1. Performance of Shower Maximum Detectors Saori Itoh (Shinshu Univ.) GLC calorimeter group (KEK,Kobe,Konan,Niigata,Shinshu,Tsukuba) Introduction Detector construction Results of beam tests

2. Shower Maximum (ShMax) detector (in the tile/fiber electromagnetic calorimeter) HCAL Tile/fiber EMCAL Pre-Shower 4.3 X 0 A tower of calorimeter ShMax placed near the EM shower maximum 1cm 4cm

3. 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 (GLC Project Report, 2003)

4. Structure of ShMax detector 20cm 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)

5. Center position of EM shower Position of strip (Xi) Energy deposit (Ei) 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

6. APD beam Two types of ShMax detectors MAPMT type Through an embeded WLS fiber, lights are read out by Multi-anode PMTs. APD (Avalanche Photodiode) type APDs are directly attached at each side of strip. We can operate at room temperature. HPK S8664-55 Active area 5mmx5mm beam 1 layer2 layers

7. APD type MAPMT type MAPMT WLS fiber APD 2 layers 1 layer

8. 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 counter C : Cherenkov counter DC : Drift chamber This shows the detector set up of beam tests. From the data of beam tests, we analyze

9. Position resolution MAPMT WLS fiber 1 2 3 4 GeV incident beam energy cm 0.3 1 Shower position – using DC position Shower position cm 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 Position resolution cm

10. Position resolution APD cm Shower position cm 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 Position resolution 1 2 3 4 GeV incident beam energy using DC position Shower position – using DC position cm

11. e/pi separation MAPMT WLS fiber Energy deposit >20mips e-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 acceptance electrons pions Cut value

12. e/pi separation APD Energy deposit > 8.5mips e-acceptance: 85% pi-rejection: 22 = 1/4.5% The normalized distribution of energy deposit of pions and electrons (1 layer) Cut value mips electrons pions acceptance 2GeV electrons pions

13. 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 resolutions. We can separate electrons from pions. e-acceptance: 85% pi-rejection: 22 ~ 24

14. 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.

15. Position dependence of strip direction mips 2GeV pi Read out APD Differences One side : 40% Both sides : 14%(pions) : 8%(electrons) (cm) 0.5 1 10 mips Position mips