1. HLab meeting 10/14/08 K. Shirotori

2. Contents SksMinus status –SKS magnet trouble –Magnetic field study

3. Introduction Hypernuclear 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

4. 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 value The innermost part of the coil

5. Study Calculated 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.

6. Simulation

7. 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

8. 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.

9. 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)

10. 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) z x ● y Local coordinate (Out)

11. Calculated(QM4F) ⇒ measured : U0,V0 QM4F→QM4FQM4F→measured  Large difference P vs U0, 2 nd 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)

12. Calculated(QM4F) ⇒ calculated(QM5F) : U0,V0 QM4F→QM4FQM4F→QM5F  Large difference P vs U0, little 2 nd 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)

13. QM4F→Measured : P vs U0 Particles passing the circled region have large difference between measured and calculated map. Measured QM4F

14. Analysis

15. Analysis method To analyze E566 data : (  +,K + ) reaction data  Correlation by measured map (sksmap272a.dat)  Correlation by calculated map  Target thickness : 12 C (3.4 g/cm 2 ) (Resolution is determined by the target) To check Missing mass (binding energy) vs u0 Missing mass (binding energy) vs v0

16. Measured map (sksmap272a.dat) Before correction After correction  U0 vs MM : 1 st +2 nd polynomial correlation  V0 vs MM : 2 nd polynomial correlation ⇒ Momentum resolution : 2.8 MeV (After correction) Correction coefficients U : -0.012*U-0.01*U 2 V : +0.05*V 2

17. Calculated map (SksQM12S272AFull.dat) Correction coefficients U : -0.012*U-0.01*U 2 V : +0.05*V 2  U0 vs MM : 1 st +2 nd polynomial correlation  V0 vs MM : 2 nd polynomial correlation ⇒ Momentum resolution : 3.1 MeV (After correction) Binding energy offset : -4 MeV Before correction After correction

18. Correlation shape U0 vs MM : 1 st +2 nd polynomial correlation V0 vs MM : 2 nd polynomial correlation Correlation shapes are almost same between all maps.  BE vs u0(dx/dz) : strong 1 st +2 nd polynomial correlation (The correlation becomes larger to the inner tracks.)  BE vs v0(dy/dz) : small 2 nd polynomial correlation  Offset : less than 10 MeV (Absolute value of magnetic field : ±1%)

19. Summary Study  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 12 C 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)