The DEPFET active pixels for Belle II—resolution in thinned sensor

The DEPFET technology of active pixel sensors has been chosen for the new Belle II experiment at the SuperKEKB collider in Japan. The in-pixel amplification of the DEPFET technology allows to use very thin low noise sensors. The front-end electronics and the data acquisition concepts supporting the integration into Belle II are finalized and the two-layer detector (PXD) will be ready to provide data of its 7.6 million pixels in 2015. erating principle of the PXD with its expected performance in Belle II is presented, focusing on the resolution properties of the planned 75 μ m thick sensor. First successful tests in pion beams at CERN with prototype DEPFET pixel matrices thinned down to 50 μ m provide results that conform with expectations. These results are presented, together with analysis of the residual distributions as functions of the incident angle. The measurements are compared with Monte Carlo simulations.