Fine granular calorimeter with scintillator strips and new photon sensor readout

The Global Large Detector (GLD) is one of the detector concepts proposed for the future linear collider experiment. At the linear collider experiment Particle Flow Algorithm plays an important role in achieving excellent jet energy resolution (∼30%/√E). This method requires a finely segmented calorimeter able to separate individual particles inside jets in the calorimeter. The GLD calorimeter is a sampling calorimeter which consists of scintillator and absorber (tungsten for electro-magnetic, lead or iron for hadron calorimeter) layers. It has a scintillator-strip structure; strips in successive scintillator layers are aligned in orthogonal directions to achieve effective 1 × cm² segmentation. To read out the signal from all the individual scintillator strips, we adopt a new photon sensor, the Multi-Pixel Photon Counter (MPPC). The MPPC consists of 100-1600 APD pixels, each of which works in the limited Geiger mode. This new photon sensor has many excellent features (compact size, low cost, high gain and photon detection efficiency and insensitivity to magnetic fields) and is suitable for use in the GLD calorimeter readout. We have tested 800 samples of 1600-pixel MPPCs and confirmed that the performance is satisfactory for calorimetric use. We have also constructed an electromagnetic calorimeter test module with 468 scintillator strips and full MPPC readout, and performed a beam test using a 1-6 GeV positron beam to evaluate its performance. The test module was measured to have good performance (energy resolution is (13.45 ±0.07)%/√E ⊕ (2.87 ±0.08)%, deviation from linearity is less than 4%), showing that the 1600-pixel MPPC is suitable for the readout of finely segmanted calorimeters.