HLab meeting
description
Transcript of HLab meeting
HLab meeting
10/14/08
K. Shirotori
Contents
• SksMinus status– SKS magnet trouble– Magnetic field study
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
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
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.
Simulation
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
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.
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)
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)
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)
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)
QM4F→Measured : P vs U0
Particles passing the circled region have large difference between measured andcalculated map.
Measured
QM4F
Analysis
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
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
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
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%)
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)