Hypernuclear spectroscopy using (K-stop,p0) 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 1953. M. Danysz i J.Pniewski discovery in photographic emulsion (26km) Disintegration modes

Historical overview Binding energy known for cca 30 hypernuclei BL= Mcore+ ML- Mhyp 1953-1970: visual experimental techniques (emulsions, bubble chambers). 1970® today spectrometry with particle beams from accelerators

particle the most interesting hyperon! Q=0 I=0 S=-1 tL=263 ± 2 ps The lightest hyperon 1115.684 ± 0.006MeV mass cca 20% larger than n or p mass

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

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

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)

Reaction type: (K-(stop),p0) E907 pK=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 3.429 mm Thickness of cathode foil 0.0127 mm Number of cathode strips per plane 64 Capacitance between two strips 12 pF Single strip resistance 0.11W/mm Total number of anode planes 10 Thickness of a single anode plane 3.429 mm Anode wire diameter 0.02 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 3.429 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 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

Experimental details E01-011 Ee 1.8 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).

Electron arm E01-011

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)

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. = -11.81 MeV B p.s = -0.79 MeV p (3+/2+s) C.E #1 Counts (0.15 MeV/bin) C.E #2 Accidentals B (MeV)

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. = -18.47 MeV B p.s = -7.30 MeV B (MeV)

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. = -5.69 MeV Counts (0.2 MeV/bin) Accidentals B (MeV)

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

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

G0: E99-016, E01-115 and E01-116 parity-violating asymmetries in elastic electron scattering from the nucleon