spectroscopic investigation of p-shell Λ hypernuclei by the (e,e'k + ) reaction - analysis...
TRANSCRIPT
Spectroscopic Investigation of P-shell Λ
hypernuclei by the (e,e'K+) Reaction
-Analysis Update of the Jlab Experiment
E05115-
Chunhua ChenHampton Universithy
Outline
Experimental Goal of E05115
Kinematics of the E05115
Experimental Setup of E05115
System calibration procedure and status
Preliminary results
Summary and to do
Experimental GoalThe 3rd Generation Hypernuclear Spectroscopy in JLab-HallC
Spectroscopy of Medium - heavy hypernucleus
52Cr(e,e’K+) 52LV
L single particle nature in the mean field
quark picture vs. conventional pictureSpectroscopy of Light L hypernuclei
LN interactions, ls splitting, Charge Symmetry Breaking
p shell hypernuclei : 12C(e,e'K+)12ΛB , 7Li(e,e'K+)7
ΛHe, 10B(e,e'K+)10ΛBe ,
and 9Be(e'K+)9ΛLi
Calibration by the elementary process p(e,e’K+)Λ or Σ: H2O and CH2
Kinematics of the E05-115 Experiment
+p →+K+
Momentum: 2.344GeV/c
Momentum: 0.844GeV/c ±17%Angular acceptance: 3°〜 9°
Momentum: 1.2GeV/c ±12.5%
Angular acceptance : 1°〜 13°
1.5GeV γ*
Scattered electron
K+
Electron beam
Target nucleus
pCoincidence
measurement
Experimental Setup
Splitter Magnet
HKS
HES
PreChicane-SPL-(HKS+HES) Configuration
Experimental Setup -Detector Package-
HES-D
e’
EHOD2
EHOD1
EDC2EDC1
HES Detectors
Calibration Procedure of the Spectrometer System
Forward Tuning
Backward tuning
mass spectroscopy
Nonlinear Least Chi2 fitting
Kinematical scan
Initial state
Magnetic field study
Geant4 Simulation Focal plane pattern
Real Data
Λ & Σ mass spectroscopy
Field map
Focal plane pattern
Matching level A
SS pattern SS hole
Matching level
B
Kinematical parameters
Independent level C
matrices
A&B&C
Forward Optics Tuning
Purple: Real HKS SS data Blue: Geant4 Simulation Splitter field contour on xoz plane
The leakage of splitter fringe field causes the cross talk between the splitter and quadrupoles
Purple: Geant4 simulation green: Real HES SS data
Target
Beam Kaon
Q1
Q2
Forward Optics Tuning
The asymmetry functions are introduced and tuned for HKS&HES quadruple field Bx and By, independently.
The Mass Status of Forward Optics Tuning
Start Point
after forward tuning 11
Backward Calibration Procedure
= = (Ebeam , Pk , xt’k, yt’k , Pe, , xt’e, ,yt’e’ )
(1+δ/100)
Nonlinear least 2 fitting
ΔEbeam0
optimization
Kinematical Calibration
Optical Calibration
MomentumMatrix
AngleMatrix
ΔPK,ΔPe optimization
Beam Energy Scan
iterate
iterate
+
𝜒22=𝜔 Λ (𝜎 Λ
𝑓𝑖𝑡 )2/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎Σ
𝑓𝑖𝑡 )2/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠
𝑓𝑖𝑡 )2/¿𝜎𝑔𝑠>¿2 ¿¿¿¿
gs : 12ΛBgs
Start Point
Fitting Function:Cauchy+pol3
Particle Mean(MeV) FWHM
Λ 0.4495 2.832
Σ0 76.74 3.27
σ~2.7MeV
H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c
FWHM~2.6MeV
Preliminary Status
#1
#2
Peak# Mean(MeV) σ (MeV)
1 -11.39 0.367
2 -0.40 ~1.8
FWHM~1.675MeV
FWHM~1.775MeV
FWHM~1.565MeV
FWHM~2.0MeV
Preliminary Result 7ΛHe
E01011 data
E. Hiyama, et al., PRC53 2078 (1996)
n
n
6He core3/2+&5/2+
Preliminary Result 10ΛBe – 10
ΛBe
3/2-0.00
5.59 3/2-
7/2-6.38
5/2-7.94
2.43 5/2-1/2-2.78
1/2+1.68
5/2+3.04
3/2+4.70
9/2+6.76
Low Lying 9Be Level Structure
1-2-
(< 0.1)10
Be
Missing mass status – 9LLi
Hall A Result(To be published soon)
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Summary and to do
By current calibration method, we are able to get clear
mass spectroscopy , which is not included in the calibration
data set;
Current resolution is still factor of 2 away from expected
resolution, the iteration will continue to improve the
optical matrices as well as the kinematics;
Other issue: High multiplicity tracking problem for heavy
target data.
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Back up
New Data Sets
All carbon runs with clear beam current and
nominal beam energy.There are around 414 events in peak #1, and the S/N is around 2.35.
#1
The improvement of the resolution is small with the old
data, since the statistic of 12ΛBgs is small, which is
momentum sensitive .
ProblemSince the improvement of the resolution still small, increase the weight of 12
ΛBgs by factor of 4 on the base of the statistical weight .
7ΛHe Missing Mass
σ ~ 1.0 MeV
Target Straggling
σ~3.2MeV
First turn of optics tune with CH2 Data
1. There is still kinematical parameters dependence of Λ and Σ
(1-2MeV) after forward optical tuning;
2. Counts of 12ΛB from low luminosity data is small, and also its
resolution is bad, the S/N ratio of selected region is small;
σ~2.7MeV
Tune Angle matrix and momentum
matrix at same time
Preliminary Status -7
ΛHe-
E01011 data
Resolution : ~510 keV (FWHM) for g.s.Data taking : ~30 hours w/ 30 mA
Peak # Mean(MeV) σ (MeV)
1 -5.46 0.549
2 -3.94 4.66
Theoretical calculation Binding energy: Hiyama w/o CSB
1/2+ (-BΛ=-5.37)
#1#2
First turn optics tune with CH2 Data
Particle Mean(MeV) FWHM
Λ 0.2098 2.122
Σ0 77.41 2.456
First turn optics tune with CH2 Data
FWHM~2.9MeV
H2O target
FWHM~2.6MeV
H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c
First turn optics tune with CH2 Data
FWHM~2.9MeV
H2O target
FWHM~2.6MeV
H2O target Beam Momentum: 2.344GeV/c + 20 MeV/c
Target Mass Events # above BG S/N
CH2 Λ 9976 3.54
Σ0 2650 1.40
H2O(Pe~2.364) Λ 283 2.96
C12 (BC=20uA) 309 1.61
Data sets
e , e+ background in GEANT simulation
Vacuum chamber(sus304)
NMR port(sus304)
KDC1 KDC2
e- , e+
Generated particle : e+
Distribution : spherical uniform Momentum : 860 – 1000 [MeV/c] Angle : 0 – 2 [mrad] 1000 events
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e+
HKS
Calibration procedure-Beam Energy Scan-
𝜒12=𝜔 Λ(𝑚 Λ
𝑓𝑖𝑡−𝑚Λ0 )/𝜎 Λ
2+¿𝜔Σ(𝑚Σ𝑓𝑖𝑡−𝑚Σ
0 )/𝜎 Σ2 ¿
𝜒22=𝜔 Λ(𝜎 Λ
𝑓𝑖𝑡)/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎 Σ
𝑓𝑖𝑡)/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠
𝑓𝑖𝑡) /¿𝜎𝑔𝑠>¿2 ¿¿¿¿
ωi:statistic weigth
Coincident
Time: The correlation of HKS target time and HES target time, give us the coincident spectrum:
Real events
Accidental
Ktar
etarcoin TTT '
PID cut is applied and path length has been done
Coincident Trigger Set
HKS :
HKStrigger=(CP)×(K)
CP=(KTOF1X)×(KTOF1Y)×(KTOF2X)
K=WC×
HES:
HEStrigger=(EHODO1)×(EHODO2)
×:AND
COINtrigger=(HKStrigger)×(HEStrigger)
Kinematics of the E05-115 Experiment
Momentum: 2.344GeV/c
Momentum: 0.844GeV/c ±17%Angular acceptance: 3°〜 9°
Momentum: 1.2GeV/c ±12.5%
Angular acceptance : 1°〜 13°
1.5GeV γ*
Scattered electron
K+
Electron beam
M.Q.Tran et al. PLB445 (1998) 20
+p →+K+
Target nucleus
pCoincidence
measurement
Preliminary Status
#1
#2
Peak# Mean(MeV) σ (MeV)
1 -11.39 0.367
2 -0.40 ~1.8
FWHM~1.675MeV
FWHM~1.775MeV
FWHM~1.565MeV
FWHM~2.0MeV
#1 #2
FWHM~1.675MeV
FWHM~1.565MeV
Spectrometer System Calibration-Minimize -
Kinematics calibration: utilizing well known masses of , produced from CH2 , 12
ΛBgs from 12C to determine binding energy to a level of precision ~100keV
Optical calibration: Minimize Chisquare w.r.t reconstruction matrix M by an Nonlinear Least Square method.
Mgs: fitted meanMΛ &MΣ : theoretical dataωi : statistic weigth
𝜒12=𝜔 Λ(𝑚 Λ
𝑓𝑖𝑡−𝑚Λ0 )/𝜎 Λ
2+¿𝜔Σ(𝑚Σ𝑓𝑖𝑡−𝑚Σ
0 )/𝜎 Σ2 ¿
𝜒22=𝜔 Λ(𝜎 Λ
𝑓𝑖𝑡)/¿𝜎 Λ>¿2+¿𝜔Σ (𝜎 Σ
𝑓𝑖𝑡)/¿𝜎 Σ>¿2+𝜔𝑔𝑠(𝜎 𝑔𝑠
𝑓𝑖𝑡) /¿𝜎𝑔𝑠>¿2 ¿¿¿¿
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PreChicane-SPL-(HKS+HES) Configuration
Calibration Data Set
Target CH2 12C H2O
Mass Λ Σ Λ12B Λ
Beam P(MeV/c) ~2.344 ~2.344 2.364
Beam Current(uA) ~2 ~20 ~3.5
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Mass spectroscopy ofΛ,Σ and 12
ΛB(mean and peak
width)