JLabにおける(e,e`K+)反応を用いた精密ラムダハイパー

JLabにおける(e,e'K+)反応を用いた
精密ラムダハイパー核分光実験
東北大学理学研究科
後神利志
Toshiyuki Gogami
Strangeness 2010 at KEK
June2009 @ JLab Hall-C
Contents
• Introduction
– (e,e’K+)
– JLab , CEBAF
• JLab E05-115 experiment
– Motivation
– Setup
– Analysis
• Summary
Strangeness 2010 at KEK
Spectroscopic experiment
via (e,e’K+) reaction
Feynman diagram
e
p
e
u
u
d
γ* u K+
–s
s
u Λ
d
e + p ➝ e’ + K+ + Λ
e-
γ*
p
n
Λ
K+
target nucleus
measure
Missing mass : M2HY = (Ee + MT - EK+ - Ee’)2 - ( pe - pK+ - pe’)2
•Binding energy
•Cross section
(e,e’K+) reaction
(e,e’K+)
(π+ , K+)
(K- , π-)
e + p ➝ e + K+ + Λ
π+ + n ➝ K + + Λ
K - + n ➝ π- + Λ
e
Reaction
p
e
u
u
d
γ* u K+
–s
s
u Λ
d
Momentum transfer
(Typical )
~300 [MeV/c]
Λ’s Spin
At forward angle
flip ≈ non-flip
Spin dependent structure
proton
Mirror lambda hypernuclei
Beam
High quality , high intensity
Energy resolution
(FWHM)
u +
–s K
d
n d
u
s
d Λ
u
~300 [MeV/c]
–u
s
–u
d π
d
n d
u
s
d Λ
u
K-
~90 [MeV/c]
Λ can be bounded in deeper orbit
Λ’s from
Target
u
–
d
π+
primary
non-flip
non-flip
neutron
neutron
secondary
secondary
Thin (~100 mg/cm2)
Thick(> a few [g/cm2] ) Thick(> a few [g/cm2] )
(Isotopically enriched)
≤ 500 [keV]
Fine structure
1 – 3 [MeV]
1 – 3 [MeV]
JLab CEBAF ( Continuance Electron
Beam Accelerator Facility )
• (e,e’K+) experiment
1.
2.
3.
Coincidence experiment
(K+ and e-)
Small cross section
( ~100 [nb/sr] ) 1/1000
Energy resolution
sub MeV (FWHM)
• Requirement for accelerator
1. high duty factor
2. high intensity
3. small emittance
small ΔE/E
CEBAF can satisfy
these requirements
Maximum beam energy
6.0[GeV]
Maximum beam intensity
200[μA/Hall]
Beam emittance
~2 [mm・μrad]
Thomas Jefferson
Beam energy spread
National Accelerator Facility
100 [m]
Beam bunch interval
<1×10-4
nd Indian-summer school
22~2[ns]
(499[MHz])
(SNP2010)
(e,e’K+) experiment in JLab Hall-C
2000年
1st generation exp. JLab E89-009
ENGE(e’) + SOS(K+)
12 B
Λ
~ 900 [keV] (FWHM)
Proof of feasibility
2005年
Luminosity ×137
e’ rate
1/200
S/N
×2.7
2nd generation exp. JLab E01-011
ENGE(e’) + HKS(K+) + Tilt method
7 He,12 B,28 Al
Λ
Λ
Λ
~ 500 [keV] (FWHM)
Establish
exp. method
2009年
Medium heavy
3rd generation exp. JLab E05-115
HES(e’) + HKS(K+) + Tilt method
7 He,9 Li,10 Be, 12 B,52 V
Λ
Λ
Λ
Λ
Λ
≤ 500 [keV] (FWHM)
Strangeness 2010 at KEK
E05-115 experimental motivation (1)
•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 “
• Medium heavy (52Λ V)
 s-,p-,d-,f-orbit binding energy
& cross section
 Mass dependence of Λ single
particle energy
 l・s splitting ∝ 2l+1
BΛ [MeV]
12
• p-shell(7ΛHe , Λ9Li , 10
Λ Be , Λ B)
 Charge symmetry breaking
 Λ-Σ coupling
A = 52
E05-115 experimental motivation(2)
FULL(8)
FULL(4)
・・
・
1f7/2
1d3/2 FULL(4)
・・
・
n = 28
p = 24
52Cr
52
ΛV
7+ or
6+ f
6- or
5+ or
5- d
4- or
3- s
4+ p
ls splitting ∝ 2l+1
Λ
• ls splitting
• Core excited
Photo- and electro production of medium
mass Λ-hypernuclei ,P.Bydzovsky et al. (2008)
22nd Indian-summer school (SNP2010)
JLab E05-115 experimental setup
e + p → e’ + Λ + K+
2×10-4
7 [msr]
3 – 12 [deg]
7Li
2×10-4
11 [msr]
2 – 12 [deg]
, 9Be , 10B , 12C , 52Cr
Strangeness 2010 at KEK
HKS detectors
June 2009 in JLab Hall-C
1 [m]
HKS trigger
•CP = 1X ×1Y × 2X
•K = WC × AC
 CP × K
−
~18 [kHz]
(8 [μA] on 52Cr)
p
K+
π+
K+
p, π+
Cherenkov detectors -AC,WC• Aerogel (n=1.05)
• Water (n=1.33)
TOF walls -2X,1Y,1X(Plastic scintillators)
TOF σ ≈ 170 [ps]
Strangeness 2010 at KEK
Drift chambers
-KDC1,KDC2σ ≈ 250 [μm]
HES Detectors
HES D magnet
Drift chambers
- EDC1 , EDC2 TOF walls - EH1 , EH2 (Plastic scintillators)
σ ~ 300 [ps]
Time Of Flight
HES trigger
EH1 × EH2
e
~2 [MHz]
(8 [μA] on 52Cr)
Strangeness 2010 at KEK
Data summary E05-115 ( 2009 Aug – Nov )
Physics Data
Target
Hypernucleus
7Li
Current [μA] Total charge[C]
32.0
4.84
2000 / 7 / 0.9
9Li
188.1
38.3
5.33
2400 / 9 / 1.6
56.1
38.7
6.25
1300 / 1 / 0.1
1200 / 5 / 1.0
(@36μA)
2000 / 17 / 1.8
10Be
Λ
12C
12B
112.5
26.8
5.90
52Cr
52V
134.0
154.0
7.6
0.83
5.53
Λ
Λ
Calibration Data
Target
Typical rate
HES/HKS/COIN
[kHz]
184.0
Λ
10B
Beam
7He
Λ
9Be
Thickness
[mg/cm2]
Hypernucleus
Thickness
[mg/cm2]
CH2
Λ , Σ0
450.8
H2O
Λ , Σ0
~500.022
Beam
Current[μA]
Total charge[C]
2.0
0.28
nd
Indian-summer school (SNP2010)
2.7
0.20
Analysis process
HES
HKS
tracking
x , x’ , y , y’
at Reference plane
tracking
p(e,e’K+)Λ
450.8 [mg/cm2]
2.0 [μA]
38 [hours]
x , x’ , y , y’
at Reference plane
p(e,e’K+)Σ0
σ = 2 [MeV/c2]
(NOT TUNED)
F2T function
x’ , y’ , p
at target
x’ , y’ , p
at target
Missing Mass
tune
F2T function
particle ID
(select K+)
tune
Tracking for high multiplicity
52
CHCr2 target
particle
particle
Blue : selected wires
Black: hit wires
mean ~ 26 hit
52Crtarget
CH
2 target
Tracking eff.
Multiplicity of typical layer
CH2
KDC1 tracking
52Cr
Traditional JLab Hall-C tracking code
cannot handle with high multiplicity
data.
Developing new code
Multiplicity
Strangeness 2010 at KEK
Summary
• 3rd generation exp. E05-115 experiment
– 2009 Aug – Nov @JLab Hall C
first try to measure Λ-hypernuclei
7
9
10
12
52
– ΛHe, ΛLi, Λ Be, ΛB, Λ V
up to A=52 via (e,e’K+)
– Spectrometers and Detectors work well
– Now analyzing
•
Tracking for high multiplicity
END
ありがとうございました
Strangeness 2010 at KEK

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