J-PARC muon g-2/EDM experiment
Yutaro Sato
N iig a t a U n ive rsit y
O n b e h a lf o f t h e J - P A R C mu o n g - 2 /EDM c o lla b o ra t ion

A u g . 3 0 th 2 0 2 2

CIPANP2022

2Muon g-2 and EDM
Muon anomalous magnetic moment (a μ , g-2)
⚫ Deviation of g-factor from the prediction of Dirac equation for fermions.
– 𝑎𝜇=𝑔 −22=𝑎 𝜇 𝑄𝐸𝐷

QED+ 𝑎 𝜇 ℎ𝑎𝑑

Had.

+ 𝑎 𝜇 𝑤𝑒𝑎𝑘

EWlbl

e.g. SUSY

Hadron𝛾Hadron+ 𝑎 𝜇 (𝑁𝑒𝑤 𝑃ℎ𝑦𝑠𝑖𝑐𝑠 )𝜇෤𝑍⚫ 4.2σ deviation between the SM prediction and measurements– σ SM : 0.37 ppm [white paper]– σ exp : 0.35 ppm [BNL+FNAL]

Electric Dipole Moment (EDM)⚫ If non-zero EDM exists, it means T -violation. → CP-violation⚫ Exp. upper. limit : 𝑑 < 1.8 × 10 −19 𝑒 ∙ cm(95% C. L. ) by BNL E821.
→ A new experiment to measure muon g -2 and EDM at J -PARC𝜇෤𝜒ǁ 0PRL 126, 141801 (2021)

3Experimental Approaches
momentumspin⚫ In uniform B -field, muon spin rotatesahead of momentum due to g -2 ≠ 0.
𝝎 = 𝝎𝒂 + 𝝎𝜼B𝒆𝟏𝜷×𝑬 𝜼𝑬=−𝒂𝝁 𝑩 − 𝒂𝝁 − 𝟐+𝜷×𝑩+𝒎𝝁𝜸 −𝟏𝒄𝟐𝒄g-2 term

ωaEDM term

J-PARC E34
Simulation
J-PARC E34
Simulation

∝ EDM

4

Experimental Approaches (BNL, FNAL)
momentumspin⚫ In uniform B -field, muon spin rotatesahead of momentum due to g -2 ≠ 0.

0

𝝎 = 𝝎𝒂 + 𝝎𝜼𝒆𝟏𝜷×𝑬 𝜼𝑬=−𝒂𝝁 𝑩 − 𝒂𝝁 − 𝟐+𝜷×𝑩+𝒎𝝁𝜸 −𝟏𝒄𝟐𝒄g-2 term
BNL E821 & FNAL E989
•Magic momentum
𝛾 = 29.3 (𝑝 = 3.1 GeV/𝑐 )•Weak electric focusing.

𝒆𝜼𝑬
𝝎=−𝒂 𝑩+𝜷×𝑩+
𝒎𝝁 𝝁𝟐𝒄

EDM term

B5Experimental Approaches (J-PARC)
momentumspin⚫ In uniform B -field, muon spin rotatesahead of momentum due to g -2 ≠ 0.

0

𝝎 = 𝝎𝒂 + 𝝎𝜼0B

𝒆
𝟏
𝜷×𝑬 𝜼
𝑬=−𝒂𝝁 𝑩 − 𝒂𝝁 − 𝟐+𝜷×𝑩+
𝒎𝝁𝜸 −𝟏𝒄𝟐𝒄g-2 term

EDM term

BNL E821 & FNAL E989

J-PARC E34••

No electric field•

Very weak magnetic focusingMagic momentum
𝛾 = 29.3 (𝑝 = 3.1 GeV/𝑐 )•Weak electric focusing.

𝒆𝜼𝑬
𝝎=−𝒂 𝑩+𝜷×𝑩+𝒎𝝁 𝝁𝟐𝒄

𝝎=−𝒆𝒎𝝁𝒂𝝁𝑩 +𝜼𝟐𝜷×𝑩
𝑝 = 3 0 0 Me V / 𝑐→ Different systematic uncertainty.

→ Clear separation of 𝝎 𝒂 and 𝝎 𝛈 .

Reaccelerated thermal muon beam
protonπ+μ+6

Conventional muon beam
Emittance ~ 1000π mm・mraddecay⚫ No requirement of strong beamfocusing by an electric field

Cooling andacceleration

pion
production

Strong focusing with electric field
Muon loss
Pion background➢ Weak focusing B -field.
⚫ Free from magic momentum of 3.094 GeV/cμ+
Reaccelerated thermal muon beam
Emittance ~ 1π mm・mrad

Free from any of the above➢ Lower momentum beam of 300 MeV/c– Compact storage ring with excellent uniformity (Δ~0.1 ppm)
– Full tracking detector for decay positron

7J-PARC muon g-2/EDM Experiment① Muon Beam Lineand experimental area

② Thermal muon

①Surface μ +③ Muon linac④ Injection⑤ Storage⑥ Detector⑥Positron detector⑤Storage

Initial goalg-2 ~ 0.45 ppm
EDM ~ 10-21 e・cm

Final goal→ 0.1 ppm

J-PARC Proton Accelerator Research Complex (J-PARC)

8Linac(400 MeV)

Ibaraki, Japan★

νprotonRapid Cycle
Synchrotron(3 GeV)

(to Kamioka)

Material and Life Science
Facility (MLF)
Main Ring(30 GeV)

Hadron Hall
Bird’s eye photo in January of 2008

① Muon Beam Line and Experimental Area

9

⚫ Construction of H -line up to H1 area has been finished.
⚫ The first beam of H -line was detected on Jan. 15, 2022.

Muon production
targetNeutron area

Proton beam

H1H2Quadrupoles

H-linebendExtension(H2 area) for g-2/EDMto be constructed in FY2022

H1 areafor MuSEUM(Mu-HFS) &DeeMe(μ-e conversion)
Beam delivered in Jan 2022

SolenoidSlitSeparator

① Muon Beam Line and Experimental Area

10

⚫ The extension building (H2) is being ready for construction.

Making a vacant lot

H2MLF
H1

Ground survey
Proton beam

② Thermal Muon Production

11⚫ Surface muon ( 2 7 M e V / c ) is stopped at an target andmuonium ( μ + e - ) is emitted.
⚫ A muonium is ionized by laserand thermal muon beam ( 2 5 m e V / c ) is produced.
⚫ Muonium production target : Laser ablated Silica aerogel– ×10 more muonium emission rate compared to flat silica aerogel.
– Various laser -ablated structures and aerogel materials were studied.
@PTEP 2020 (2020) 123C01

Drilled Aerogel
Flat Aerogel

Mu yield

Events/3×108 muons@PTEP 2014 (2014) 091C01

×~10Time (μs)

Opening fraction on the emission face

② Thermal Muon Production⚫ Surface muon ( 2 7 M e V / c ) is stopped at an target andmuonium ( μ + e - ) is emitted.
⚫ A muonium is ionized by laserand thermal muon beam ( 2 5 m e V / c ) is produced.

Laser-resonant ionization methods⚫ Original plan : an intense 122 nm (Lyman -α) laser– Efficient single photon excitation– Challenging 100 μJ Lyman-α laser development⚫ Plan B : ionization scheme with 244 nm laser– Established laser technol ogy– Collaboration with the muonium1S - 2S

spectroscopy measurement experiment12

③ Muon Acceleration

13

World 1 st accelerationof muons by RFQ⚫ Thermal muons are reaccelerated up to 300 MeV/c by muon LINAC.

– Fast acceleration to avoid muon decay loss
– No emittance growth.
⚫ Different cavity to realize fast re -acceleration through wide β region.
⚫ World’s 1 st acceleration of μ in Mu - ( = μ + e - e - ) in 2018 by RFQ– Accelerati on of thermal μ is planned in 2023 by RFQ

Phys. Rev. AB 21, 050101 (2018)

③ Muon Acceleration

14⚫ The rest of acceleration cavities are designed
and their performances are being evaluated with prototypes.
– IH-DTL : Fabrication of real -type was completed.
– DAW-CCL : 1 st tank is being fabricated.

– DLS : prototypes will befabricated FY2022⚫ R&Ds for beam monitor system

is also ongoing.
–Phys. Rev. Accel. Beams, 23,022804(2020)

IH-DTL (real-type)

1 st tank of DAW-CCL

④ 3D-Spiral Beam Injection

15⚫ For injection of muon beam into compact storage ring,
3D-spiral injection scheme has been invented.
– Smooth connecti on between injection and storage regions.
– Pulsed magnetic kicker to guide muon beam into stable orbit.
– Weak-focusing magnetic field to control muon beam within a few cm.
H. Iinuma et al. NIMA 832 (2016) 51
Upper plate (pure iron)channelPole tip

Return yoke (pure iron,cylindrical shape)

Main coil➢ Higher injection efficiency : ~85%Injection
regionStorage region（weak focus）¼ model⇔ 3-5% @BNL E821 [ P R D 7 3 0 7 2 0 0 3 ( 2 0 0 6 ) ]④ 3D-Spiral Beam Injection⚫ Demonstration experiment of the injection schemewith low momentum electron beam is progressing well.
– Visualize 3D spiral beam traject or y with CCD camera.

⚫ Prototypes of kicker was fabricated and will be demonstrated.
Demonstration experiment setup

Prototypes of kicker

16

⑤ Muon Storage Magnet

17⚫ 3T MRI-type superconducting solenoid magnet is used to store a muon beam.

Good field region
100 mm

2.9 m

66 cm

30 mm

M. Abe et. Al., Nuclear Inst. and Methods in Physics Research A890, 51 (2018)

25 ppb/line

⑤ Muon Storage Magnet⚫ High uniformity of the magnetic field is achieved by shimming.
– Local uniformity of 1 ppm was confirmedwith the magnet used in the MuSEUM experiment.

⚫ High precision NMR probes are used for field measurement.
– Cross-calibrati on is underway in a joint research project
between Japan and the US.

– An accuracy of 15 ppb has been achieved.

After shimming with Fe, Ni, Putty (0.17 ppmpp)

18

Cross-calibration of FNAL
and J-PARC field probes

⑥ Positron Detector⚫ Positron tracks are measured by Silicon-strip detector.

19

Event display with 25 muons– Positrons with a momentum of 100 -300 MeV/c– High hit rate capability (6 tracks/ns)
and stability over early to late rate changes (1.4 MHz → 10 kHz)– Design optimized for pulsed beam.

Quarter vane moduleReconstruction efficiency
490.5 mm

32 ASICs

66 cm

4 sensors
208 mm⑥ Positron Detector

20⚫ Major components are in or completed the mass -productions.
⚫ Prototype module is being assembled.
Readout ASIC (SliT)⚫ Silterra 180-nm CMOS process⚫ Binary output with samplinginterval of 5 ns
⚫ Mass-production : done
IEEE TNS 67, 2089 (2020)

Flexible printed circuit boards⚫ Made by Fujikura Ltd.
⚫ Mass-production : done

Silicon-strip sensor⚫ Made by Hamamatsu Photonics K.K., S13804⚫ Strip pitch : 190 μm⚫ Mass-production : ongoing

Quarter vane module
Rigid printed circuit boards⚫ Prototypes were fabricated and being tested.

Statistics Estimation

21Prog. Theor. Exp. Phys. 2019, 053C02⚫ Overall efficiency : 1.3 ×10 -5⚫ Assuming 2.2×10 7 sec (~255 days) of data taking,total number of reconstructed e + is 5.7 ×10 11 .

Expected uncertainties
Stat.

Syst.

δ aμ450

<70

δ EDM

1.50.36[ppb][10-21 e・cm]➢ 2-year running will reach the BNL precision of a μ .
➢ Systematic uncertainties will be much smaller than the statistical ones.

Schedule

22Now!

Reach the BNL precisionin ~2-year running

23

J-PARC Muon g-2/EDM Collaboration
110 members from Canada, China, Czech, France, India, Japan, Korea, Netherlands, Russia, USA

New
Welcome University of Groningen
Domestic institutes：
Kyushu, Nagoya, Tohoku, Niigata, Tokyo, Ibaraki,
RIKEN, JAEA, etc.

KEK: IPNS, IMSS, ACC, CRY, MEC, CRC

Summary⚫ J-PARC muon g-2/EDM experiment aims to measure muon g -2 and EDM
with a method different from BNL/FNAL experiment.
– Low emittance muon beam with no strong focusing.
– MRI-type storage ring with a good injection efficiency and high uniformity of local B -field.
– Full-tracking detector with large acceptance⚫ The experiment is getting ready for realization.
– Construction of new muon beam line “H -line”– R&Ds of the subsystem is going well.

⚫ Expecting data taking from FY2027.

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