28.11.2011

DESY engages in Belle II

Cooperation agreement with KEK at new Super B-factory

On 18 November, the laying of the foundation stone for the SuperKEKB accelerator took place at the Japanese accelerator laboratory KEK in Tsukuba. This accelerator with the corresponding particle detector Belle II will become a so-called Super-B-factory. Seven German universities, the Max Planck Institute in Munich and DESY will jointly build the pixel vertex detector for this ambitious experiment. The DEPFET technology, originally designed for the ILC, will be used for this purpose for the first time. On occasion of the foundation stone laying ceremony, there was an agreement with KEK on the participation of the German research institutes in the construction of Belle II, including future data taking and data evaluation.

SuperKEKB is to produce the 40-fold data rate of its predecessor KEKB.

The Belle II experiment at the Super KEKB accelerator is to solve one of the major particle physics mysteries: why is there only matter in today’s universe when – according to current theories – matter and antimatter emerged in equal proportions at the Big Bang? Physicists attribute this imbalance to the violation of the so-called CP symmetry which explains why matter and antimatter behave differently. Scientists have already identified processes which violate this CP symmetry. However, the amount of observed CP violations is far from sufficient to explain in quantitative terms the actually existing surplus of matter. With the purpose to investigate these processes more thoroughly, Super KEKB will bring electrons and protons to collision, to generate large quantities of B-mesons. The decay of these occurring in the Belle II detector will be measured with highest precision.

“The Belle II engagement is a logical continuation of our detector development work for the ILC. Our participation at the construction of the pixel detector perfectly matches the corresponding DESY activities at the LHC experiments,” research director Joachim Mnich declares. “With the current cooperation agreement, we continue the tradition of 40 years of a very fruitful cooperation with Japanese particle physics institutes.” Accordingly, also the Japanese scientists’ community was extraordinarily pleased with DESY’s participation at Belle II.

SuperKEKB is an extension of the KEKB accelerator ring, running from 1999 to 2010. The remodeling of the approximately 3-kilometres facility costing 400 million euros will increase the collision rate by a factor of 40, thus producing more than 3000 pairs of B-mesons per second. Currently, about 420 scientists from 58 institutes of 14 nations belong to the Belle II collaboration; with Germany representing the second largest group of physicists, after Japan. End of 2014, Super KEKB will accelerate the first particles; in 2015, the Belle II detector will take up regular operation. The planned experiments with record collision rates at Super KEKB will complement those at the LHC, which are also investigating B-mesons with its LHCb detector.

Collaboration with Japanese scientists started at the DORIS experiment DASP and continued at PETRA with the JADE („JApan-Deutschland-England“) experiment. At HERA, there was a major Japanese participation at the ZEUS and HERMES experiments. Also within the framework of future projects, as for example detector development for the International Linear Collider ILC, there are joint research activities which, with the new cooperation of DESY and KEK, were for the first time extended to an experiment in Japan.

Signing of the MoU for the German participation in Belle II with Carsten Niebuhr and Manfred Fleischer from DESY (from left). Photo: B. Wankerl, Universe Cluster