Silicon Vertex detector for Belle II

The Belle II experiment at the SuperKEKB collider in Japan is designed to
probe new physics at the luminosity frontier using approximately 50 times
the data recorded by its predecessor (Belle). A precise determination of
the position of decay points of subatomic particles and the measurement of
low-momentum charged particles will play a key role in this pursuit. These
will be accomplished by a six-layer vertex detector, comprising two layers
of pixelated silicon detector followed by four layers of silicon vertex
detector (SVD). Each detector module (“ladder”) of the SVD Layer# 3, 4, 5
and 6 is composed of two, three, four and five double-sided silicon
microstrip sensors, respectively. These sensors are individually read out
by APV25 chips. The central sensors for Layer# 4 to 6 rely on an
innovative “Origami” chip-on-sensor concept, in which the readout chips
sit on flexible hybrid circuits, glued on the top of the sensors. The
concept allows for a low material budget (of paramount importance for the
above designed goals) and minimizes the input capacitance of the readout
system, effectively reducing the noise.

Our group has been leading the design, prototyping and construction of the
SVD Layer# 4. The colloquium provides a glimpse of this exciting detector-
building effort at TIFR and in Japan.