Description
The Japanese High Energy physics community, JAHEP (Japan Association of High Energy Physicists) provides Japan's Updated Strategy for High Energy Physics for the ESPP Update 2026. High energy physics research in Japan encompasses a variety of groundbreaking experiments conducted at major facilities. These include the SuperKEKB accelerator and the Belle II experiment, which focus on search for new physics in heavy flavor decays; the high power proton accelerator complex J-PARC, where experiments are conducted using the high intensity neutrino, kaon, muon and neutrons beams; and collaborative efforts in CERN's Large Hadron Collider (LHC and HL-LHC) experiments. For neutrino research, the construction of the Hyper-Kamiokande experiment started and is currently underway. We emphasize the importance of maintaining timely progress in these ongoing experiments and construction of experimental facilities. We acknowledge significant contributions by European collaborators to the Japan-based experiments, and wish to see more participation. We also acknowledge essential support of CERN to the experiments as a key hub for the European activities.
Looking into the future, the early realization of a Higgs factory through international collaboration is crucial for our field. We take into account the evolving situation of Higgs factory proposals: CEPC, FCC-ee, ILC, and LC@CERN. To ensure the realization of a Higgs factory, we pursue the following key directions:
- We prioritize efforts to realize the ILC as Global Project, taking a leading role in advancing ongoing initiatives. We will engage with international partners to discuss governance, responsibilities, and site selection. We intend to develop and expand our scientific and promotional activities to host the ILC as Global Project in Japan.
- We also extend our activities in other Higgs factory proposals as a collective approach to maximize the chances of timely realizing a Higgs factory.
In addition, the ILC Technology Network (ITN), international R\&D framework for the ILC accelerator initiated by KEK and ILC International Development Team (IDT), has started. The collaboration with CERN is essential for ITN. The detector R&D with test beams are essential for future experiments, and we would promote international collaborations in detector developments, such as ECFA-Detector R&D. Beyond a Higgs Factory, developing high-field magnets using state-of-the-art superconductors is critical to realize a future hadron collider.
By advancing current and future projects, we aim to continue contributing to fundamental discoveries and to foster international collaboration. We will actively participate in international discussions on shaping the global strategy for high-energy physics.
