Extreme Forward Calorimeter, EFC

In order to improve the experimental sensitivity to some physics processes such as $B\rightarrow \tau\nu$, the extreme forward calorimeter, EFC, is needed to further extend the polar angle coverage by ECL, 17$^o$ $< \theta <$ 150$^o$ [4]. EFC covers the angular range from 6.4$^o$ to 11.5$^o$ in the forward direction and 163.3$^o$ to 171.2$^o$ in the backward direction. The EFC detector is attached to the front faces of the cryostats of the compensation solenoid magnets of the KEKB accelerator, surrounding the beam pipe [6,7]. EFC is also required to function as a beam mask to reduce backgrounds for CDC. In addition, EFC is used for a beam monitor for the KEKB control and a luminosity monitor for the Belle experiment. It can also be used as a tagging device for two-photon physics.