Hypernuclear spectroscopy using (K - stop, 0 ) and (e,e’K + ) reactions Doc. dr. sc. Darko...
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Transcript of Hypernuclear spectroscopy using (K - stop, 0 ) and (e,e’K + ) reactions Doc. dr. sc. Darko...
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