Performance of Shower Maximum Detectors

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

2. 4cm ShMax placed near the EM shower maximum 1cm Shower Maximum (ShMax) detector (in the tile/fiber electromagnetic calorimeter) Tile/fiber EMCAL 4cm Pre-Shower 4.3 X0 A tower of calorimeter HCAL

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 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. z 20cm y x 20strips x 2 layers A strip size (1cmx1cmx20cm)

5. Center position of EM shower 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 Center position of EM shower 4GeV e Energy deposit (Ei) strip number Position of strip (Xi)

6. beam APD APD 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. 2 layers 1 layer beam HPK S8664-55 Active area 5mmx5mm

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

8. Beam test@KEK 1-4GeV mixed beam This shows the detector set up of beam tests. ShMax T C C DC DC T EMCAL T : Trigger counter C : Cherenkov counter DC : Drift chamber Pre-Shower (Pb 4mm+Scintillator 1mm) x 6 layers From the data of beam tests, we analyze • Position resolution • Electron/pion separation capability

9. Position resolution WLS fiber MAPMT The correlation of the shower position of ShMax and the extrapolated position from DC 4GeV e Position resolution as a function of the incident beam energy Shower position cm cm 1 cm Position resolution using DC position The distribution of their differences The sigma gives position resolution 0.3 3.7mm 1 2 3 4 GeV incident beam energy cm Shower position – using DC position

10. Position resolution APD APD The correlation of the shower position of ShMax and the extrapolated position from DC 4GeV e Position resolution as a function of the incident beam energy Shower position cm cm 1 cm using DC position Position resolution The distribution of their differences The sigma gives position resolution 3.4mm 0.3 cm 1 2 3 4 GeV incident beam energy Shower position – using DC position

11. e/pi separation WLS fiber MAPMT 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) electrons acceptance pions energy deposit mips Cut value

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

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. 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. Summary(cont’d.)