hlab meeting 10/14/08 k. shirotori. contents sksminus status –sks magnet trouble –magnetic field...
TRANSCRIPT
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HLab meeting
10/14/08
K. Shirotori
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Contents
• SksMinus status– SKS magnet trouble– Magnetic field study
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IntroductionHypernuclear production via the (K-,-) and (+,K+) reaction
⇒Scattered - and K+ are analyzed by the magnetic spectrometer, using SKS.
Analysis method : Runge-Kutta calculation from the position of drift chambers and the precisely measured magnetic field map
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SKS magnet problem
One of the SKS magnet coil was broken by the high voltage test.
(It cannot be repaired… )
Effects to experiments• Strength of filed : 5/6 (2.7
T 2.5 T @ 395A)⇒⇒Decreasing acceptance and
momentum resolution• Change of filed shape⇒Tracking and absolute
momentum valueThe innermost part of the coil
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StudyCalculated field maps are compared with the measured map.
Simulation• Scattered particles tracks generated with
calculated maps (as a true magnetic filed) are analyzed by the measured map or calculated map.
Real data analysis• Real experimental data (KEK E566 data) are
analyzed by calculated maps.
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Simulation
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Simulated conditions
Particles generation in the simulation• - of 1.4 GeV/c with uniform scattering
angular distribution up to 20 degree • No multiple scattering
Analysis of simulated data• Tracking by using the hit positions of
drift chamber• Drift chamber resolution ~400 m
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Magnetic field map
sksmap395a.dat (measured,) Measured 395A magnetic field map
SksQM4S395AFullC.dat (QM4F) Calculated field map Full coil version
SksQM5S395AFullC.dat (QM5F) Calculated field map Full coil version Different B-H curve from QM4F
QM4 Fis used as generated map in the simulation.
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Field map and particle tracks
Particles pass the incomplete magnetic filed map region, but they are rejected and there are no large effects.
Measured
Calculated(QM4)
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Meaning of observables
P : Momentum U0 : angel (dx/dz) of
production point V0 : angle (dy/dz) of
production point
(x,y,z belong local coordinate)
z
x
● y
Local coordinate (In)zx
●
y
Local coordinate (Out)
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Calculated(QM4F) measured : U0,V0⇒QM4F→QM4F QM4F→measured
Large difference P vs U0, 2nd polynomial shape P vs V0, tracks near the SKS magnet coil gap
Momentum resolution : 1.7 MeV/c 2.4 MeV/c (to select good region)⇒ Tracking 2~1.6 (1.0 original)
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Calculated(QM4F) calculated(QM5F) : U0,V0⇒QM4F→QM4F QM4F→QM5F
Large difference P vs U0, little 2nd polynomial shape P vs V0, almost flat
Momentum resolution : 1.7 MeV/c 2.3 MeV/c (no correction)⇒ Tracking 2~1.0 (1.0 original)
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QM4F→Measured : P vs U0
Particles passing the circled region have large difference between measured andcalculated map.
Measured
QM4F
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Analysis
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Analysis method
To analyze E566 data : (+,K+) reaction data Correlation by measured map (sksmap272a.d
at) Correlation by calculated map Target thickness : 12C (3.4 g/cm2)(Resolution is determined by the target)
To checkMissing mass (binding energy) vs u0Missing mass (binding energy) vs v0
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Measured map (sksmap272a.dat)Before correction After correction
U0 vs MM : 1st+2nd polynomial correlation V0 vs MM : 2nd polynomial correlation⇒Momentum resolution : 2.8 MeV (After correction)
Correction coefficientsU : -0.012*U-0.01*U2
V : +0.05*V2
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Calculated map (SksQM12S272AFull.dat)
Correction coefficientsU : -0.012*U-0.01*U2
V : +0.05*V2
U0 vs MM : 1st+2nd polynomial correlation V0 vs MM : 2nd polynomial correlation⇒Momentum resolution : 3.1 MeV (After correction)Binding energy offset : -4 MeV
Before correction After correction
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Correlation shape
U0 vs MM : 1st+2nd polynomial correlation
V0 vs MM : 2nd polynomial correlation
Correlation shapes are almost same between all maps. BE vs u0(dx/dz) : strong 1st+2nd polynomial correlation (The
correlation becomes larger to the inner tracks.) BE vs v0(dy/dz) : small 2nd polynomial correlation Offset : less than 10 MeV (Absolute value of magnetic field : ±1%)
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SummaryStudy Simulation
Generated by calculated map Analyzed by measured or ⇒calculated map
Check the correlation between momentum and scattering angle⇒To check the difference of absolute values and angles
Real data analysis @ 272A map E566 thin 12C target data analyzed by measured or calculated map Check the correlation between binding energy and scattering
angle ⇒ Correlation shapes are almost same between all maps. ⇒ The correlation can be corrected.
For the experiments High resolution experiments
To correct the correlation by many binding energy data How to determine the absolute value ?
Coincidence experiment (Hypernuclear -ray spectroscopy, weak decay)
The correction is almost enough to select the binding state. (Momentum resolution is not need to be so high)