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Lambda hypernuclear spectroscopy up to medium
heavy mass number at Jefferson Lab
Graduate school of science, Tohoku University
Toshiyuki Gogami
for the HES-HKS collaborations
Contents
• Introduction
• Experimental setup
• Analysis
• summary
2012/10/6
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Introduction
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Spectroscopic experiment
by (e,e’K+) reaction
Feynman diagram
e
p
e
u
u
d
γ* u K+
–s
s
u Λ
d
e’-Spectrometer
eγ*
p
n
Λ
target nucleus
~ 1990’s
(K-,π-) , (π+,K+) reactions
• Energy resolution ~ a few MeV
• n Λ
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pe’
e + p ➝ e’ + K+ + Λ
Missing Mass HHY
K+
K+-Spectrometer
pK+
2000~
(e,e’K+) reaction
• Energy resolution ~500keV
• pΛ
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E05-115 experimental motivation
•2009 Aug – Nov @ JLab Hall-C
•(e,e’K+) reaction
First try
•Target : 7Li , 9Be , 10B , 12C , 52Cr
It is difficult experimentally.
“ b.g. electron due to brems. ∝ ~Z2 “
• Light Λ hyprenuclei (7ΛHe,9ΛLi,10Λ Be,12ΛB)
•
Medium heavy Λ hyprenuclei (52
Λ V)
 s-,p-,d-,f-orbit binding energy
& cross section
 Mass dependence of Λ single
particle energy
 l・s splitting ∝ 2l+1
•
Λ, Σ0
 Energy scale calibration
 Elementary process
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BΛ [MeV]
 Charge symmetry breaking
 Λ-Σ coupling
A = 52
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Experimental setup
& Trigger
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Experimental setup
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Detectors & Trigger
HES
K+
eTOF walls
(Plastic scintillators)
HKS
p, π+
Cherenkov detectors
• Aerogel (n=1.05)
• Water (n=1.33)
Drift chambers
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Detectors & Trigger
HES
K+
e-
HES trigger
(TOF1x2)
~2000 kHz
TOF walls
(Plastic scintillators)
HKS
p, π+
HKS trigger
(TOF1x2x3) x Chrenkov
Cherenkov detectors
~10 kHz
• Aerogel (n=1.05)
• Water (n=1.33)
Coincidence
trigger
Drift chambers
HES x HKS
< 2 kHz
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Analysis
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Analysis process
HKS
raw data decoding tracking
x , x’ , y , y’
at Reference plane
ITERATION
F2T function
x’ , y’ , p
at target
KID
Missing mass
F2T func. Tuning
x’ , y’ , p
at target
F2T function
raw data decoding tracking
HES
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x , x’ , y , y’
at Reference plane
ITERATION
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Gogami
Coincident K+ Identification (OFF-LINE)
Cherenkov selection
Water (n=1.33)
Coincidence time selection
Aerogel (n=1.05)
( e,e’p )
K+ +
π
CUT
( e,e’K+ )
CUT
CUT
CUT
CUT
CUT
p
( e,e’π+ )
= HKST - HEST
p cut
π+ cut
Coincidence of (e,e’K+) selection
mK2 selection
Coincident K+ : ~90% ( π+ : < 1% , p : < 2% )
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e , e+ backgrounds in HKS
HES
HKS
SIMULATION
e,
+
e
Vacuum chamber
(sus304)
e+ from the target
NMR port
(sus304)
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•
•
•
•
•
Generated particle : e+
Distribution : spherical uniform
Momentum : 860 – 1000 [MeV/c]
Angle : 0 – 2 [mrad]
1000 events
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Analysis for medium-heavy Λ hypernuclei
• Conventional tracking code in JLab Hall-C cannot handle high multiplicity data.
 New tracking routine is developed
• Parameters are totally different from those of lower multiplicity data.
 Parameter optimization is in progress
HKS Detectors
450±80
Accidental Coincidence
EVENT DISPLAY (REAL DATA)
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52Cr(e,e’K+)52 V
Λ
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Λ, Σ0 from CH2 target
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Gogami
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Λ, Σ0 from CH2 target
JLab E05-115
CH2, ~ 450 [mg/cm2]
~ 2.0 [μA]
~ 38 [hours]
p(e,e’K+)Λ
~1.8MeV (FWHM)
Δm = 19 ± 17 keV/c2
p(e,e’K+)Σ0
~1.8MeV (FWHM)
Δm = 73 ± 47 keV/c2
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Preliminary results of K+Λ electro-production
• Reducing
systematic error
• Consistency
JLab E05-115
check by using
194 ± 6 ± 97
H2O target.
SAPHIR : K.H.Glander et al. , Eur. Phys. J. A 19, 251-273 (2004)
CLAS : R.Bradford et al. , Phys. Rev. C 73, 035202 (2006)
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Comparison with data of
JLab Hall-A
p(γ*,K+)Λ ~ JLab E05-115 (HES-HKS)
W ~ 1.9 GeV
Q2 ~ 0.01 [GeV/c]2
Large longitudinal
term contributions?
p(γ*,K+)Λ ~ JLab E94-107
W ~ 2.2 GeV
Q2 ~ 0.07 [GeV/c]2
SAPHIR : K.H.Glander et al. , Eur. Phys. J. A 19, 251-273 (2004)
CLAS : R.Bradford et al. , Phys. Rev. C 73, 035202 (2006)
JLab E94-107 : P.Markoviz et al. , Proceedings of SENDAI08 (2009)
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Summary
• JLab E05-115 (HES-HKS) was performed in JLab Hall-C
in 2009
–
7 He,9 Li,10 Be,12 B, 52 Cr,
Λ
Λ
Λ
Λ
Λ
Λ, Σ0
• The analyses of medium-heavy target are in progress
– Tracking
– Parameter optimization
• High statistical data of p(γ*,K+)Λ
– cosθCM~0.97 , W ~1.9 GeV, Q2~0.01 [GeV/c]2
• 192±6±89 [ nb / sr ]
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HES-HKS Collaborations
2020/5/6
FB20 in Fukuoka, Toshi Gogami
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Thank you for your attention
Prof.
S.N.Nakamura
2020/5/6
Prof.
O.Hashimoto
End run party
E05-115
FB20of
in Fukuoka,
Toshi(Mar2010)
Gogami
20
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Detectors & Trigger
HES
K+
e-
HES trigger
(TOF1x2)
~2000 kHz
TOF walls
(Plastic scintillators)
HKS
p, π+
HKS trigger
(TOF1x2x3) x Chrenkov
Cherenkov detectors
~10 kHz
• Aerogel (n=1.05)
• Water (n=1.33)
Coincidence
trigger
Drift chambers
HES x HKS
< 2 kHz
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e
Photon
K+
e’
HKS
HES
e
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