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HES HKS meeting

E05-115 experimental setup in JLab Hall C (2009). HES HKS meeting. 18 Oct 2010 T.Gogami. e , e + in HKS ? . x. e , + e -. z. HES. HKS. b.g. mix. multi. CH 2 7 Li 9 Be 10 B 12 C 52 Cr H 2 O. e +. 1 – 25 [ kHz ]. < 2 [ MHz ]. entrance of hall prove. elemag cascades.

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HES HKS meeting

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  1. E05-115 experimental setup in JLab Hall C (2009) HES HKS meeting 18 Oct 2010 T.Gogami

  2. e , e+ in HKS ? x e,+e- z HES HKS b.g. mix multi CH2 7Li 9Be 10B 12C 52Cr H2O e+ 1 – 25 [ kHz ] < 2 [ MHz ] entranceof hall prove elemag cascades Harver make these bad! x’ [rad] x [cm]

  3. Content • Positron simulation • H2O > 52Cr • Harver Foil is innocent • Origin of background Water-cell Target 5 mm 循環水

  4. Positron Simulation Setup 角度 Angular distribution Number 数

  5. Can HKS accept positrons ? positrons particles SIMULATION 2 – 12 [deg] θ definition

  6. e+ angular distribution HKS cannot accept e+ generated in target directly Shot 600M e- on the target Similar result for 52Cr , H2O target

  7. Number of e+Simulation result Momentum [MeV/c] • 12C ( 26.8 [ μA] ) • 618 [/ 600M events] • 170 [MHz] • 52Cr ( 7.6 [ μA] ) • 6022 [/ 600M events] • 477 [MHz] • H2O ( 2.7 [ μA] ) • 18511 [/ 600M events] • 521 [MHz] Momentum > 800 [MeV/c] No cut θ [mrad] • 12C ( 26.8 [ μA] ) • 8119 [/ 600M events] • 2267 [MHz] • 52Cr ( 7.6 [ μA] ) • 81224 [/ 600M events] • 6430 [MHz] • H2O ( 2.7 [ μA] ) • 239367 [/ 600M events] • (no foil ==> 239348) • 6732 [MHz] Effect of harver : <10-2 %

  8. Electromagnetic cascades electron easier to generate X0 N ∝2t 2X0 3X0 t = X0 / pass ~ X0/ thickness Radiation length 12C : 43 [g/cm2] H2O : 36 [g/cm2] 52Cr: 14 [g/cm2] 20 [cm] 36 [cm] 2 [cm] 2.5e-3 13.9e-3 8.8e-3 X0∝ 1/Z2

  9. e+ / 1 event H2O: 5 [mm] 52Cr : 170 [μm] SIMULATION

  10. ( e+ / 1 event ) * Current H2O: 5 [mm] 52Cr : 170 [μm] SIMULATION Much more positrons can be generated with H2O target than 52Cr.

  11. HKS GEANT4 Generate positrons into HKS with these regions.

  12. Background ! Region in previous slide Splitter magnet Fe : 10w × 5h ×5t [cm3] HKS Q1 HKS Q2 HKS D HKS detectors

  13. Positrons ~ 900 [MeV/c] Generate e+ in this region θ : 0.2± 0.2 [rad] p : 0.9 ± 0.02 [GeV/c] generation : spherical uniform

  14. Summary and to do • Positron Simulation • Angular distribution • positrons cannot be accepted in HKS directly. ==> hit hall prove entrance ==> background ! • Number • H2O can generate much more positrons than 52Cr because of its thickness. • Harver is innocent ! • To do • Positron simulation • Other targets <== consistency check with real data • Tracking • background rejection code

  15. End えっ、ハーバーって無罪だったんだ。

  16. backup

  17. Theta angular distribution with no cut H2O target

  18. H2O target

  19. θ vs. momentum of e+

  20. θdistribution of e+ cut : momentum > 800 MeV/c

  21. Rate of e+

  22. Multiplicity in chambers Multi-hit TDC HES layer 10 6 52Cr target CH2 target mean ~ 1 hit mean ~ 1 hit HKS 6 6 layer 52Cr target CH2 target mean ~ 6 hit mean ~ 2 hit 22nd Indian-summer school (SNP2010)

  23. E05-115 ( 2009 Aug – Nov ) Data summary Physics Data Λ Λ Λ Λ (@36μA) Λ Calibration Data 22nd Indian-summer school (SNP2010)

  24. How to come into HKS?

  25. Background !! zoom

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