CsI calibration using pi0 'sproduced by

neutron-nucleus interaction( KEK-PS E391a experiment )

S. Y. Lee Pusan National University

E391a Collaboration

High Energy Accelerator Research Organization, KEK

Faculty of Science and Engineering, Saga University

Department of Physics, Yamagata University

Department of Physics, Osaka University

Research Center for Nuclear Physics, Osaka University

National Defense Academy of Japan

Department of Physics, Ibaraki University

Joint Institute for Nuclear Research (Dubna) Russia

Department of Physics, University of Chicago

Fermi National Accelerator Laboratory

Department of Physics, Pusan National University

I. Motivation

KL Nothing

pure CsI calorimeter 4 veto

systemCALIBRATION to EM Calorimeter

II. Methodsinvariant mass of produced by neutron nucleus interaction at Al target

n

Pure CsI

Arrays

)cos(1EE2m 212

π 0

), (i 21(ADC)gE jji25j

1j

Iteration Process Do i=1, 576 for given CsI Module Reconstruct invariant mass from all 2 event ( , other)

Take mean from the invariant mass distribution

Make correction factor

ENDDO

Update gains by respectively

Iterate above process until to get correct invariant mass peak of 0

iCsI

im

)()(0

0 2

m

m

m

mc

ii

iCsI

ig ii cg

(continued)Data Sample

according to distance between Target and CsI calorimeter

3 m : ~ 1.5 M reconstructed events 7 m : ~ 1.5 M reconstructed events

III. Correction to Incident Position and Angle(by M.C.)

1. Position correction at normal incident

Before correctionBefore correction After correctionAfter correctionIncident position (cm)

Center of gravity(cm

)

Center of gravity

Incident position (cm)

2. Correction to position and angle

Before correctionBefore correction After correctionAfter correction

10

Incident position (cm)

Center of gravity (cm

)

0 1 2

3 4 5

6

X axis : incident position(cm)

Y axis : center of gravity(cm)

3. Results (position and angular correction)

Before correction After correction

0m = 5.4 MeV/c2 0m= 4.1 MeV/c2

MeV/c2MeV/c2

IV. Iteration

Before Iteration

MeV/c2MeV/c2

After Iteration

Results (Iteration)

Before Iteration

= 4.1 MeV/c2

RMS of Mass Peak of Each CsIs

= 1.05 MeV/c2

~ 480 MeV/C2

After Iteration

= 3.7 MeV/c2

RMS of Mass Peak of Each CsIs

= 0.05 MeV/C2

~ 540 MeV/C2

0m 0m

m m

Gain Change (preliminary)

Before (from muon) mean : 2.3 MeV/pC

After Iteration mean : 2.7 MeV/pC

MeV/pC MeV/pC

V. Summary We improve the precision of CsI Calibration

Position and Angular Corrections

More Correct position of Gamma

Better reconstructed pi0 mass peak( 25 % improvement of sigma )

Iteration Process Additional 10 % improvement

Update gain constant

Proper mass peak position of and

Differential Angular Correction

Incident position (cm)

cog(=

n) - co

g(=

n-1

)

)0()1( ff

)1()2( ff

Correction FactorFor given CsI module

If gain is fully calibrated,

Take the ratio

, Assume

We can get ,

iCsI

)()(0

0 2

m

m

m

mc

ii

)((ADC)g(ADC)g)(EEm ooiioii cos1cos122

)cos1cos1220 ((ADC)g(ADC)g)(EEm o

coi

ci

co

ciπ

))(()( 20

o

co

i

ci

i g

g

g

g

m

m

m

m

g

g

o

co 0

iici gcg

Basic Properties of Pure CsI

: 4.53 : 1.85 Moliere : 3.8 : 5.6 : 36.5 : 36f, 620s

: 305f, ~480s

: 1.80 light output(rel) : 0.10f, 0.20s (4k )f

)g/cm3(

(cm)X 0

)/(/ cmMeVdxdE

(cm)Ins)(

)(max nm

Dn

MeVphoton /

Mean value distribution( mass peaks of reconstructed pion mass distribution of

CsIs)

Before (from muon) RMS : 1.05 MeV/c2

After Iteration RMS : 0.5 MeV/c2

MeV/pCMeV/c2MeV/c2

3. Results-more

Before correction After correction

0m = 5.3 MeV/c2 0m= 4.1 MeV/c2

Gain Change (preliminary)