Meson RIKEN ECL Research Team

Research Areas

We are conducting experiments aimed at generating a novel form of nuclei or matter where a meson is bound as a real particle, although mesons are typically considered virtual particles within a nucleus. Specifically, our focus lies in embedding a kaon, which contains a strange quark, into nuclei. It is suggested that the density of kaonic nuclei increases, potentially revealing new properties and quark degrees of freedom within the nucleus.

Furthermore, we are engaged in interdisciplinary research, such as muon atomic experiments, utilizing state-of-the-art superconducting X-ray detectors known as TES detectors.

Research Subject

1. Search for nuclear-bound states containing a meson and study their properties.
2. Study of basic property of few-body hypernuclei.
3. Application of superconducting X-ray detectors
4. Atomic, molecular, nuclear, and fundamental physics studies by precision X-ray measurements of muonic atoms

List of Selected Publications

1. T. Akaishi, et al. (J-PARC E73/T77 collaboration):
   “Precise lifetime measurement of 4ΛH hypernucleus using in-flight 4He(K-, π0)4ΛH reaction”
   Phys. Lett. B 845, 138128 (2023).
2. T. Okumura et al.:
   “A Proof-of-Principle Experiment for Testing Strong-Field Quantum Electrodynamics with Exotic Atoms: High Precision X-ray Spectroscopy of Muonic Neon”
   Phys. Rev. Lett. 130, 173001 (2023).
3. S. Aikawa et al. (J-PARC E31 collaboration):
   “Pole Position of Λ(1405) Measured in d(K-, n)πΣ Reactions”
   Phys. Lett. B 837, 137637 (2022).
4. T. Hashimoto et al. (J-PARC E62 collaboration):
   “Measurements of Strong-Interaction Effects in Kaonic-Helium Isotopes at Sub-eV Precision with X-Ray Microcalorimeters”
   Phys. Rev. Lett. 128, 112503 (2022).
5. T. Okumura, et al.:
   “Deexcitation Dynamics of Muonic Atoms Revealed by High-Precision Spectroscopy of Electronic K X rays”
   Phys. Rev. Lett. 127, 053001 (2021).
6. T. Yamaga, et al. (J-PARC E15 collaboration):
   “Observation of a KbarNN bound state in the 3He(K-, n) reaction”
   Phys. Rev. C 102, 044002 (2020).
7. S. Okada et al.:
   “First application of superconducting transition-edge-sensor microcalorimeters to hadronic-atom x-ray spectroscopy”
   Prog. Theor. Exp. Phys. 2016, 091D01 (2016).
8. S. Ajimura et al. (J-PARC E15 collaboration):
   ""K-pp", a Kbar-meson nuclear bound state, observed in 3He(K-,Λp)n reactions"
   Physics Letters B 789, 620 (2019).
9. Y. Sada et al. (J-PARC E15 collaboration):
   "Structure near the K-+p+p threshold in the in-flight 3He(K-,Λp)n reaction"
   Prog. Theor. Exp. Phys. 2016, 051D01 (2016).
10. T. Hashimoto et al. (J-PARC E15 collaboration):
    "Search for the deeply bound K-pp state from the semi-inclusive forward-neutron spectrum in the in-flight K- reaction on helium-3"
    Prog. Theor. Exp. Phys. 2015, 061D01 (2015).