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. Toshiyuki Gogami

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

Definition of the cross section Solid angle of HKS Average value The number of VP Including HES solid angle and acceptance

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

Estimation of the number of events by the fitting ~Lambda~ Number : Mean : [keV/c2] ( Delta Mean : [keV/c2] ) Width : [keV/c2] ~Sigma~ Number : Mean : [keV/c2] ( Delta Mean : [keV/c2] ) Width : [keV/c2] peakbackground B : Half width at half maximum C : Center value

Cross section of p(  ,K + )  PRC 73, (2006) R. Bradford, et al. This work (Preliminary) 227±12±26 nb/sr Q 2 =0.01 (GeV/c) 2 →Compared with p( , K + ) 

K + production at small angles electroproduction SL: 0.41 =  (  = 0.7 ) a steep Q 2 dependence ? P. Bydzovsky’s presentation at ECT* 2011 (  *,K + ) JLab Hall-A E W=1.9 GeV Q 2 =0.01 (GeV/c) /3/25 JPS 2012 年次大会

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

Current missing mass spectrum JLab E CH 2, ~ 450 [mg/cm 2 ] ~ 2.0 [μA] ~ 38 [hours]

Current missing mass spectrum JLab E CH 2, ~ 450 [mg/cm 2 ] ~ 2.0 [μA] ~ 38 [hours] Accidental Coincidence Quasi free Λ from 12 C

The number of events of Λ and Σ ± 125 (Integrated : -5 – 9 MeV/c 2 ) 1579 ± 94 (Integrated : 72 – 86 MeV/c 2 ) Λ Σ0Σ0 JLab E CH 2, ~ 450 [mg/cm 2 ] ~ 2.0 [μA] ~ 38 [hours]

Definition of the cross section Solid angle of HKS Average value The number of VP Including HES solid angle and acceptance

Momentum acceptance cut (Λ) HES momentum region – – – Λ V g.s. ~8.5 msr

Momentum acceptance cut (Σ 0 ) HES momentum region – – – Λ V g.s. ~8.5 msr

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

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 This 0.6 JLab E05-115, Q 2 = 0.01 [GeV/c] 2, W=1.93 [GeV] Kawama-san’s results

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 angle estimation 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.

Estimation of the number of events by the fitting ~Lambda~ Number : Mean : [keV/c2] ( Delta Mean : [keV/c2] ) Width : [keV/c2] ~Sigma~ Number : Mean : [keV/c2] ( Delta Mean : [keV/c2] ) Width : [keV/c2] peakbackground B : Half width at half maximum C : Center value

Cut conditions to make the missing mass Cut conditions – 1.0 > NWC 1+2 – 5.0 < AC – -1.0 < coincidence time < 1.0 – 0.08 < Mass square < 0.44 – HKS tracking chi-square < – HES tracking chi-square < 150.0

K + survival Ratio after the mass square cut (CH 2 ) 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 K + survival ratio

K + survival ratio after AC cut (CH 2 ) (accut,wccut) = (5,-0.1) pi suv. ratio: K suv. ratio: p suv. ratio: (accut,wccut) = (10,-0.1) pi suv. ratio: K suv. ratio: p suv. ratio: (accut,wccut) = (15,-0.1) pi suv. ratio: K suv. ratio: p suv. ratio: Stricter cut of AC NPE looser cut of AC NPE π+π+ K+K+ p π+π+ K+K+ p

K + survival ratio after WC cut (CH 2 ) (accut,wccut) = (2000,1.1) pi suv. ratio: K suv. ratio: p suv. ratio: (accut,wccut) = (2000,1) pi suv. ratio: K suv. ratio: p suv. ratio: (accut,wccut) = (2000,0.9) pi suv. ratio: K suv. ratio: p suv. ratio: Stricter cut of WC NPE looser cut of WC NPE π+π+ K+K+ p π+π+ K+K+ p

Tracking efficiencies ~~~~ HKS~~~~~~~ ch2 : Tracking Efficiency : ( %) h2o : Tracking Efficiency : ( %) li : Tracking Efficiency : ( %) be : Tracking Efficiency : ( %) b : Tracking Efficiency : ( %) c : Tracking Efficiency : ( %) cr1 : Tracking Efficiency : ( %) cr2 : Tracking Efficiency : ( % ) ~~~~ HES~~~~~~~ ch2 : Tracking Efficiency : ( %) h2o : Tracking Efficiency : ( %) li : Tracking Efficiency : ( %) be : Tracking Efficiency : ( %) b : Tracking Efficiency : ( %) c : Tracking Efficiency : ( %) cr1 : Tracking Efficiency : ( %) cr2 : Tracking Efficiency : ( %) 1 ….!? Need to check tracking code

HKS efficiency ε HKS = – AC : ( ) – WC : ( ) – Tracking : (+0.001, ) – M2 : 0.96 – Ctime : 0.99 – f decay : (± 0.006) – f burn : 0.82

Definition of the cross section SIMULATION

Theta and Momenta of the scattered electrons

Angular acceptance cut θ e’ > 0.05 rad

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