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9May2012 – 11May2012 Department of Physics, Graduate School of Science, Tohoku Univ.

JLab hypernuclear collaboration meeting / JSPS Core to Core Seminar  Study of elementary process in Hall-C p(γ*, eK + )Λ/Σ 0. 9May2012 – 11May2012 Department of Physics, Graduate School of Science, Tohoku Univ. Toshi yuki Gogami. Contents. Kawama-san’s results

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9May2012 – 11May2012 Department of Physics, Graduate School of Science, Tohoku Univ.

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  1. JLab hypernuclear collaboration meeting/ JSPS Core to Core Seminar Study of elementary process in Hall-Cp(γ*,eK+)Λ/Σ0 9May2012 – 11May2012 Department of Physics, Graduate School of Science, Tohoku Univ. Toshiyuki Gogami

  2. Contents • Kawama-san’s results • Derive the cross section by myself

  3. Definition of the cross section • The number of VP • Including HES solid angleand acceptance • Solid angle of HKS • Average value

  4. Contents • Kawama-san’s results • Derive the cross section by myself

  5. Estimation of the number of events by the fitting  ~Lambda~     Number : 6402.57     Mean   : 28.5527 +- 19.7152 [keV/c2]     ( Delta Mean : 28.5527 +- 19.7152 [keV/c2] )     Width  : 1937.59 +- 52.1221 [keV/c2]  ~Sigma~     Number : 1688.07     Mean   : 76809.3 +- 42.7735 [keV/c2]     ( Delta Mean : -149.659 +- 42.7735 [keV/c2] )     Width  : 1848.15 +- 121.343 [keV/c2] Fitting function : B : Half width at half maximum C : Center value peak background

  6. Cross section of p(g*,K+)L PRC 73, 035202 (2006) R. Bradford, et al. →Compared with p(g, K+)L This work (Preliminary) 227±12±26 nb/sr Q2=0.01 (GeV/c)2

  7. P. Bydzovsky’s presentation at ECT* 2011 K+ production at small angles electroproduction SL: 0.41 = 0.35 + 0.004 - 0.001 + 0.06 ( e = 0.7 ) a steep Q2 dependence ? (g*,K+) JLab Hall-A E05-115 W=1.9 GeV Q2=0.01 (GeV/c)2 JPS 2012年次大会

  8. Contents • Kawama-san’s results • Derive the cross section by myself

  9. Current missing mass spectrum JLab E05-115 CH2, ~ 450 [mg/cm2] ~ 2.0 [μA] ~ 38 [hours]

  10. Current missing mass spectrum JLab E05-115 CH2, ~ 450 [mg/cm2] ~ 2.0 [μA] ~ 38 [hours] Quasi free Λ from 12C Accidental Coincidence

  11. The number of events of Λ and Σ0 JLab E05-115 CH2, ~ 450 [mg/cm2] ~ 2.0 [μA] ~ 38 [hours] Λ Σ0 5760± 125 (Integrated : -5 – 9 MeV/c2) 1579± 94 (Integrated : 72 – 86 MeV/c2)

  12. Definition of the cross section • The number of VP • Including HES solid angleand acceptance • Solid angle of HKS • Average value

  13. Momentum acceptance cut (Λ) ~8.5 msr HES momentum region • 0.770 – 0.900 • 0.770 – 0.835 • 0.835 – 0.900 52ΛV g.s.

  14. Momentum acceptance cut (Σ0) ~8.5 msr HES momentum region • 0.770 – 0.900 • 0.770 – 0.835 • 0.835 – 0.900 52ΛV g.s.

  15. Concerned efficiencies Log book Data Data Data Data Data Simulation Data Data (E01-011)

  16. Preliminary results Notice that several cuts are applied for HKS  Solid angle should be less than ~8.5 msr Cross section is going to be larger JLab E05-115 , Q2 = 0.01 [GeV/c]2 , W=1.93 [GeV] 0.6 Kawama-san’s results This

  17. Summary and Outlook • Summary • The elementary cross sections is similar to the results of p(γ,K+)Λ from CLAS and SAPHIRE • Outlook • VP flux • Precise solid angleestimation of HKS (and HES) • Depending on Momenta and angles • Efficiencies • Tracking, Trigger, PID cut • Effective target thickness • Burned effect  Compare to the other experiments (Hall-A, CLAS, SAPHRE) and theories.

  18. Estimation of the number of events by the fitting  ~Lambda~     Number : 6402.57     Mean   : 28.5527 +- 19.7152 [keV/c2]     ( Delta Mean : 28.5527 +- 19.7152 [keV/c2] )     Width  : 1937.59 +- 52.1221 [keV/c2]  ~Sigma~     Number : 1688.07     Mean   : 76809.3 +- 42.7735 [keV/c2]     ( Delta Mean : -149.659 +- 42.7735 [keV/c2] )     Width  : 1848.15 +- 121.343 [keV/c2] Fitting function : B : Half width at half maximum C : Center value peak background

  19. Cut conditions to make the missing mass • Cut conditions • 1.0 > NWC1+2 • 5.0 < AC1+2+3 • -1.0 < coincidence time + 54.9 < 1.0 • 0.08 < Mass square < 0.44 • HKS tracking chi-square < 150.0 • HES tracking chi-square < 150.0

  20. K+ survival Ratio after the mass square cut (CH2) K+ survival ratio If applied these two cut at the same time (Suv. Ratio)total = (Suv. Ratio1) + (Suv. Ratio2) – 1.0 Suv. ratio1 Suv. ratio2 Cut 2 Cut 1

  21. K+ survival ratio after AC cut (CH2) looser cut of AC NPE (accut,wccut) = (5,-0.1)pi suv. ratio: 0.0631439+-0.00148976K  suv. ratio: 0.876875+-0.00513167p  suv. ratio: 0.911427+-0.0023794(accut,wccut) = (10,-0.1)pi suv. ratio: 0.105762+-0.0019663K  suv. ratio: 0.931211+-0.00536427p  suv. ratio: 0.94023+-0.00243485(accut,wccut) = (15,-0.1)pi suv. ratio: 0.141455+-0.00231043K  suv. ratio: 0.956913+-0.00547386p  suv. ratio: 0.960014+-0.00247285 p K+ π+ Stricter cut of AC NPE p K+ π+

  22. K+ survival ratio after WC cut (CH2) looser cut of WC NPE (accut,wccut) = (2000,1.1)pi suv. ratio: 0.922368+-0.00752531K  suv. ratio: 0.987653+-0.00566791p  suv. ratio: 0.133889+-0.000701787(accut,wccut) = (2000,1)pi suv. ratio: 0.963952+-0.00777583K  suv. ratio: 0.989093+-0.0056741p  suv. ratio: 0.176933+-0.000821917(accut,wccut) = (2000,0.9)pi suv. ratio: 0.971601+-0.00782181K  suv. ratio: 0.999575+-0.00571909p  suv. ratio: 0.259314+-0.00102927 p K+ π+ Stricter cut of WC NPE K+ p π+

  23. Tracking efficiencies • ~~~~ HKS~~~~~~~ch2 : Tracking Efficiency : 0.998974 +- 0.00760814 (0.761596%)h2o : Tracking Efficiency : 0.961109 +- 0.00190445 (0.198152%)li : Tracking Efficiency : 0.996378 +- 0.0205954 (2.06703%)be : Tracking Efficiency : 0.995274 +- 0.00535923 (0.538468%)b : Tracking Efficiency : 0.99921 +- 0.00912634 (0.913356%)c : Tracking Efficiency : 0.987929 +- 0.00179032 (0.181219%)cr1 : Tracking Efficiency : 0.974892 +- 0.00304261 (0.312097%)cr2 : Tracking Efficiency : 0.965851 +- 0.00320905 (0.332251% ) • ~~~~ HES~~~~~~~ch2 : Tracking Efficiency : 1 +- 0.00527844 (0.527844%)h2o : Tracking Efficiency : 1 +- 0.00095474 (0.095474%)li : Tracking Efficiency : 1 +- 0.0172701 (1.72701%)be : Tracking Efficiency : 1 +- 0.00419163 (0.419163%)b : Tracking Efficiency : 1 +- 0.00820523 (0.820523%)c : Tracking Efficiency : 1 +- 0.00153384 (0.153384%)cr1 : Tracking Efficiency : 1 +- 0.00100727 (0.100727%)cr2 : Tracking Efficiency : 1 +- 0.00103985 (0.103985%) 1 ….!? Need to check tracking code

  24. HKS efficiency • εHKS = 0.169 • AC : 0.877 (+-0.005) • WC : 0.990 (+-0.006) • Tracking : 0.999 (+0.001, - 0.007) • M2 : 0.96 • Ctime : 0.99 • fdecay : 0.252 (± 0.006) • fburn : 0.82

  25. Definition of the cross section εcommon ~ 0.97 -5 SIMULATION

  26. Theta and Momenta of the scattered electrons

  27. Angular acceptance cut θe’ > 0.05 rad

  28. Back ground estimation Optimal scaling factor  1.08 Scaling factor : 1. Black + (Green × scaling factor) = Blue

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