JLab hypernuclear collaboration meeting/ JSPS Core to Core Seminar

 Study of elementary process in Hall-Cp(γ*,eK+)Λ/Σ0

9May2012 – 11May2012Department 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 HKSAverage 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

Fitting function :

peak background

B : Half width at half maximumC : Center value

Cross section of p(g*,K+)LPRC 73, 035202 (2006) R. Bradford, et al.

This work (Preliminary)227±12±26 nb/srQ2=0.01 (GeV/c)2

→Compared with p(g, K+)L

K+ production at small angles

TLTTLTfull )1(2 electroproduction

SL: 0.41 = 0.35 + 0.004 - 0.001 + 0.06 ( = 0.7 )

a steep

Q2 dependence ?

P. Bydzovsky’s presentation at ECT* 2011

(g*,K+)JLab Hall-A

E05-115W=1.9 GeVQ2=0.01 (GeV/c)2

2012/3/25 JPS 2012 年次大会

Contents

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

Current missing mass spectrumJLab E05-115CH2, ~ 450 [mg/cm2]~ 2.0 [μA]~ 38 [hours]

Current missing mass spectrumJLab E05-115CH2, ~ 450 [mg/cm2]~ 2.0 [μA]~ 38 [hours]

Accidental Coincidence

Quasi free Λ from 12C

The number of events of Λ and Σ0

5760　 ± 125(Integrated : -5 – 9 MeV/c2)

1579　 ± 94(Integrated : 72 – 86 MeV/c2)

ΛΣ0

JLab E05-115CH2, ~ 450 [mg/cm2]~ 2.0 [μA]~ 38 [hours]

Definition of the cross section

Solid angle of HKSAverage value

The number of VP• Including HES solid angle 

and acceptance

Momentum acceptance cut (Λ)

HES momentum region1. 0.770 – 0.9002. 0.770 – 0.8353. 0.835 – 0.900

52ΛV g.s.

~8.5 msr

Momentum acceptance cut (Σ0)

HES momentum region1. 0.770 – 0.9002. 0.770 – 0.8353. 0.835 – 0.900

52ΛV g.s.

~8.5 msr

Concerned efficiencies

Log book

Simulation

Data

Data

Data

Data

Data

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 

0.6JLab E05-115 , Q2 = 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 : 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 :

peak background

B : Half width at half maximumC : Center value

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

K+ survival Ratio after the mass square cut (CH2)

If applied these two cut at the same time(Suv. Ratio)total = (Suv. Ratio1) + (Suv. Ratio2) – 1.0

Suv. ratio1 Suv. ratio2

Cut 2Cut 1

K+ survival ratio

K+ survival ratio after AC cut (CH2)

(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

Stricter cut of AC NPE

looser cut of AC NPE

π+K+

p

π+K+

p

K+ survival ratio after WC cut (CH2)

(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

Stricter cut of WC NPE

looser cut of WC NPE

π+K+

p

π+K+

p

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

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

Definition of the cross section

εcommon ~ 0.97SIMULATION

-5

Theta and Momenta of the scattered electrons

Angular acceptance cut

θe’ > 0.05 rad

Back ground estimation

Optimal scaling factor 1.08

Black + (Green × scaling factor) = Blue

∑ (Residual   of   Black   and   Blue )2Scaling factor : 1.