J. Suzuki

Beam test of radiation hardness of a scintillating tile/fiber calorimeter

Abstract Radiation hardness of a scintillating tile/fiber calorimeter is studied by irradiating electromagnetic test modules with 2.5 GeV electrons at the KEK linac. The induced damage is evaluated in a 2 GeV electron test beam by measuring the reduction in pulse height after irradiation. The pulse height peak for 2 GeV electrons is found to decrease by 19.3 ± 1.3% for a dose of 0.61 Mrad and 14.9 ± 2.7% for 0.33 Mrad. In addition to these modules, several tile/fiber assemblies were irradiated up to 4.8 Mrad and the damage as a function of dose was measured with a radioactive source. Effects of radiation damage on the linearity and energy resolution at higher energies are evaluated using a GEANT simulation and the measured damage.

Optics of large scintillating tiles with wavelength shifting fiber readout — application to a hadron calorimeter

Abstract Light yield and response uniformity of a scintillating tile/fiber system were measured for tiles with a side length up to ∼50 cm. With increasing the tile size, the light yield at the tile center decreases and the nonuniformity measured near the tile edges increases gradually. These tile size dependences originate in the light attenuation in the scintillator, and hence are specific to the scintillator type. Radiation hardness of large tile/fiber systems was compared with that of small tile/fiber systems. The SDC barrel hadron calorimeter was used as a model to evaluate the performance of a calorimeter composed of tile/fiber systems with such a lateral nonuniformity and with light yield variation in depth. In the evaluation the hadronic shower profile was given by a GEANT simulation and the Hanging File testbeam data.

Level-1 silicon vertex detector trigger at Belle

We present a newly developed fast trigger system that uses the silicon vertex detector (SVD) for the Belle experiment at the KEKB energy-asymmetric e/sup +/e/sup -/ collider. It is designed to issue the trigger with a latency of 1.85 /spl mu/s for the Belle central trigger system (GDL). The primary purpose of the SVD trigger is to reduce beam-induced background events by requiring tracks that come from the interaction point. The system receives trigger signals from VA1TA front-end integrated circuits, which read out signals on the silicon-strips. SVD tracks are constructed with them in combination with the trigger information of the central drift chamber (CDC), which is located outside the SVD. Performance of the SVD trigger is evaluated with collision data.

The Belle L1.5 trigger

During the summer shutdown of 2003 the new silicon vertex detector SVD2 was installed in Belle at the KEK-B factory in Tsukuba, Japan and started to take data in October 2003. It provides important improvements in the tracking capabilities and adds new trigger functionality. In addition a new hardware trigger level 1.5 was designed and installed that takes advantage of the digitized SVD hit data. The improvement in the Belle trigger system is important to deal with the increasing luminosity and higher beam currents of the KEK-B collider. The design of the level 1.5 trigger system is reviewed and results from the data taking are presented.