Quarks, the smallest constituents of matter, cannot exist on their own and form composite particle states called 'hadrons,' such as protons, neutrons, and mesons. Typically, these hadrons are composed of three or two quarks, but recent research has yielded experimental results suggesting the existence of particles with five quarks and hadron molecule-like states. These particles are referred to as 'exotic' particles.。

Through the study of these exotic particles and hadron excited states, we aim to uncover the internal structure and properties of hadrons. Additionally, we are exploring phenomena where hadrons are produced within the conditions similar to the early moments of the universe, which have densities comparable to those found in atomic nuclei. We are investigating instances where the mass of these hadrons becomes lighter, seeking to understand the fundamental question of the origin of mass. We are advancing experiments that involve the irradiation of high-energy photon beams onto targets such as protons and atomic nuclei to 'photoproduce' these hadrons."