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
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Strangeness 2010 at KEK
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
June2009 @ JLab Hall-C
Strangeness 2010 at KEK
Contents• Introduction– (e,e’K+)– JLab , CEBAF
• JLab E05-115 experiment– Motivation– Setup– Analysis
• Summary
Spectroscopic experiment via (e,e’K+) reaction
pn
γ*
ΛK+
e-
e + p ➝ e’ + K+ + Λe e
M2HY = (Ee + MT - EK+ - Ee’)2 - ( pe - pK+ - pe’)2
measuretarget nucleus
Feynman diagram
uud
ussud
–p K+
Λ
γ*
Missing mass :
•Binding energy•Cross section
(e,e’K+) reaction
uud
ussud
e e
–p K+
Λ
γ*
ud
ddu
us
sdu
– –π+
Λn
us
ddu
ud
sdu
–K-
Λn
–π-
e + p ➝ e + K+ + Λ π+ + n ➝ K+ + Λ
K+
K- + n ➝ π- + Λ(π+ , K+) (K- , π-)(e,e’K+)
Momentum transfer(Typical )
~300 [MeV/c] ~300 [MeV/c] ~90 [MeV/c]
Λ’s SpinAt forward angle
Λ’s from proton neutron neutron
flip ≈ non-flip non-flip non-flip
Beam primary secondary secondary
Target Thin (~100 mg/cm2)(Isotopically enriched) Thick(> a few [g/cm2] ) Thick(> a few [g/cm2] )
Reaction
Λ can be bounded in deeper orbit
Spin dependent structure
Mirror lambda hypernuclei
High quality , high intensity
Fine structureEnergy resolution
(FWHM)≤ 500 [keV] 1 – 3 [MeV] 1 – 3 [MeV]
JLab CEBAF ( Continuance Electron Beam Accelerator Facility )
• (e,e’K+) experiment1. Coincidence experiment (K+ and e-)2. Small cross section ( ~100 [nb/sr] ) 1/10003. Energy resolution sub MeV (FWHM)
22nd Indian-summer school (SNP2010)100 [m]
Maximum beam energy 6.0[GeV]
Maximum beam intensity 200[μA/Hall]
Beam emittance ~2 [mm ・ μrad]Beam energy spread <1×10-4
Beam bunch interval ~2[ns] (499[MHz])
• Requirement for accelerator1. high duty factor2. high intensity3. small emittance small ΔE/E
CEBAF can satisfythese requirements
Thomas Jefferson National Accelerator Facility
Strangeness 2010 at KEK
(e,e’K+) experiment in JLab Hall-C2000 年
1st generation exp. JLab E89-009ENGE(e’) + SOS(K+)
12ΛB
~ 900 [keV] (FWHM)
2005 年 2nd generation exp. JLab E01-011ENGE(e’) + HKS(K+) + Tilt method
7ΛHe,12
ΛB,28ΛAl
~ 500 [keV] (FWHM)
2009 年 3rd generation exp. JLab E05-115HES(e’) + HKS(K+) + Tilt method
7ΛHe,9
ΛLi,10ΛBe, 12
ΛB,52ΛV
≤ 500 [keV] (FWHM)
Luminosity ×137e’ rate 1/200S/N ×2.7
Proof of feasibility
Establish exp. method
Medium heavy
E05-115 experimental motivation (1)
• p-shell(7He , 9Li , 10Be , 12B) Charge symmetry breaking Λ-Σ coupling
• Medium heavy (52V) s-,p-,d-,f-orbit binding energy & cross section Mass dependence of Λ single
particle energy l ・s splitting ∝ 2l+1
•2009 Aug – Nov @ JLab Hall-C•(e,e’K+) reaction•Target : 7Li , 9Be , 10B , 12C , 52Cr
Λ Λ Λ Λ
Λ
First try
B Λ [M
eV]
It is difficult experimentally.“ b.g. electron due to brems. ~Z∝ 2 “
A = 52
E05-115 experimental motivation(2)
22nd Indian-summer school (SNP2010)
s
p d f
Photo- and electro production of medium mass Λ-hypernuclei ,P.Bydzovsky et al. (2008)
FULL(8)1f7/2
1d3/2FULL(4) FULL(4)・・・・・・sn = 28 p = 24p
d
f
4-
5+
6-
7+
3-
4+
5-
6+
Λ52ΛV
52Cr
or
or
or
or
ls splitting 2l+1∝
• ls splitting • Core excited
Strangeness 2010 at KEK
JLab E05-115 experimental setup
2×10-4
7 [msr]3 – 12 [deg] 2×10-4
11 [msr]2 – 12 [deg]
e + p → e’ + Λ + K+
7Li , 9Be , 10B , 12C , 52Cr
HKS detectors
Strangeness 2010 at KEK
K+
p, π+
Drift chambers-KDC1,KDC2-TOF walls -2X,1Y,1X-
(Plastic scintillators)
Cherenkov detectors -AC,WC-• Aerogel (n=1.05)• Water (n=1.33)
1 [m] June 2009 in JLab Hall-C
HKS trigger• CP = 1X ×1Y × 2X • K = WC × AC
CP × K
~18 [kHz](8 [μA] on 52Cr)
−π+
K+
p
σ ≈ 250 [μm]TOF σ ≈ 170 [ps]
Strangeness 2010 at KEK
HES DetectorsDrift chambers- EDC1 , EDC2 -
TOF walls - EH1 , EH2 - (Plastic scintillators)
HES D magnet
HES triggerEH1 × EH2
~2 [MHz](8 [μA] on 52Cr)e
Time Of Flight
σ ~ 300 [ps]
Target Hypernucleus Thickness[mg/cm2]
Beam Typical rateHES/HKS/COIN
[kHz]Current [μA] Total charge[C]
7Li 7He 184.0 32.0 4.84 2000 / 7 / 0.9
9Be 9Li 188.1 38.3 5.33 2400 / 9 / 1.6
10B 10Be 56.1 38.7 6.25 1300 / 1 / 0.1
12C 12B 112.5 26.8 5.90 1200 / 5 / 1.0
52Cr 52V 134.0154.0
7.6 0.835.53
2000 / 17 / 1.8
Data summary
22nd Indian-summer school (SNP2010)
Λ
Λ
Λ
Λ
Λ
E05-115 ( 2009 Aug – Nov )
Target Hypernucleus Thickness[mg/cm2]
Beam
Current[μA] Total charge[C]
CH2 Λ , Σ0 450.8 2.0 0.28
H2O Λ , Σ0 ~500.0 2.7 0.20
Physics Data
Calibration Data
(@36μA)
Analysis process
trackingx , x’ , y , y’ at Reference plane
x’ , y’ , pat target
Missing Mass
trackingx , x’ , y , y’ at Reference plane
x’ , y’ , pat target
p : Λ , Σ0 ,12ΛB
Angle : Sieve slit
F2T functionF2T function
particle ID(select K+)
HKSHES
tune tune
450.8 [mg/cm2]2.0 [μA]38 [hours]
σ = 2 [MeV/c2](NOT TUNED)
p(e,e’K+)Λ
p(e,e’K+)Σ0
Strangeness 2010 at KEK
Tracking for high multiplicity
CH2 target
particleCH2 target
mean ~ 2 hit
52Cr target
mean ~ 6 hit
52Cr target
particle KDC1 trackingBlue : selected wiresBlack: hit wires
Multiplicity of typical layer
Multiplicity
Trac
king
eff.
52CrCH2
Developing new code
Traditional JLab Hall-C tracking code cannot handle with high multiplicity data.
Summary• 3rd generation exp. E05-115 experiment– 2009 Aug – Nov @JLab Hall C– 7He,9Li,10Be,12B,52V– Spectrometers and Detectors work well– Now analyzing• Tracking for high multiplicity
first try to measure Λ-hypernucleiup to A=52 via (e,e’K+)Λ Λ ΛΛΛ
Strangeness 2010 at KEK
ENDありがとうございました
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