Research
Research at the J-PARC Hadron Experimental Facility focuses on the origin and evolution of matter. Why did a matter-dominated universe emerge, and are the elementary particles we know the only ones that exist? Through the KOTO and COMET experiments, we explore the origin of matter. Through physics experiments at the K1.8, K1.8BR, and high-p beamlines, we also investigate how matter, such as hadrons and atomic nuclei, formed from elementary particles and has evolved.
The following sections introduce experiments and research plans at the Hadron Experimental Facility, including K1.8, K1.8BR, K1.1, KL, High-p, COMET and facility-extension projects.
Identifiers, beamlines and categories follow the public PAC41 approval summary (April 3, 2026 version), checked on September 18, 2026.
J-PARC PAC / Proposal archive / Hadron Facility Extension
Approved experiments (preparation, running and analysis)
[E03] Measurement of X rays from Ξ- Atom
K1.8 — Stage 2[E08] Pion double-charge exchange on oxygen
K1.8 — Stage 1[E10] Neutron-rich Lambda hypernuclei
K1.8 — Stage 2[E14] Proposal for KL→π0νν Experiment at J-PARC
KL — Stage 2[E16] Nuclear-medium effects on vector-meson spectra
High-p — Stage 2 (first 300 hours)[E18] Weak decays of carbon-12 Lambda hypernuclei
K1.8 — Stage 2[E21] COMET: muon-to-electron conversion
COMET — Stage 2[E22] Lambda-nucleon weak interactions in A=4 hypernuclei
K1.8 — Stage 1[E26] Omega mesons bound in nuclei and mass modification
K1.8 — Stage 1[E29] Phi-meson nuclear bound states
K1.1 — Stage 1[E45] Baryon resonances through three-body reactions
K1.8 / K1.8BR — Stage 2[E50] Charmed-baryon spectroscopy
High-p — Stage 1[E57] Kaonic-deuterium X-ray spectroscopy
K1.8BR — Stage 1[E63] Hypernuclear gamma spectroscopy: second stage of E13
K1.1 / K1.8 — Stage 2[E70] Xi hypernuclei with S-2S: successor to E05
K1.8 — Stage 2[E72] Narrow Lambda resonance search with hypTPC
K1.8BR — Stage 2[E75] Double-Lambda hypernuclei through decay-pion spectroscopy
K1.8 — Stage 2[E79] Isospin-3 dibaryon search
High-p — Stage 1[E80] Light kaonic nuclei
K1.8BR — Stage 2[E86] Polarized Lambda-proton scattering
K1.1 — Stage 1[E88] Phi mesons in nuclei through charged-kaon pairs
High-p — Stage 1[E89] Properties of the antikaon-two-nucleon system
K1.8BR — Stage 1[E90] Precision study of the Sigma-N cusp
K1.8 — Stage 2[E94] Lambda-hypernuclear spectroscopy with S-2S
K1.8 — Stage 2[E95] Phi production with a pion beam
High-p — Stage 1[E97] Excited Xi baryons
High-p — Stage 1[E104] Near-threshold phi-pair production in antiproton-proton reactions
K1.8BR — Stage 2[E107] KOTO II
KL2 (extension) — Stage 1
Proposals awaiting further review
These proposals are listed separately from approved experiments.
[P84] High-resolution Lambda spectroscopy at HIHR
HIHR (extension) — Deferred[P85] Omega-baryon spectroscopy at K10
K10 / T2 (extension) — Deferred[P87] Dielectrons from heavy-ion collisions with upgraded E16
High-p / heavy ions — Deferred[P91] Nucleon charm content through J/psi measurements
High-p — Deferred[P92] E80 Phase I: antikaon-three-nucleon states via Lambda-d decay
K1.8BR — Deferred[P93] Secondary-beam performance studies
High-p — Deferred[P102] The 1680-MeV structure in pion-induced eta production
K1.8 — Deferred[P111] Near-threshold J/psi production with pions
High-p — Deferred[P115] Antideuteron-carbon interactions
K1.8 — Deferred
Experiments with completed beam runs (including analysis)
[E05] Spectroscopic Study of Ξ-Hypernucleus, 12ΞBe, via the 12C(K-,K+) Reaction
K1.8 — Finished[E07] Systematic Study of Double Strangeness System with an Emulsion-counter Hybrid Method
K1.8 — Finished[E13] Gamma-ray spectroscopy of light hypernuclei
K1.8 — Finished[E15] A Search for deeply-bound kaonic nuclear states by in-flight 3He(K-,n) reaction
K1.8BR — Finished[E19] High-resolution Search for Pentaquark in π-p→K-X Reactions
K1.8 — Finished[E27] Antikaon-proton-proton bound-state search
K1.8 — Finished[E31] Subthreshold hyperon resonances in deuterium reactions
K1.8BR — Finished[E36] Kaon leptonic-decay ratios and sterile-neutrino searches
K1.1BR — Finished[E40] Sigma-proton scattering
K1.8 — Finished[E42] H-dibaryon search with hypTPC
K1.8 — Finished[E62] Kaonic-atom spectroscopy using TES
K1.8BR — Finished[E73] Lifetimes of light hydrogen hypernuclei
K1.8BR — Finished[E96] Xi-carbon X-rays with an active target
K1.8 — Finished
Beam and detector test experiments
[P109] Low-momentum kaon beam optimization
K1.8BR — Test Experiment[T112] Secondary-beam characterization: second stage of P93
High-p — Test Experiment[T113] Multi-GeV muon radiography
High-p — Test Experiment
Selected recently completed test experiments
[T98] Antimatter reactions in a liquid-argon TPC
K1.8BR — Finished[T103] Streaming data-acquisition tests
K1.8BR — Finished[T105] Test-beam-line development
K1.8BR — Finished[T106] Secondary-beam tests: first stage of P93
High-p — Finished[T108] Antideuteron beam optimization
K1.8 — Finished[T110] Trigger-counter tests for E72
K1.8BR — Finished
Earlier entries and related experiments
PAC39 approval summary: these earlier entries are not separate entries in the PAC41 summary.
[E06] Measurement of T-violation Transverse Muon Polarization in K+→π0μ+ν Decays
K1.1BR — PAC39: E36 as the first step[E17] Precision spectroscopy of Kaonic 3He 3d→2p X-rays
K1.8BR — PAC39: registered as E62 with an updated proposal