What are Hadrons?

Hadrons are composite particles -one type of subatomic particles- made up of quarks, and held together by the "strong force" -one of the four fundamental interactions of nature- carried by gluons. Hadrons are categorized into two groups: baryons and mesons. Three quarks combine to produce one baryon. Well-known baryons include the proton and the neutron that combine to form atomic nuclei. Mesons, on the other hand, are comprised of one quark and one anti-quark. The most familiar mesons are the pion and the kaon. For the prediction of the pion Dr. Hideki Yukawa was awareded the Nobel Prize in Physics in 1949, two years after its discovery.

The current theory estimates that our universe was created in the so-called "Big Bang" some 13.7 million years ago. It is believed that in its infancy, the temperature of the universe was extreme and it resembled a boiling soup of elemental particles (the other type of subatomic particles), such as quarks, gluons, and electrons. As the universe expanded and cooled, the quarks and gluons condensed into hadrons (e.g., protons and neutrons). The combination of hadrons led to the formation of atominc nuclei, and then with the addition of electrons, atoms -fundamental blocks of matter- were realised. Thus, the study of atomic nuclei and elementary particles is a journey in time back through the history of the universe.



Overview of the Hadron Experimental Facility
(Hadron Hall)

The Hadron Hall is a research facility designed to investigate the fundamental components of matter and to measure their interactions with extremely high precision. In modern physics, a high-intensity proton beam is essential for the production and study of exotic nuclear states and elementary particles, and in the search for rare physical phenomena.

Within the Hadron Hall, the primary high-intensity proton beam is used to produce a variety of secondary particles such as kaons, pions, hyperons, neutrinos, muons, and anti-protons. To achieve this, the proton beam is extracted from the 50 GeV synchrotron and directed to a target station. The collision between the the proton beam and the target generates the secondary particles which are directed towards an experimental area where a range of experiments can be carried out simultaneously (See the illustration below).
Construction of the Hadron Hall began in 2004 and was completed in January 2009 with the first proton beam being successfully extracted in January of that year. Secondary-particle beams have been available for user experiments at the Hadron Hall since January 2010. In March 2020, high-momemtum beam line which can deliver a part of the primay proton beam was completed and the experiment using primary proton beam has been started. A new primary beam line for search for leption flavor violating muon-electron convesion is under construction.

Please click here for the announcement of the results so far.


Major Research Topics

In Hadron Experimental Facility, high-intensity secondary beams such as kaons and pions thanks to high-intensity primary proton beam from 50 GeV synchrotron.  At present 3 secondary beamlines (K1.8, K1.8BR, and KL) and 1 primary beamline (high-momentum) are in operation for the following reseaches on experimental particle and nuclear physics. Experiment to search for lepton flavor violating muon-electron conversion (COMET Experiment) is under preparation.