Upgrade of the Belle Silicon Vertex Detector

The Belle experiment at KEK (Tsukuba, Japan) was inaugurated in 1999 and has delivered excellent physics results since then, which were, for example, recognized in the Nobel Prize award 2008 to Kobayashi and Masukawa. An overall luminosity of 895 fb−1 has been recorded as of December 2008, and the present system will be running until 1 ab−1 is achieved. After that, a major upgrade is foreseen for both the KEK-B machine and the Belle detector. y in 2004, the Letter of Intent for KEK Super B Factory was published. Intermediate steps of upgrade were considered for the Silicon Vertex Detector (SVD), which performs very well but already got close to its limit regarding the occupancy in the innermost layer and dead time. Eventually it was decided to keep the existing SVD2 system until 1 ab−1 and completely replace the silicon detector as well as its readout system for Super-Belle. ture SVD will be composed of double-sided silicon sensors as the present detector, but equipped with faster readout electronics, namely the APV25 chips originally made for CMS at CERN. Moreover, it will be enlarged by two additional layers and equipped with a double layer of DEPFET pixel detectors surrounding the beam pipe. The silicon sensors will be fabricated from 6 in. wafers (compared to the current 4 in. types) and the readout chain will be completely replaced, including front-end, repeaters and the back-end electronics in the counting house.