Hypernuclear spectroscopy using (K-

stop,0) and (e,e’K+) reactions

Doc. dr. sc. Darko AndroićUniversity of ZagrebPhysics 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

0

-3

-4

-4

-4

p (63.9±0.5%)

(35.8±0.5%)

(1.75±0.15 10 )

p (8.4 ±1.4 10 )

pe (8.32±0.14 10 )

p (1.57±0.35 10 )

e

n

n

v

v

Historical overview 1953-1970:

visual experimental techniques (emulsions, bubble chambers).

1970today spectrometry with particle beams from accelerators

Binding energy known for cca 30 hypernucleiB= Mcore+ M- Mhyp

particlethe most interesting hyperon!

The lightest hyperon 1115.684 ± 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 NNN sensitive for difference

between baryon-baryon interaction and quark level processes

:

:

:

:

o

m

o

nm

p

n

p

n

p n p

n n n

Excited states of hypernucleiand 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 protonreaction types (K-,0) i (-,K0)

Reaction type: (K-

(stop),0) E907

12 0 12( , )C K B

1 2 2

1 2

1 2

2

(1 cos )(1 )o oE E E m

X

E EX

E E

pK=682MeV/c

NMS and beam line detectorsE907

12 0 12( , )C K B

Active target E907

12 0 12( , )C K B

ATC parameters

Total number of the targets 4Thickness of individual targets 12.7 mmTarget material GraphiteTotal number of cathode planes 20Thickness of single cathode plane 3.429 mmThickness of cathode foil 0.0127 mmNumber of cathode strips per plane 64Capacitance between two strips 12 pFSingle strip resistance 0.11/mmTotal number of anode planes 10Thickness of a single anode plane 3.429 mmAnode wire diameter 0.02 mmWire material gold-plated tungstenAverage anode wire tension 72 gAnode potential 2.2 kVTotal number of spacer boards 10Thickness of spacer boards 3.429 mm

Resolution E907

12 0 12( , )C K B

ResultsE907

12 0 12( , )C K B

E931

4 0 4( , )He K H

Topology and calibrationE931

4 0 4( , )He K H

Particle identificationE931

4 0 4( , )He K H

Neutron spectrum / coincidencesE931

Important theoretical contribution: Zagreb theoretical group of prof. D. Tadić

4 0 4( , )He K H

Electroproduction vs meson production of hypernuclei

Experiment topologyE89-009

12 12( , ´ )C e e K B

12 12( , ´ )C e e K B

Event reconstructionE89-009

SpectrumE89-009

12 12( , ´ )C e e K B

Firstelectroproduction

E89-009

12 12( , ´ )C e e K B

Experiment topologyE01-011

( , ´ )e e K

HKS detailsE01-011

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

( , ´ )e e K

Experimental detailsE01-011

Ee 1.8 GeV Ee’ 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).

( , ´ )e e K

( , ´ )e e K

Electron armE01-011

p(e,e’Kp(e,e’K++))&&00 used for kinematics and optics calibration used for kinematics and optics calibrationC

ou

nts

(30

0 ke

V/b

in)

B (MeV)

Preliminary

Preliminary

HKS-JLABHKS-JLAB

CHCH22 target target

~ 70 hours~ 70 hours

= 630 keVM = 24 keVM = 8 keV

00

( , ´ )e e K

1212C(e,e’KC(e,e’K++))1212BB used for kinematics and optics calibration used for kinematics and optics calibration

Co

un

ts (

0.15

MeV

/bin

)

s

(2-/1

-)

p

(3+

/2+

s)

JLAB – HKSJLAB – HKS

~ 90 hrs w/ 30~ 90 hrs w/ 30A A

Preliminary

Preliminary

AccidentalsAccidentals

B (MeV)

= ~400 keV FWHMB g.s. = -11.81 MeV

B p.s = -0.79 MeV

C.E #1

C.E #2

( , ´ )e e K

AccidentalsAccidentalsCo

un

ts (

0.15

MeV

/bin

)2828Si(e,e’KSi(e,e’K++))2828

AlAl – First Spectroscopy of – First Spectroscopy of 2828AlAl

JLAB – HKS ~140 hrs w/ 13JLAB – HKS ~140 hrs w/ 13AA PreliminaryPreliminary

s

p

B (MeV)

= ~400 keV FWHMB g.s. = -18.47 MeV

B p.s = -7.30 MeV

( , ´ )e e K

AccidentalsAccidentals

B (MeV)

Co

un

ts (

0.2

MeV

/bin

)77Li(e,e’KLi(e,e’K++))77

HeHe – First – First ObservationObservation of ½ of ½++ G.S. of G.S. of 77HeHe

PreliminaryPreliminary JLAB – HKS (~ 30 hrs w/ 30JLAB – HKS (~ 30 hrs w/ 30AA ))

s = ~467 keV FWHMB g.s. = -5.69 MeV

( , ´ )e e K

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

( , ´ )e e K

HES schemeE05-115

2.5 GeVelectron

7.5o “tilt”

HESHKS

Target

e’

K+

( , ´ )e e K

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 E01-116parity-violating asymmetries in elastic electron scattering from the nucleon