K. Adamczyk

Construction and test of the first Belle II SVD ladder implementing the origami chip-on-sensor design

The Belle II Silicon Vertex Detector comprises four layers of double-sided silicon strip detectors (DSSDs), consisting of ladders with two to five sensors each. All sensors are individually read out by APV25 chips with the Origami chip-on-sensor concept for the central DSSDs of the ladders. The chips sit on flexible circuits that are glued on the top of the sensors. This concept allows a low material budget and an efficient cooling of the chips by a single pipe per ladder. We present the construction of the first SVD ladders and results from precision measurements and electrical tests.

Belle II silicon vertex detector

The Belle II experiment at the SuperKEKB collider in Japan is designed to indirectly probe new physics using approximately 50 times the data recorded by its predecessor. An accurate determination of the decay-point position of subatomic particles such as beauty and charm hadrons as well as a precise measurement of low-momentum charged particles will play a key role in this pursuit. These will be accomplished by an inner tracking device comprising two layers of pixelated silicon detector and four layers of silicon vertex detector based on double-sided microstrip sensors. We describe herein the design, prototyping and construction efforts of the Belle-II silicon vertex detector.

Search for CP violation in tau -> K^0_S pi nu_tau decays at Belle

We report on a search for CP violation in tau(+/-) -> K-S(0)pi(+/-)nu(tau) decays using a data sample of 699 fb(-1) collected by the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K-S(0)pi(+/-) system and found to be compatible with zero with a precision of O(10(-3)) in each mass bin. Limits for the CP violation parameter Im(eta(S)) are given at the 90% confidence level. These limits are |Im(eta(S))| < 0.026 or better, depending on the parametrization used to describe the hadronic form factors, and improve upon previous limits by 1 order of magnitude.