Electrophoto-production of strangeness and Hypernuclei
Osamu HashimotoDepartment of Physics, Tohoku University
October 21-22, 2004Jeju University
Strangeness production by pions and photons
21 1.2 1.4 1.6 1.8
σto
tal(
b)
1.0
2.0
Eγ(GeV)
p(,K+) Total cross section
Phys. Lett. B 445, 20 (1998)M. Q. Tran et al.
Basic characteristics of the (e,e’K+) spectroscopy
Proton converted to Neutron rich hypernuclei
Large angular momentum transfer Similarly to (+,K+) reactionSpin-flip amplitude Unnatural parity hypernuclear statesHigh quality primary beam Sub MeV resolution
The (e,e’K+) reactions --- elementary and hypernuclear ---
termsdependentspinggg
termtindependenspinf
gggfkEEEpk
EEEpdd
LKK
K
lab
:,,
:
)(cos)((
)2(
110
0
21
21
20
20
24
Elementary process
Hypernuclear production
2tan
21
1
2,
12
22
2
2'
22
*
'
3
e
pe
e
KKe
mqE
EEE
Q
dd
dddd
nK0reaction data near the threshold play an important role
• No contribution from the t-channel Born term• Less contribution of resonances terms
Isobar model
Elementary processes of photo-strangeness production
•g(K00n) = -g(K+0p)
Coupling constantsResonances to be included
New high-quality data being available for K+
However,
Six possible isospin channels: (1) p(,K+) (2) p(,K+)0
(3) p(,K0)+
(4) n(,K+)-
(5) n(,K0) (6) n(,K0)0
n(,K) Model calculation
γ + n → K0 + Λ
Energy dependence Angular distribution
calculated by Sotona’s code
γ + p → K+ + ΛEγ = 1.05 GeV
Eγ = 1.05 GeV
Kaon-MAID: T.Mart, C.Bennhold, Phys. Rev. C61 (2000) 012201(R) http://kph.uni-mainz.de/MAID/ kaon/kaonmaid.htmlSLA: T.Mizutani et al., Phys. Rev. C58 (1998) 75.
Laboratory for Nuclear Science, Tohoku University at Sendai
Neutral Kaon Spectrometer
( NKS )
• 200 MeV LINAC• 1.2 GeV Booster/stretcher ring• エネルギー標識化光子ビーム
• up to 1.1 GeV/c• Good duty factor
First observation of neutral kaons in the threshold region
K0 ~ 450
Background
Invariant Mass () (GeV/c2)
coun
ts/2
0MeV
K0s: c2.68cm
12C target
Ks0 + + - (64 %)
solid: Kaon-MAID n(,K0)onlydashed: Kaon-MAID include p(,K0)+ + n(,K0)0
solid: SLA n(,K0)
Neff = 4.2kF
0=0.22GeV/c
Comparison with recent models + 12C K0 + X
( Quasi-free K0 production)
preliminary
preliminary
Neutral kaons from the liquid deuterium targetK0
S : c ~ 2.68 cm
x ~ 1.6mm
Comparison of D2 target data
with theoretical models
preliminary
Upgrade plan at LNS, Tohoku
STB ringradiator
1.2 GeV e-
NKS2
Pole diameter : 160 cmBMAX : 0.5 T
High momentum & mass resolutionEfficiency more than 2X for K0
Efficiency more than 10 x for Ready in 2005
K+ detection At very forward angle (~ 0 degrees) Maximum hypernuclear production cross section
e’ detection At extremely forward angles Advantage : Large virtual photon flux Disadvantage : Huge backgrounds from Bremsstrahlung
Hypernuclear production by the (e,e’K+) reaction
pe=0.3GeV/c e’
K+
pK=1.2 GeV/c
Ee=1.8 GeVe- Beam
Target nucleus
E=1.5 GeV
Angular distribution of electrons and kaons
Ee = 1.864 GeVEe’=0.4 GeVEe = 1.864 GeVEe’ = 0.38 GeV
angle (deg)
d/d
(nb/
sr)
electrons kaons(degrees) Calculated
by Sotona’s code
Jlab Accelerator
Hall BHall A Hall C
Beam characteristicsEmax 6 GeV Max. Current 200 ADuty factor 100%Emittance 2.0 m·mradEbeam 2.510-5 (FWHM)
E89-009E01-011
E97-107
E89-009 experimental setup
To beam dump
E89-009 calibration
p(e,e’K+) p(e,e’K+)
12C(e,e’K+) quasi-free
Accidental
e
e’ e+ e-
815 keV(FWHM)
CHx target
A(e,e’;(e+,e-))A
138nb/sr
12B spectrum of E89-009
d/d
nb/
sr/0
.3 M
eV
-B(MeV)
-15 0 5 10 15-5-10
(2+,3+)(1-,2-)
(1-,0-)
(2-,1-)
40
50
60
70
80
90
Ground state doublet
B = 11.52±0.35 MeV
Cross section 140±17(stat) ±18(sys) nb/sr
Motoba’s calculation
J cross section 1- 23.4 nb/sr 2- 114.5 nb/sr
Binding energy
Emulsion data B = 11.37 MeV
750 keV(FWHM)
1 month data
7He Spectrum of E89-
009
• No peaks observed in the bound region• A suggestive bump at around 7-8 MeV
d/d
nb/
sr/0
.3 M
eV120
140
160
180
200
7Li(e,e’K+)7He
20
40
60
80
-20-10 10 200
-B ( MeV)-10 -5 10 15 2050
0.01
0.02
0.03
0.04
)/( srbdd
6
He + n6He +
5/2+
3/2+
3/2-
1/2+
5/2-
7/2-3/2-
5/2-
-B ( MeV)Shell model calc. by Sotona
E~400 keV
12C (e,e’K)12BVery Preliminary
Data
with Multiple Uncorrected Beam Energies
“Standard” PID
Full statistics with fitted peaks. Resolution still not fully optimizedSubsets of data appear to have better resolutionLimited statistics
+ cut on Beam x position at 1C12+ ± 50 keV on relative beam energy
E=1.3 MeV (FWHM)
Guarantees beam within specs
Projected Data
Beam energy spread and spectrometer resolutions as planned
E~800 keV
From Prof. Garibaldi
HALL A
Hypernuclear spectroscopy experiments at Jlab
Area Ee(GeV)
E
(GeV)
e
(deg.)
pK
(GeV/c)
K
(deg.)Spectromete
rsRun year
E89-009
Hall C
1.7-1.8 1.5 0 1.2 0-7
SOS+ENGE,
Splitter2000
E94-107
Hall A 4 1.9 6 1.9 6 HRS+HRS,
Septum 2004
E01-011
Hall C 1.8 1.5 4.5 1.2 0-14
HKS+ENGE (Tilt),
Splitter2005
??? Hall C
2.2-2.5 1.5 ~3 1.2 0-14
HKS+HES,New
splitter2007?
MAINZ to join
The tilt method for higher luminosity
Side view
Future spectrometer system for the (e,e’K+) reaction
High resolution Electron Spectrometer
HES
(2.2~2.5GeV)
Yield comparison of E01-011 and E89-009
Item E01-011 E89-009 Gain
factorVirtual photon flux per
electron(x10-4)0.2-0.35 4 0.05-
0.0875Target
thickness(mg/cm2) 100 22 4.5
Scattered electron momentum
acceptance(MeV/c)150 120 1.2
Kaon survival rate 0.35 0.4 0.88Solid angle of K arm 16 5 3.2
Beam current(A) 30 0.66 45Estimated yield (12
Bgr:counts/h) ~500.9
(measured)
60
Expected 28Al hypernuclear
spectra
SKS E140a
28Si(+,K+)28Si
Summary
Photo strangeness production in the 1 GeV regionNeutral kaon measurement plays a unique roleNKS at LNS, Tohoku measured neutral kaonsNKS2 for further experimental study of neutral kaon production is under construction
Hypernuclear production by the (e,e’K+) reactionThe first 2 experiments were successfully carried out at Jlab Hall C and Hall A2nd generation hypernuclear spectroscopy by the (e,e’K+) reaction is to be carried out in 2005High resolution electron spectrometer is under construction for the 3rd generation (e,e’K+) spectroscopy
Etop2pass
(GeV)
Acceptable energy windows of HKS systemwith ENGE or HES revised 04/10/10
10.55
0.40.3 0.6 0.8
Ee’ (GeV)2.51.8 1.9Ee at Hall
(GeV)
Acceptable Central Energy
(GeV)
HESENGE
2.0 2.2 2.4
Etop1pass
(GeV)
4.4 4.55 5.0 6.0
9.45 10.3 10.8 12.0
2.05
0.65
2.15
Invariant mass spectrum
Invariant mass [GeV/c2]
K0 mass region 0.46 – 0.54 GeV/c2
accidental events
miss ID events
k0 candidates
Momentum distribution
Error : statistical only
Virtual photon energy E1.5 GeV
Beam energy Ee= 1.721, 1.864 GeV
Reaction Threshold(MeV)p KKKK*(892)
21 1.2 1.4 1.6 1.8
σtotal(b)
1.0
2.0
Eγ(GeV)
Tota
l cro
ss se
ctio
n
Phys. Lett. B 445, 20 (1998)M. Q. Tran et al.
Experimental Experimental conditioncondition
Limited by bremsstrahlung electrons at 0 deg.in scattered electron spectrometer
p(, K+)
Beam current < 2 A
< 0.6 A for 12C target
Target thickness < 100 mg/cm2
natC 22 mg/cm2
CH2 8.8 mg/cm2
XN
i totalKTK dNNdd
1
11
NT : target densityNX : or 12
B g.s yield N : Number of virtual photon integrated over Ee’ and e’ total : total correction factor
Cross sectionCross section
Cross sections were extracted with experimental yields
.deg0''
KKee dd
ddEdd
Triple-differential cross section
)2
tan/2(1
1
'1
)2/(
222
22
e
e
e
EEE
QΓ
1212B spectrum fitting resultsB spectrum fitting results
Fitted by 3 Gaussians and a constant Energy resolution was fixed 0.9 MeV(FWHM) Constant = 5±1 nb/sr/400keV
Energy level of Energy level of 1212B B
spectrumspectrum
Emulsion dataB=11.37±0.06 MeV
3/2 -
1/2 -
3/2 -5.0
2.10.26
0.20
1.72
S factor12C(e,e’p)11B
11B x s 12B
Ex(MeV) d/d(nb/sr)
2.51
5.44Ex(MeV)
B(g.s)=12.20±0.06±0.25 MeV :
30±15±4
59±14±7
122 ±12 ±15
1212B spectrum v.s B spectrum v.s 1212
C spectrumC spectrum
12C KEK E369
Structure is similarS and P states are observed
S
P
S
P
E=1.3GeV, =3deg., 900 keV(FWHM), NSC97f
DWIA calculation with phenomenological potential by Motoba
Theoretical prediction of Theoretical prediction of 1212B B
spectrumspectrum
Theoretical calculation of Theoretical calculation of 2828Al Al
spectrumspectrum
300 keV(FWHM)
ls splitting ???high spin and unnatural parity states
Calculated by Sotona et al.
DWIA calculation by a code of M.Sotona
Angular distributionAngular distribution of 12
B states
(p3/2)-1(p3/2) 3+
(s1/2)-1(p1/2) 2-
(p3/2)-1(s1/2) 2-
(s1/2)-1(s1/2) 1+
Expected yield ratio between g.s.
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