Experimental Nuclear and Particle Physics
Experimental Particle Physics (Accelerator)
|Professor :||Hitoshi Yamamoto|
|Associate Professor :||Tomoyuki Sanuki|
|Assistant Professor :||Tadashi Nagamine||Akimasa Ishikawa||Ryo Yonamine|
Collision of electron and positron at high energy can produce various heavy particles such as B mesons and, in the future, possible Higgs bosons and new particles that may signal entirely new theory of physics.
The BELLE experiment operates at the electron-positron collider (called ’B-factory’) at the high energy phyisics laboratory in Tsukuba (KEK). There, electron and positron collide to produce particles that contain beauty quark, charm quark, and tau leptons. In decays of B mesons, that contain a beauty quark, phenomena that violate matter-antimatter symmetry have been discovered. Such asymmetry is called CP violation that may play an important role in explaining why antimatter has disappeared in the universe. The effect was exactly as predicted by the theory proposed by Kobayashi and Maskawa leading to their receiving a Nobel prize. The facility is now being upgraded to increase the luminosity by factor of 40 – it is called the Super KEKB project. The Tohoku group designed and built the region of the detector very close to the collision point, playing an important role in the silicon tracker, and is extensively involved in the physics analysis.
The future of electron-positron collider is in linear colliders. The International Linear Collider (ILC) collides electron and positron at en energy several hundred times greater than that of the B-factory. Its shape is linear, its length is about 30 km initially which is to be upgraded to about 50 km in the future. Kitakami mountains is a strong candidate as the ILC site. The main goal of the machine is to produce the Higgs particles and study it in detail, and to search new physics beyond the standard model such as the particle responsible for the dark matter. At the and of 2012, a Higgs-like particle was discovered at the LHC accelerator installed at the CERN laboratory located near Geneva. This indeed mark a beginning of a new era for the particle physics. The LHC will be upgraded in the near future, but the ILC will have on average several tens of times more statistical power than the LHC even after its upgrade, even though the detail will depend on physics modes being studied. A new international organization for the linear collider (Linear Collider Collaboration – LCC) has been inaugurated in February 2013, and this group assumed the position of the associate director of physics and detectors. We also serves as the headquarter of the Japanese ILC detector R&Ds. In concrete terms, we develop detailed computer programs to evaluate how accurately an ILC detector can measure physical quantities, and use them to design and optimize the detector. ILC detectors need unprecedented resolutions in position measurement of particle tracks, their momenta, and energy of quark jets and that requires R&Ds for detector technologies. We are engaged in R&Ds for a vertex detector using state–of-the-art semiconductor technology.