Λ hypernuclear spectroscopic experiment via ( e,e’K + ) at JLab
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Transcript of Λ hypernuclear spectroscopic experiment via ( e,e’K + ) at JLab
Λ hypernuclear spectroscopic experiment via (e,e’K+) at JLab
Graduate school of science , Tohoku Univ.Toshiyuki Gogami
JLab Hall-C in May 2009
Contents
• (e,e’K+) experiment• Introduction of JLab E05-115• Development for high multiplicity data
(e,e’K+) reaction experiment
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
JLab E05-115 experiment
E05-115 experimental motivation (1)
• p-shell(7He , 9Li , 10Be , 12B) Charge symmetry breaking
(CSB) ΛN-ΣN coupling
•2009 Aug – Nov @ JLab Hall-C•(e,e’K+) reaction•Target : 7Li , 9Be , 10B , 12C , 52Cr
Λ Λ Λ Λ
First try
B Λ [M
eV]
It is difficult experimentally.“ b.g. electron due to brems. ~Z∝ 2 “
A = 52
• Medium heavy (52V) s-,p-,d-,f-orbit binding energy & cross section Mass dependence of Λ single
particle energy l ・ s splitting , core configuration
mixing dΛ, fΛ –state
Λ
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
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
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 ≈ 200 [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]
Data Summary
JLab E05-115 (2009/June – 2009/Nov)
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
This talk
Λ and Σ0
Because of high multiplicity of HKS(analysis code cannot handle with high multiplicity)
~40 hours(5 shifts)
p(γ*,K+)Λ,Σ0
Analysis for high multiplicity data
KDC1
KDC2
HKS event display
Background event of HKS
HKS dipole magnet
NMR port
z [cm]
y [cm]
x [cm] KDC1
KDC2
KDC1
KDC2
9Be , 38.4 [μA]Overhead view
Background events
Events on HKS optics
Β ≈ 1e- , e+
SIMULATION
Singles rate summaryUp to ~30 [MHz]
Up to ~15 [MHz]HES
HKS
HKS trigger ~ 10[kHz]
HES trigger ~ a few[MHz]
COIN 2.0 [kHz]
Multiplicity of typical layer of chamberHES HKS
~1.13
~1.28
~2.24
~4.94
Multiplicity is high for HKS
HKS drift chamber wire configuration
Hit wires in KDC1
Overhead viewKDC1
Black : hit wires Blue : selected wiresRed : track
Black : hit wires Blue : selected wiresRed : track
CH2 52Cr
Misidentification chance in hit wires selection increase !
REAL DATA REAL DATA
low high low high
Overhead view
New tracking scheme
Good TDC
Pattern recognition
Track fit
Solve left right
Select good combination
Combination selection with TOF counters
Reduce hit wire combinations (h_tof_pre.f)
High multiplicity
• Hit wire selection with TOF• 1X & 2X • Grouping
• Pre-PID• Cherenkov detectors
Reduce hit wires to analyze
NEW
DC hit info. selection with TOF
Selective region Maximum gradient
Minimum gradient
Particle direction
Gravity
CUT~8%
~17%
Procedure in “h_dc_tofcut.f”1. Get KTOF1X & 2X hit counter information2. Make combination of 1X and 2X hit counter if those two are in
same group (grouping) 3. Determine cut conditions on KDC1 & KDC24. Select Hit wires in KDC and Reorder them
CUT
Hit wires event display (1)
• GREEN regionSelective region
• RED markersSelected hit wires
• BLACK markersRejected hit wires
Seems to work well
Particle direction
Gravity
Apply to u,v-layer
Applied to uu’ and vv’ layers , too.
Selective region determined by 1X and 2X
Convert
v v’-layer
x x’-layer
Hit wires event display (2)
• GREEN region Selective region• RED markers & lines Selected hit wires• BLACK markers & lines Rejected hit wires
v v’ u u’
x x’
v v’ u u’
x x’
KDC1 KDC2particle particle
Results of Introduction new code
Λ c.s. (CH2/H2O) issue is solved
Increased !
Increased !
CH2
52Cr
Summary and Outlook• 3rd generation exp. E05-115 at JLab Hall-C in 2009• 7
ΛHe, 9ΛLi, 10
ΛBe, 12ΛB, 52
ΛV
• Analysis for high multiplicity data– Developed new tracking codeAnalysis efficiency is improved ! (number of event)Λ cross section of H2O and CH2 are consistent
• To get better energy resolution– Fine parameter optimization– Matrix tuning
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