,K + ) “mirror nuclei” have to be investigated in reactions with simultaneous changing charge and strangeness  production on proton reaction types (K -,  0 ) i (  -,K 0 )

Reaction type: (K - (stop),  0 ) E907 p K =682MeV/c

NMS and beam line detectors E907

Active target E907 ATC parameters Total number of the targets 4 Thickness of individual targets 12.7 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 0.11  /mm Total number of anode planes 10 Thickness of a single anode plane mm Anode wire diameter0.02 mm Wire material gold-plated tungsten Average anode wire tension 72 g Anode potential 2.2 kV Total number of spacer boards 10 Thickness of spacer boards mm

Resolution E907

Results E907

E931

Topology and calibration E931

Particle identification E931

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

Electroproduction vs meson production of hypernuclei

Experiment topology E89-009

Event reconstruction E89-009

Spectrum E89-009

First electroproduction E89-009

Experiment topology E01-011

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

Experimental details E E e 1.8 GeV E e’ 300 MeV Virtual photon energy 1.5 GeV p( ,K+)  decreases for E  > 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).

Electron arm E01-011

p(e,e’K + )  &  0 used for kinematics and optics calibration Counts (300 keV/bin) B  (MeV) Preliminary HKS-JLAB CH 2 target ~ 70 hours  = 630 keV  M  = 24 keV  M  = 8 keV  0000

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

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

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

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

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

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