High Energy Physics Lab.
In the High Energy Physics laboratory, we are conducting experimental researches of particle physics mainly using high energy particle accelerators. Currently, the following projects are on our active phase:
- T2K (Long baseline neutrino oscillation experiment)
- Hyper-Kamiokamde (Particle physics experiment using the ultra large-scale water Cherenkov detector)
- DeeMe (Search for charged lepton flavor violation)
- CDF (High energy proton-antiproton collision experiment)
Through these experiments, we are making an investigation of a fundamental nature of elementary particles which are the smallest unit of matter as well as the origin of force, and also searching for a new physics beyond the standard model.
As indicated by the name “High Energy Physics”, we need high energy in order to research particle physics because of the following two main reasons.
The first reason is that shorter wave length is necessary to look at smaller things. When we can see the structure of cells and crystals with high resolution by using an electron microscope, we are taking advantage of short-length matter wave of an accelerated electron. In the same manner, it becomes possible to see an even smaller structure of nuclei and protons by using particles with even shorter wave length, that is, particles having higher kinetic energy as a probe. The correspondence relationship between “a microscopic world” and “high energy” comes out from this aspect.
The second reason is that high energy is needed to produce a heavy particle. Einstein’s theory of relativity gives an relationship of E = mc2 between energy E and mass m, and in another word, a heavy-mass particle can be produced by concentrating high energy. In practice, a collision between particles with quite high energy brings about the phenomenon that new particles which are not constituents of the colliding particles are produced. Many new particles predicted by theory have been discovered in this way. The Higgs boson discovered in 2012 is one of them, although there are still many particles yet to be discovered. Also, in order to investigate property of particles which are known but does not exist around us, we need to produce them first. As described above, “high energy” will be used as a means to produce particles.
Moreover, by the observation finding that the current universe is expanding, it turned out that the universe was born from an extremely small and energetic situation by Big Bang. This provided the close relationship between particle physics and cosmology. It can be said that the behavior of elementary particles at the early universe determined the shape of the present universe. For example, there are little or no anti-matter in the present universe, while particles are always produced in a reaction by pair-production of a particle and an anti-particle. It is also becoming evident that a galaxy cannot be formed by only ordinary matter. A key to solve these problems is expected to lie in particle physics.