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-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


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


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]


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



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


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.

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

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