Sept. 28, 2023
@ Tsukuba U.

Particle and Nuclear Physics
at J-PARC
Takashi Kobayashi
J-PARC, JAEA/KEK

1

Versatile Quantum Beams for Microscopic World

Japan Proton Accelerator Research Complex
Power-frontier accelerators andmulti-purpose user facilities
Jointly operated by twoorganizations:
KEK, andJAEA

spallation

Variety of secondary particles generated withhigh-energy and high-intensity protons

2Japan Proton Accelerator
Research Complex：J-PARC

400MeV LINAC

J-PARC Facility(KEK/JAEA）
South to North

3 GeV RCS

Neutrino Beams(to Kamioka)
Materials and Life
Experimental Facility

Design intensity
RCS for MLF: 1MW
MR for PN : 750kW

CY2007 Beams
JFY2008 Beams
JFY2009 Beams

Hadron Exp.
Facility
Bird’s eye photo in January of 20083

Beam Power History at MLF
1 MW eq. pulse

1 MW eq. beam

830 kW

700 kW

Accident at
Hadron Facility

500 kW

Earthquake～10 months interruption
due to the earthquake～1 month interruption
due to the fire in MLF

Interruption due totroubles of Hg-target

as of Feb 8, 2023
4

Main ring upgrade plan
More Rapid Cycle:

2.48 s  1.32 s  1.16 s• Main Power Supply to berenewed• High gradient RF Cavity• Improve Collimator• Rapid cycle pulse magnet
for injection/extractionMore Protons /Pulse：• Improve RF Power• More RF Systems• Stabilize the beam withfeedback5MR beam power history• Before upgrade• FX:535kW、SX64kW achieved• After upgrade• FX:750kWeq@1.38s (single shot) acceleration succeeded• SX: 50kW/5.2s cycle w/ 99.5% ext. eff

6

J-PARC MR: High power study 令和5年4月16日 21時51分
J-PARC MRが、試験運転（1-shot運転）において、所期性能である750 kW相当の陽子ビームの30 GeV加速に成功 今夏にRF空洞一台を増設、その後、ビーム試験を重ねてビームロスの低減を図りながら利用運転時の陽子ビーム強度を徐々に増加 ➡ 750 kWの定常運転を目指す

750kWeq pulse acceleration succeeded7

SX30GeV study in June

• SX/HD 30 GeV tunings and operation in 5.2 s cycle
were performed for a week
• Achieved 50 kW in 5.2 s cycle after the upgradeswith extraction efficiency 99.5%.

8

Science at MLF w/ n/mu
Materials and life sciences

Hadron experiments
Explore origin of matter formation

Neutrino experiment
Explore origin of matter in the universe

Development Accelerator Driven nuclear
transmutation System: ADS

9Materials & Life Science Experimental Facility Neutron & Muon Beam Facility for Materials & Life Science
Liniac

70 m
32 m

140 m

The World Highest-Class
Neutron & Muon Sources.
Neutron Source:
 1MW
 Liq. Mercury Target Liq. H2 Moderators
Muon Target Station
2nd Experimental HallProton
Beam

Neutron Target Station
1st Experimental Hall

23 Beam Ports for Neutron Instruments
4 Beam Ports for Muon Instruments

Materials and Life Science Facility （MLF）
J-PARC

18

World Highest Intensityof Neutron Pulse Beam!

15JAEA’s technologies
Liq Ag target

US-SNSJ-PARC
Unit： 1012 n/(sr・pulse)5.9

ISIS – TS2

SNS48kW48 kW

2000 kW(2024goal)

4.0
1,000 kW(2009年12月)
1,400 kW
(2021.6)

1,000 kW (Design)

830 kW(2022.4)300
kWkW400(2012年11月)(2015年3月)

Coupled moderator

8.4

ISIS

11

23 beam ports
21 in operation

Neutron Instruments in MLF
Special Environment
Neutron Powder
Diffractometer
Super High
Resolution Powder
Diffractometer

High Pressure
Neutron
Diffractometer

Accurate NeutronVillage of neutron
Nucleus Reaction
resonance spin echo
Neutron Optics Measurement
spectrometers
andInstrument
Fundamental
Physics

Neutron Beam-linefor Observation andResearch UseIBARAKI
Biological Crystal
Diffractometer

BiomolecularDynamics
Spectrometer
4D Space Access
Neutron Spectrometer

High Resolution
Chopper
Spectrometer
proton beammuon target

Polarized Neutron
Spectrometer

neutron source

Cold Neutron
Disk-Chopper
Spectrometer
Energy Resolved
Neutron Imaging System
High Intensity Total
Diffractometer

Small and WideAngle Neutron
Scattering
Instrument
Soft Interface
Analyzer

Extreme Environment Single
Polarized Neutron Reflectometer Crystal Neutron Diffractometer

IBARAKI
Materials Design
Diffractometer
Engineering Materials
Diffractometer12

Neutron Instruments at MLF
Experimental
Hall No. 2

AMATERASBL14TAIKAN
BL15SOFIA

SHARAKU
iMATERIA

BL16

BL17

BL20Experimental Hall No. 1HRC
BL12NOBORUNOP BL104SEASONS

NOVA

BL01
↓

BL21

BL22ANNRI
BL23SENJU
BL18TAKUMIBL11BL05

RADEN
POLANOPLANET

DNA
BL02

↓iBIX

VIN ROSE
BL06

BL04

BL03

SPICA
BL09

S-HRPD
BL08

BL1913

Muon Facility MUSE @ MLF
S-LineH-LineAccommodate manyμSR experiments

Fundamental Science
with a large scaleinternational coll.

U-LineD-LineVery unique Ultra-Slow
Muon Beam

Mid-intensity beam line
For general use 14

Particle and nuclear physics at J-PARC
3GeV RCSCPV in Charged Lepton?

FX beamgµ-2/µEDM
new particle νs?

MLF

Hyper-nuclear physics

Neutron star
Strangeness in Nuclei
Role of strange quark in extreme high15density matter?

CPV beyond CKM
105MeVe−Flavor&CPV in charged lepton?
Search for µe conversion

q

Hadronμ− Hallqγ, Z’μCOMET（Hadron Hall）

2e

Experiments at MLF

16

Sterile neutrino search experiment: JSNS2(-II) Experiment(JSNS2) : 1MW x 3 years• 24m (near) detector only
• 3 long physics datataking in 2021-2023.
(~30% planned data)• Analyses are on-going.

MLF building (bird’s view)

Near detector @ 3rd floor(24m from target)

Detector @ outside
Of MLF building(48m from target)

Hg target＝neutronand ν source(JSNS2): near detector
17t GdLS fiducial(4.6m dia. x 4.0m height120 10” PMTs)

3GeV shortpulsed p beam

Search for neutrino oscillation : νµ  νewith 24m (JSNS2), 24m+48m (JSNS2-II)(JSNS2-II:
New far detector)
32t GdLS

Current JSNS2(6.2m dia, x
6.2m height~228 10” PMTs)

Globalfit indicated region

M. Dentler,etal., JHEP08010 (2018)

JSNS2-IICovers theglobal fit indicatedregion nicely.

(JSNS2-II): 1MW x 5 years• Proposal in 2020
(arXiv:2012.10807)• New far detector will
be added.
• 32 tons fiducial• 48m baseline.

• Good sensitivity forlow ∆m2• 2022/4:stage-2 (out of2) approval from J-PARC• Aim to start in 2024.

17

Statusν energy@ Hg targetνeνe

νµNear detector

Far detector

 Blind analyses
for sterile νsearch are onµ going 172 out of228 PMTs wereinstalled.
 All PMTs
except forveto region.

ν Observed νµfrom K+µ2
@ Hg target
Observed energy
by near detector

 Monochromaticenergy νfeedback to νinteractionmodels.
 Beam / detector
are working well.

 Rapid
progress onconstruction
 aim tostart datataking in2024.

© KEK-IPNS© KEK-IPNS

18

J-PARC muon g-2/EDM experiment
g-2

EDM

• Aim to reach• µ g-2: 450ppb• µEDM: 1.5e-19• Aiming for datataking from 2028
J-PARC MLF

muon g-2

J-PARC is the only experimentto check FNAL/BNL results.

Constructed in 2021Features:•••••

Low emittance muon beam (1/1000)
No strong focusing (1/1000) & good injection eff. (x10)Compact storage ring (1/20)
Tracking detector with large acceptanceCompletely new method (different from BNL/FNAL)

19

J-PARC muon g-2/EDM experiment
New radiation shields for beamline
extension (2022)

Muon cooling test (2022~)

Muon cooling + acceleration test (2024~)

The collaboration (114 members fro 10 countries)

20

study @ Muonic atom J-PARC MLF(1) Muonic X-ray measurement[Phys. Rev. Lett. 130, 173001 (2023)]
Goal : Verify strong-field QED with spectroscopy of muonic atom X-rays

Muonic atom

Key technology : Superconducting TES microcalorimeters

TES

Result : Proof-of-principle experiment with μNe atom
Outlook : scheduling the main experiment (μAr atom)in next February, 2024.

Electric field 40,000 times stronger
than that of normal atoms !

Excellentenergyresolution !

(2) Muonic Helium Atom HFS
Muonic Helium

Hydrogen-like atom similar
to muonium[2020B0333]

µHe
µHe
4 atm
Dn(µHe) = 4465.004(29) MHz

towards QED test in ultra-strong electric fields beyond
the Schwinger limit
by introducing new TES detector for hard X-rays
Goal : Verify strong-field QED with spectroscopy ofmuonic atom X-rays
Key technology : Same technique as with Mu used
to measure µHe HFS
Result :World record is achieved
Previous date: 6.5 ppm  Our experiment: 4 ppm

Outlook :Sensitive tool to test 3-body atomic systemand bound-state QED theory and determine
fundamental constants of the negative muon
Mar. 2021 magnetic moment and mass to test CPT with 2nd21generation lepton

Muon g-2 and muonium
These three quantities aremutually correlated. Only JPARC can close the triangle.

g-2µµ

PLB 815, 136154 (2021)

PRA 104, 020801 (2021)

FNAL
J-PARCmµ

J-PARC (MuSEUM)

Mu HFS

450 ppbmµ690 ppb(2017)  160 ppb(2018)  4 ppb

J-PARC, PSI

Mu 1S-2S

120 ppb  122ppb

DeeMe Experiment• Search for mu-e conversions in MLF muon target (Graphite)

Nucleus𝜇𝜇−𝜇𝜇 − + 𝐴𝐴, 𝑍𝑍 → 𝑒𝑒 − + (𝐴𝐴, 𝑍𝑍)• Will be conducted at J PARC MLF• Pulsed proton beams from 3 GeV RCS(fast extraction)

T2KNear Detector

3 GeV
Rapid Cycling Synchrotron(RCS)Materials and Life Science
Experimental Facility(MLF)
Hadron Hall•

Transport signal electrons by a newbeamline (H line) to the DeeMespectrometer.

•The DeeMe spectrometer consistsof 4 MWPCs and a bending magnet.

• 𝜇𝜇− production target = stopping target• SES ~10−13 (Carbon target, 1 year)• Detector commissioning has started.
• Momentum reconstruction successful.
• Data analysis on going.

23

Neutron lifetime experiment
The neutron lifetime differs significantly between measurement of decay and disappearance.
This discrepancy is known as the “neutron lifetime puzzle”. It is still an open question,
whether some errors of experiment, or indicating new physics.
Our first result+15
𝜏𝜏𝑛𝑛 = 898 ± 10stat −18
sys s

K. Hirota et al.
Prog. Theor. Exp. Phys. 2020, 123C02 (2020)
DetectInjectNeutron lifetime puzzle
9.5 s (4.6σ)

Cold neutron beam (polarized)

Disappearance
Storage method
Number of remaining neutrons

Decay
Beam method

1/eNeutronlifetimeTime

Neutron beam bunch(SFC) To solve the neutron lifetime puzzle, a newtype of experiment is on-going at a neutron
beam line in J-PARC.
Goal: measurement with ~1 s accuracy

24

Neutron Interferometer
Neutron interferometers can precisely measure interactions
with neutron as phase differences. The newly developed
multilayer interferometer with a pulsed neutron source canuse wide wavelength, simultaneously.
Oscillation in TOF

Phase shift with Si Oscillation by interference of neutrons were clearlyobserved (visibility ~70%).
 Phase shift by inserting sample in a path was measured.
→ successfully measured scattering length.
 Further wavelength extension is planned to increase
statistics by a factor of 20.

25T. Fujiie et al., arXiv:2308.01922

T-violation search using compound nuclei
P-odd and T-odd interactions can be largely enhanced in neutron induced compound nuclei
New T-violation search experiment based on optical behavior of neutron can be performed
without final state interaction. The fundamental study and development of polarized target
and neutron polarization device are ongoing.
𝐼𝐼

Polarized neutron𝜎𝜎𝑘𝑘𝑙𝑙 = 0,1, (2, . . )Development

Polarized taget

139La,131 Xe,117 Sn. . .

1. Optical Test

final-state interaction free

2. Enhancement

106 times enhancement

Enhancement mechanism

Polarized target : LaAlO3
K. Ishizaki et al. NIM A1020, 165845 (2021)

γ-ray yield

Neutron spin dependent asymmetry~30% 139La
polarization

3He neutron polarizer

T. Okudaira et. al. , NIM A 977, 164301 (2020)

Experiment withpolarized target + neutron
𝜎𝜎𝐼𝐼

T-even spin dependent
cross section:

w/ 139La polarization

T. Yamamoto et al. Phys. Rev. C. 101, 064624 (2020)~40% neutron
polarization

chromo-EDM

3. New Type of New Physics Search

Enhancement factor wasdetermined using (n,γ)
reaction→T-violation enhancement in139La+n : 106 times!

Spin dependent asymmetry𝜎𝜎 ⋅ (𝑘𝑘 × 𝐼𝐼)

T-odd cross section:𝜎𝜎 ⋅ 𝐼𝐼

w/o 139La polarization

Spin dependent cross sectionof 139La+n was successfully(2023)
observed ! T. Okudaira et al, arXiv:2309.0890526

Neutrino experiments

27

T2K (Tokai to Kamioka) experiment28

max. (kW) 540.961
POT total
3.82888e+21
nu2.17835e+21 (56.8927%)
nubar1.65053e+21 (43.1073%)

Evidence  Observation of νµ  νe(2011-2013)

Updated goals
 Measure CPV phase,contribution to mass hier.
determ.

Operation status 540kW operation achieved (2023)
 Delivered POT: 3.8e21 (nu:2.2/anu:1.7)

2010~ (Running)

T2K latest results (2022)
 3.6x1021 POT (2010~2022) analyzed
 World leading measurement of atm

param Large area of dCP excluded at 3s
 CP converving excluded at 90%
 Weak preference of normal ordering

29

30

T2K future : Explore neutrino/anti-neutrino difference with intenseneutrino beam & high precision measurements
31

New horn magnet

1x1x1cm3 scintillator cube x 2M
New target

Hyper-Kamiokande construction ongoing
Funding started from FY2019 supplementaly budget
Start operation in 202732



~ 10 times larger detectorBeam power

Aim to discover CPV and n decay etc
Assuming 1e7s/yr operation (~114d/y)

 Fiducial mass: SK22.5ktonHK 190kton
 0.5MW  1.3MW

Experiments
at HadronExperimental
Facility33

Hadron Experiment Facility
StrangenessNuclear Physics
Hadron Physics

K Rare Decay(CP violation）

Hadron Mass Shiftmu-e Conversion Search34

2/11

Origin & Evolution of Matter
Matter-Antimatter
Symmetry
matter dominated universe

Origin of Matter Creation𝑞𝑞�

CP violation
weak interaction
 new physics

𝑞𝑞
𝑞𝑞

formation of hadrons from quarks

𝑞𝑞

quark interactions
hadron mass-generation mechanism

𝑞𝑞

Matter in ExtremeConditions
dense matter in neutron stars

hadron interactions
hadronic many-body systems𝜦𝜦【Nuclear physics at Hadron Experimental Facility】
Elucidation of the property and origin of “generalized nuclear force” including strangeness
Mass measurement of Xi hypernuclei

Discovery of charge symmetry breaking
in the force between Lambda(Λ) and nucleon

伊吹イベント“Ibuki” event
5 HeΛΞ−15 CΞ

10 BeΛ

Establishment of scattering experiments
between strange baryon and proton
lifetime→ improve theSigma 0.1 nano sec
precision of
scattering angle
proton distribution
by x10 for the firsttime in 50 years

dσ/dΩ (mb/sr)→ confirm the force between Xi (Ξ) andnucleon is attractive
angle distribution of elastic
scattering between sigma(Σ) andproton

DataJ-PARC
Past exp
theoryquarkmodelcos θmesonexchange
model36

【Nuclear physics at Hadron Experimental Facility】
X10 tighter binding energy than nucleusp

K中間子束縛質量しきい値pΛと陽子の質量和

K−Production cross section

extremely compact (dense) and exoticnucleus

mass from decay particles (GeV/c2)

Precise measurement of X-rays from K− mesonic atoms
introducing superconducting transition-edge sensor(TES) microcalorimeters, the world’s best resolution
and the most accurate thermometer, to to the X-ray
measurement
X10 improvement
Energy shift (eV)Discovery of new nucleus including K− mesonJ-PARC
2022

X-ray measurement frommuonic atoms at MLF

37

KOTO experimentSearch for CP violating decay KLπ0ν𝜈𝜈̅SM pred. is very small ~3e-1138

 Sensitive to New Physics
Upp bound: 4.9x10-9 (90%CL) PRL 126,
121801 (2021) Editors’ Suggestionfurther accumulate physics data toward
the sensitivity better than 1x10-10NEW2023

New results from KOTO

Announced at KEK IPNS and J-PARC Joint Seminar on Sep.6, 2023

• Results based on data taken in 2021••

Single event sensitivity = 8.7×10-10
Expected number of backgrounds = 0.255

World-bestlimit
Breakdown of backgrounds

Next Step• KOTO continues taking physics data to achieve asensitivity better than 10-10.
• A next-generation experiment KOTO II with~100 times better sensitivity are being
39
considered.

KOTO prospects for future run•

The accumulated POT will be 10 times more in 3-4 years, assuming 60
days/year run.
 Will reach a sensitivity better than 10-1040

J-PARC E16 experiment• Aim to measure changes of hadron mass in thefinite density matter (nucleus)• Study process of the dynamical generation ofhadron mass
• Hadron mass is dynamically generated by QCD.
• Spontaneous breaking of chiral symmetry• Status• First beam in May/2020• Commissioning of new beam line and detectors in2020, 2021, 2023, 2024
• Physics runs in 2024 or 2025 (Need approval ofPAC)
Expected spectrum
Beamline(Full Statistics after BG subtraction)

MagnetProton Beam

41

COMET experimentµe conversion searchμ−+(A,Z)e−+(A,Z)
Very small O(10-54) in SM Discovery = New Physics!


COMET HallFirst commissioning in FY202242

First beam to C-line for COMET!!
First beam on target @ Feb.9,19:44:30, 2023

[μsec]

43

Hadron Experimental Facility Extension (HEF-ex) project

Present facility

1 production target (T1) +2 charged beamlines (K1.8/1.8BR, High-p)
1 neutral beamline (KL)
1 muon beamline (COMET)

1 new production target (T2) +4 new beamlines (HIHR, K1.1/K1.1BR, KL2, K10) +2 modified beamlines (High-p (π20), Test-BL)

KEK-PIP 2022 Priory Number 144

Future J-PARC Heavy Ion program
Explore the QCD phase diagram• Facility Upgrades Plan••

New accelerator injectorNew spectrometer•Phase1:• Staging approach••••Beam Intensity: 108 Hz for Au
Upgrade of the current E16spectrometer
New LINAC and reuse of KEK-PSbooster

Phase 2••

Beam Intensity: 1011 Hz
New booster and new spectrometer

EOS of Neutron Star
New state of the matter
Quark Phase
Color Super conductivity
Hadron physics in finite density
Schematic view of final spectrometer

45

Summary

46

J-PARC is the world leading intensity frontier proton accelerator
research complex
 3GeV RCS/MLF: reached at 840kW stable operation
 30GeV MR
 FX: 515kW/SX64kW achieved before major upgrade Upgrading toward 1.3MW
 750kW (single shot) acceleration succeeded aft. PS upgrade

J-PARC is unique facility covering wide range of research fields
 Particle, nuclear physics, material and life sciences and industrial

applications, Archeology, planetary scienceMany exciting projects are being conducted/prepared

KEK’s next highest priority project is HD hall extension

Stay tuned