Fujioka Lab. @ Tokyo Tech

We utilize subatomic nuclei as a tool to investigate hadron properties, hadron-hadron interaction, parity/time-reversal violation in compound nuclei. Furthermore, we search for non-usual nuclear systems such as double- hypernuclei and tetra-neutrons.

Research Topics


A hypernucleus contains at least one hyperon, which is a kind of baryon with strange quarks, in a nucleus. As the lightest hyperon is a hyperon, only 1.2 times heavier than a proton and neutron, -hypernuclei are the most studied both experimentally and theoretically. We will search for a double- hypernucleus, which has two hyperons, at J-PARC.
[reference] J-PARC E75 proposal ”Decay Pion Spectroscopy of  produced by -hypernuclear Decay”

Mesonic atoms and Mesonic nuclei

Mesons comprising a quark () and an antiquark () can be also a constituent in a meson-nucelus system, named a mesonic nucelus. If a meson has a negative electric charge, it can orbit around an atomic nucleus, like an electron but with a much smaller orbit radius. Spectroscopy of mesonic atoms and mesonic nuclei will provide information on strong interaction between the meson and the nucleus, and chiral symmetry breaking and its partial restoration at finite density, which significantly affect the properties of mesons.

Time-reversal violation in compound nuclei

The nucleon-nucleon force in weak interaction sector violates parity symmetry, even if it is very difficult to observe because of strong interaction. It is experimentally confirmed that the parity symmetry breaking can be enhanced in a compound nucleus. Similarly, time-reversal violation is also enhanced in a compound nucleus. We plan to carry out a scattering experiment with a polarized epi-thermal neutron beam and a polarized nuclear target such as .


We search for a hypothetical charge-neutral nucleus, comprising only neutrons. In particular, a four-neutron system named tetraneutron attracts interest. Different from various experiment using nuclear reactions to populate tetraneutrons, we seek for a signature of tetraneutron as a product of thermal-neutron induced ${}^{235}\mathrm{U}$ fission.

Members in FY2023

Associate ProfessorHiroyuki FUJIOKAfujioka[at]phys.titech.ac.jp
Assistant Professor Makoto UCHIDAuchida[at]phys.titech.ac.jp
graduate student (master’s course)Chiaki UNEune[at]quark.ap.titech.ac.jp
graduate student (master’s course)Takumi KOBORIkobo[at]quark.ap.titech.ac.jp
graduate student (master’s course)Gakutaro NISHIMURAnishi.g[at]quark.ap.titech.ac.jp
graduate student (master’s course)Tomoki KOBAYASHIkobayashi[at]quark.ap.titech.ac.jp
graduate student (master’s course)Naoki HAGIWARAhagiwara[at]quark.ap.titech.ac.jp
undergraduate studentShunya Oikawaoikawa[at]quark.ap.titech.ac.jp
undergraduate studentChiaki KASUMIchiaki.k[at]quark.ap.titech.ac.jp
undergraduate studentShuma NAKAHARAnakahara[at]quark.ap.titech.ac.jp

Contact Address

fujioka[at]phys.titech.ac.jp (Hiroyuki Fujioka)