Performance ofShower Maximum Detectors

Saori Itoh (Shinshu Univ.)

GLC calorimeter group

(KEK,Kobe,Konan,Niigata,Shinshu,Tsukuba)

• Introduction• Detector construction• Results of beam tests

Shower Maximum (ShMax) detector (in the tile/fiber electromagnetic calorimeter)

HCAL

Tile/fiber EMCAL

Pre-Shower 4.3 X0

A tower of calorimeter

ShMaxplaced near the EM shower maximum

1cm

4cm

4cm

ShMax detector (in the tile/fiber electromagnetic calorimeter)

• Precise measurements of the incident positions of electrons and photons

• Electron/hadron separation

The requirement of position resolution is

Emm /3 (GLC Project Report, 2003)

Structure of ShMax detector

20cm

20c

m

y

x

20strips x 2 layers

z We use scintillator strips for ShMax detector.

A layer of ShMax detector consists of 20 scintillator strips.

We can measure energy deposit and determine the center position of EM shower.

We can measure the 2 dimensional position using 2 layers.

A strip size (1cmx1cmx20cm)

Center position of EM shower

ii

ii

i

E

ExCenter position of EM shower

Position of strip (Xi)

En

erg

y d

ep

osit

(E

i)

4GeV e

This shows energy deposit of each strip (Ei) as a function of strip position (Xi) for a 4GeV electron.

Using weighted mean, we can determine the center position of EM shower.

mips

strip number

APD APD

beam

Two types of ShMax detectorsMAPMT typeThrough an embeded WLS fiber, lights are read out byMulti-anode PMTs.

APD(Avalanche Photodiode) typeAPDs are directly attached at each side of strip. We can operate at room temperature.

HPK S8664-55Active area 5mmx5mm

beam

1 layer2 layers

APD typeMAPMT type

MAPMT

WLS fiber

APDAPD

2 layers 1 layer

Beam test @KEK 1-4GeV mixed beam

Pre-Shower(Pb 4mm+Scintillator 1mm) x 6 layers

• Position resolution• Electron/pion separation capability

T C C DC DC T ShMax

EMCAL

T : Trigger counterC : Cherenkov counterDC : Drift chamber

This shows the detector set up of beam tests.

From the data of beam tests, we analyze

Position resolutionMAPMT

WLS fiber

1 2 3 4 GeV incident beam energy

cm

0.3

1

Shower position – using DC position

Sh

ower

pos

itio

n c

m

using DC position

3.7mm

The correlation of the shower position of ShMax and the extrapolated position from DC

The distribution of their differences

The sigma gives position resolution

Position resolution as a function of the incident beam energy

4GeV e

Pos

ition

res

olut

ion

cm

cm

Position resolutionAPDAPD

cm

Sh

ower

pos

itio

n c

m

1

0.3 3.4mm

Position resolution as a function of the incident beam energy

The correlation of the shower position of ShMax and the extrapolated position from DC

The distribution of their differences

The sigma gives position resolution

4GeV e

Pos

ition

res

olut

ion

1 2 3 4 GeV incident beam energy

using DC position

Shower position – using DC position

cm

cm

e/pi separationMAPMT

WLS fiber

Energy deposit >20mipse-acceptance: 85%pi-rejection: 24 = 1/4.1%

The normalized distribution of energy deposit of pions and electrons (Sum of 2 layers)

energy deposit mips

acc

ept

anc

e

electrons

pions

Cut value

e/pi separation

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25

APDAPD

Energy deposit > 8.5mipse-acceptance: 85%pi-rejection: 22 = 1/4.5%

The normalized distribution of energy deposit of pions and electrons (1 layer)

Cut value mips

electrons

pionsa

cce

pta

nce

2GeV

electrons

pions

Summary

• We tested two types of ShMax detectors.

• Position resolutions are about the same.

3.4mm ~ 3.7mm at 4GeV Without a gap, we can get better position resolu

tions.

• We can separate electrons from pions.

e-acceptance: 85%

pi-rejection: 22 ~ 24

Summary (cont’d.)

• Our R&D of ShMax detector will help for the new calorimeter model ( SiPM type ) with fine granularity.

• We need simulation to know the best segmentation of strip-array detectors.