Performance of Scintillator-Strip Electromagnetic Calorimeter for the ILC experiment Satoru Uozumi (Kobe University) for the CALICE collaboration Mar 12 th -17 th EPOCHAL Tsukuba - Contents - ILC and PFA Scintillator-ECAL concept Study of elementary components Performance of test module

Jet Energy Measurement at the ILC experiment Separation of jet particles in the calorimeter is required for the PFA  Fine granular calorimeter is necessary. Particle Flow Algorithm (PFA) allows precise jet-energy measurement. Various precision measurements expected: – e + e -  H, W, Z, tt, SUSY, etc …  Multi-jets final states. E jet = p e + p  + p charged hadron + E  + E neutral hadron [ tracks only] [calorimeter only]

281 physicists/engineers from 47 institutes and 12 countries coming from 3 regions (America, Asia and Europe) CAlorimeter for the LInear Collider Experiment Main Task : Develop fine granular calorimeter for Particle Flow Algorithm at the ILC experiment. Electromagnetic CAL: Scintillator-Tungsten (Kobe / Shinshu / Tsukuba / Niigata / Tokyo / Kyungpook universities) Silicon-Tungsten Digital SiW ECAL (MAPS) Hadron CAL: Analog (Scintillator) HCAL Digital HCAL

The Scintillator-Strip Electromagnetic Calorimeter Scintillator strip (4.5 x 1 x 0.2 cm) MPPC WLS fiber Sampling calorimeter with Tungsten- scintillator sandwich structure. Scintillator strip technology adopted to achieve fine granularity. Huge Number of channels (~10M for ECAL, ~4M for HCAL). Need to solve many challenging issues Establish the components while keeping low production costs Stability & Robustness First need to establish the feasibility!

Scintillator strip by extrusion technique Multi-Pixel Photon Counter Absolute amount of light Response uniformity Effect of covering material Transparency Mechanical stability Production cost Study of the Elementary Components (Scintillator-Strip + Photo-Sensor) Performance (gain, QE) comparable to normal photomultiplier Low dark noise Low cost Wavelength Shifting Fiber (Y11) High absorption and re-emission efficiency

Consists of Geiger-mode APD pixel matrix. High Gain (10 5 ~10 6 ) Enough Photon Detection Efficiency (~15% with 1600 pixel) Compact (package size ~ a few mm) Low Cost Insensitive to magnetic field Dark noise exists ( ~100 kHz) Input vs output is non-linear ~ 1 mm Substrate Development of the Multi-Pixel Photon Counter (MPPC) - a novel semiconductor photo-sensor - We are developing and studying the MPPC with Hamamatsu Photonics / KEKDTP group. Reasonably good performance has been achieved so far for Sci-Strip readout. (-> see Y. Sudo’s poster) 1 mm

Scintillator-strip R&D extruded reflector bad matching extruded reflector good matching extruded TiO 2 Kuraray reflector thickness:2mm Kuraray reflector Kuraray reflector reference Beam position (mm) Signal (ADC counts) extruded TiO 2 Good matching Test effects of covering material silver sheet or white paint(TiO 2 ) Photo-sensor matching With or without fiber Thickness To improve the strip performance, choosing right wrapping material position matching with fiber and MPPC WLS fiber for readout are necessary.

Further Improvement of the strip response uniformity Light through WLS fiber … uniform Light NOT through the fiber … not uniform Shading the “direct” light improves the non-uniformity. WLS fiber (1mm  ) Photon sensor surface (1x1 mm) MPPC WLS fiber Position along the strip Strip response Light through fiber Light NOT through fiber

Strip Response Non-uniformity MPPC Scintillator strip Position along the strip (cm) Strip response (ADC counts) MPPC Scintillator strip Before improvement After improvement (direct light shield & reflector) Kuraray fiber strip

1 st small prototype performance (tested in 2007 at DESY, 1-6 GeV e + ) Tungsten (3.5 mm thick) Scintillator layer (3 mm thick) The 1 st prototype tested at DESY electron synchrotron. Results show sufficient feasibility in 1-6 GeV e + energy.

The ScECAL 2 nd Test Module The final test module to establish the ScECAL feasibility. Sandwich structure with scintillator-strips (3 mm) and tungsten layers (3.5 mm). Extruded scintillator and new generation photon sensor (MPPC) are fully adopted. Strips are orthogonal in alternate layers. 72 strips x 30 layers = 2160 channels. Overall size ~ 20 x 20 x 25 cm.

Beam Test in Sep MTBF Objective : Establish the feasibility of Scintillator-ECAL + Analog HCAL with various types of beams in wide energy range. – Energy resolution, Linearity for electrons and pions. – Position and angular scan. –  0 reconstruction ability of the Scitillator-ECAL Beam running during Sep 3 rd – 29 th 2009 at FNAL Meson Test Beam Facility.

The Fermilab Meson Test Beamline Various types of beams available 1-32 GeV electrons 1-60 GeV pions 32 GeV muons 120 GeV protons Cerenkov counter available to discriminate electron or pion.

Very Preliminary Results 16 GeV e - (ScECAL only) 16 GeV  - ScECAL linearity for electron GeV Electron energy spectra ScECAL Analog HCAL Tail catcher

 0 runs (Very preliminary) Ability of  0 reconstruction from 2  is useful to improve jet energy resolution. Generate  0 by putting iron on beamline and injecting GeV  - beam. Try reconstruction of the generated  0 with Scintillator-ECAL.  0 ->2   0 detection is successful!

Summary Study of the Scintillator-strip ECAL is extensively underway in CALICE collaboration. Development of base components (strip + MPPC) is in good shape and almost done. Beam Test has been performed to establish feasibility of the ScECAL. – Observing event shape with the fine granular calorimeter. – Energy resolution, Linearity comparable with expectation. – First trial of  0 reconstruction with the ScECAL is successful. Next step : Further improvement of base component and simulation study.

Backups

MIP response map ADC counts Muon MIP signal (very preliminary)

Gain monitoring by LED and notched fiber Nice pedestal-1pe peak separation has been observed on ~70% of all channels. For other channels, electrical noise on readout board was too large to perform the gain measurement. Investigation is underway.