The J-PARC muon g-2/EDM experiment
Kazuhito Suzuki
Kobayashi-Maskawa Institute, Nagoya University
On behalf of the J-PARC muon g-2/EDM collaboration
2021/6/28

Muon g-2 theory initiative workshop

1

Total fundamental factors
TotalsMuon g-2 and EDM (1)

%%%
544

25
462

Bk)and Bq .—Two fast transients induced by the dynam• Muon anomalous magnetic moment (aμMagnetic
DipoleMoment
ics of charging the ESQ systemand firing
the SR
kicker− Deviation of gμ from “2”, the prediction ofmagnet slightly influence the actual average field seen by
the beam compared to its NMR-measured value as
Dirac equation for fermions.
described above and in Ref. [61]. An eddy current induced
g: gyromagnetic
ratio by the kicker
locally in the vacuum
chamber structures− Precisely calculated in the SM and measured
system produces a transient magnetic field in the storage
in the BNL+FNAL experiments.
volume.
A Faraday EW
magnetometer Had
installed between the
QEDNP?
kickerplatesmeasuredtherotationofpolarized
light
in
a
➢ δSM: 0.37 ppm (“White paper”)
terbium-gallium-garnet crystal from the transient field to➢ δexp: 0.35 ppm (BNL+FNAL)
determine the correction Bk .

+− 4.2σ discrepancy between the SM andmeasurements.

PRL 126, 141801 (2021)
Physics Reports 887 (2020) 1–166“White paper”: Phys. Rep. 887 (2020), 1-166.
Contents lists available at ScienceDirect

Physics Reports
journal homepage: www.elsevier.com/locate/physrep

The anomalous magnetic moment of the muon in the Standard
Model
T. Aoyama 1,2,3 , N. Asmussen 4 , M. Benayoun 5 , J. Bijnens 6 , T. Blum 7,8 ,⇤M. Bruno 9 , I. Caprini 10 , C.M. Carloni Calame 11 , M. Cè 9,12,13 , G. Colangelo 14 , ,
15,16
17
12
18 ,⇤
19
F. Curciarello, H. Czyª , I. Danilkin , M. Davier, C.T.H. Davies ,⇤⇤M. Della Morte 20 , S.I. Eidelman 21,22 , , A.X. El-Khadra 23,24 , , A. Gérardin 25 ,
26,27
28
29
D. Giusti, M. Golterman , Steven Gottlieb , V. Gülpers 30 , F. Hagelstein 14 ,M. Hayakawa 31,2 , G. Herdoíza 32 , D.W. Hertzog 33 , A. Hoecker 34 ,⇤M. Hoferichter 14,35 , , B.-L. Hoid 36 , R.J. Hudspith 12,13 , F. Ignatov 21 ,
37
,
8
40,41
2021/6/28
Muon g-2
theoryinitiative workshop
2
T.
Izubuchi, F. Jegerlehner 38 , L. Jin 7,8 , A. Keshavarzi 39 , T. Kinoshita
,
36
21
42,43
14
26,37 ,⇤
B. Kubis , A. Kupich , A. Kup±¢, L. Laub , C. Lehner, L. Lellouch 25 ,FIG. 4. From top to bottom: experimental values of aμ from
I. Logashenko 21 , B. Malaescu 5 , K. Maltman 44,45 , M.K. Marinkovi¢ 46,47 ,Muon g-2 and EDM (1)ʼ• Muon anomalous magnetic moment (aμ)

Magnetic Dipole Moment− Deviation of gμ from “2”, the prediction of
Dirac equation for fermions.
g: gyromagnetic ratio− Precisely calculated in the SM and measured
in the BNL+FNAL experiments.

QED

EW

Had

➢ δSM: 0.37 ppm (“White paper”)NP?

+➢ δexp: 0.35 ppm (BNL+FNAL)− 4.2σ discrepancy between the SM andmeasurements.

• One of the best probes for New Physics(NP) beyond the SM.
− Need a new experimental approach as well as
an improved precision.

2021/6/28

P. Koppenberg,
http://www.scholarpedia.org/
Muon g-2 theory initiative workshop
article/File:AnomaliesPlot.png

3Muon g-2 and EDM (2)• Muon anomalous magnetic moment (aμ)

Magnetic Dipole Moment− Deviation of gμ from “2”, the prediction of
Dirac equation for fermions.
g: gyromagnetic ratio− Precisely calculated in the SM and measured
in the BNL+FNAL experiments.

Electric Dipole Moment➢ δSM: 0.37 ppm (“White paper”)➢ δexp: 0.35 ppm (BNL+FNAL)− 4.2σ discrepancy between the SM andmeasurements.

• Electric Dipole Moment (EDM, dμ)• One of the best probes for New Physics − Can be measured in parallel with a .
μ(NP) beyond the SM.
− Need a new experimental approach as well as
an improved precision.

− dμ

0 indicates T-violation, hence CP-

violation, in the lepton sector.
➢ SM: 2x10-38 e•cm,➢ Exp: < 1.8x10-19 e•cm (90% C.L. in BNL
E821)− Another probe for NP.
2021/6/28

Muon g-2 theory initiative workshop

4Experimental approach (1)ω# =ω
#a + ω
#η
#
&
'(
$
%
#
#
1
β# × EηEe###aµ B − aµ − 2
+
β ×B+
.
=−
m
γ −1
c
2
c

motion (ωc),spin(5)
precession (ωs)(6)

In a uniform B field (top
ω
(=
ω
‒
ω
)
ω
# and γ ηa due tosg − 2cand EDM. βview in lab. frame)and ω# η are precession vectors
are the velocity and Lorentz
the muon,E34
respectively.
E34 simulation
simulation
previous g − 2 measurements, the energy of the muon was chosen to cancel the term ofwhich allowed for electrostatic focusing in the storage ring without affecting the muon spinon to first order. A focusing field index of n = 0.12–0.14 was used, which was necessaryn the muons captured from pion decay. In this proposed experiment, we greatly reduce therequirement in the storage ring by using a reaccelerated thermal muon beam with a factor
smaller beam emittance. Very weak magnetic focusing with a field index of n ∼ 10−4 iso store the muon beam, using no electric field for focusing. Under this condition, Eq. (6)o2021/6/28"*
initiative workshope ) # Muonη !g-2 theory
# .
ω
# =−
aµ B +
β# × B5(7)06729 by High Energy Accelerator Research Organization(KEK) user on 22 June 2019

magnet and the muons orbit in the uniform magnetic field. The spin of the muon precesses
gnetic field. With the non-zero and positive value for g − 2, the muon spin direction rotates
an the momentum.
• Measure the “beat” frequency (ω)# and electricin precession vector with respect to its momentum in a static magnetic field B
cyclotron
to[16–21]
extract aμ and η.
given as=

506729 by High Energy Accelerator Research Organization(KEK) user on 22 June 2019

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e-abstract/2019/5/053C02/5506729 by High Energy Accelerator Research Organization(KEK) usé g-factor and η is a corresponding factor for the EDM. The experiment stores spin-polarizedof the experiment
magnet and the muons orbit in the uniform magnetic field. The spin of the muon precesses
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definedaby
andthe relations
η.
are definedby the value
relationsµ Withfield.
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agµ =
# and
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inprecession
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respectively.
spin vectorHere,of thegmuon,isrespectively. Here, g isor
actor
andforηωisa=corresponding
EDM.
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spin-polarized
The experiment stores spin-polarized#theω#a + ω# η experiment(5)#field.
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g
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the
positive
muon
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value
directionforg−rotates
2,
the
muon
spin
directionaµ B − aµ − 2+
β ×B+. rotates(6)=−
p= 3.09 GeV/c , B=1.45 T
m
γ −1
c
2
c
omentum.
# in# and electric
ossionits momentum
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its momentum
field Banda static
electric
magnetic field B#and ω# η are precession vectors due toand γ are the velocity and Lorentz
0 g − 2 and EDM. •β Items
as [16–21]
related to the major
the muon, respectively.
BNL E821 approach
γ=29.3 (p=3.09 GeV/c)
uncertainties
previousg−
was chosen to cancel
the
ω
# =ω
#a + ω
# η 2 measurements, the energy of the muon(5) systematic(5) term of (BNL)'( in the storage& ring without'( affecting the muon spin
which allowed
focusing$&% # for electrostatic%
Strongfocusing E field,−## β# × E
#
#
#×E
1
1
β
η
E
η
E
e
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A
which was(6)necessary#+#field# +was used,− focusing
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β# ×
(6)B
. large= first− order.
2
2
➢
for
the
phase-space
beam,
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m ccaptured
2 fromγpion− 1decay.
ccIn this 2proposed experiment,cwe greatly reduce the
B field
non-uniformity,requirement in the storage ring by using a reaccelerated−thermalmuonbeam with a factor
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E989
#
#
are
o g precession− 2 and
EDM.
vectors
β anddueVery
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andEDM.
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and ofLorentz
smallerbeam
emittance.
magnetic
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− Detectoron,respectively.
o storethe muon beam, using no electric field for focusing.
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soenergyg − 2 ofmeasurements,
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the muon
the term
was ofchosen to cancel the term of
singowedinfortheelectrostatic
storage ringfocusing
without affecting
in the storage
themuonring without
spin affecting the muon spin
2021/6/28
Muon g-2 theory initiative workshop
6)!
"*e whichη necessaryndex
st order.
of nA=focusing
0.12–0.14
field
was
index
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of
n =# 0.12–0.14
was# used, which was necessary# wasExperimental approach (3)==A new measurement with completely different systematics is possible.
2021/6/28

e )Muon g-2 theory initiative workshop

#

η!

#

#

"*

7

506729 by High Energy Accelerator Research Organization(KEK) user on 22 June 2019é g-factor and η is a corresponding factor
stores &spin-polarized'(# for the$EDM. The experiment%# theηmuon precesses#
1 The spinβ# × ofE
E
magnet and the muons orbit in the euniform
magnetic field.
###
Siliconaµ B − aµ − 2
+
β ×B+
.
(6
=−
c spin 2direction rotatescgnetic field. With the non-zero andmpositive value for gγ −−
2, 1the muon
Trackeran the• momentum.
Eliminate the βxE term for simplification.
# and
# and
ω
# a andω# η areprecession
vectors
due
to
g
−
2
and
EDM.
β
γ are
the velocity and Lorenin precession
vectorwithrespect
to its(pmomentuminastaticmagneticfield
Belectric“Magicmomentum”=
3.1
GeV/c).
−Hereμof therespectively.
given as[16–21]−factor
Nearlynomuon,E field
with “ultra-cold muon beam”
In the previous g − 2 measurements, the energy of the muon was chosen to cancel the term o
ω
#β#=
#E,
ω
# η allowed for electrostatic focusing
(5)
#a +
×ω
which
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2
to=containmuons
capturedfrompion
decay.
proposed
m
γ −1
c
2
c
Supermuon
Precision
Storage
Magnetfocusing requirement in the storage ring by using a reaccelerated thermal
beam
with
a facto(3T, ~1ppm local precision) −4of
adue
of precession
1000 smallerbeam
emittance.
Very
weak
focusingwithfield index of n ∼ 10and ω#•η Extraction
arevectors
to g − 2 andEDM.
β# magnetic
and γ are thevelocity
andaLorentz
μSmall-emittance beam,
enoughto store the muon beam, using noJ-PARC
electric
field for focusing.− Under
this condition, Eq. (6the muon,
respectively.
approach
E = 0 at any γ
NMRfocusing B field,− Weakprevious reducesg − 2 measurements,
theprobe
energy of the muon was chosen to cancel theterm oftoCompact
which allowed for electrostatic focusing in the storage ring without affecting the −muonspin NMR-type)!
"*(ωp: Larmor freq.
eηused, which
storage magnet withon to first order. A focusing
field index of nω==0.12–0.14
was# .was necessary
#
#×B
#
−
a
β
(7
B
+
µ
of a free proton)
m experiment,
2
excellentn the muons captured from pion decay. In this proposed
we greatly reduce
the uniformity(μp: proton magnetic
requirement in the storage ring by using a reaccelerated thermal muon beam with(Δ~0.1
a factor ppm),
J-PARC
E34
moment)4/22a field index of n ∼ 10−4 issmaller beam emittance. Very weak magnetic focusing with− Silicon strip detector
Mu hyperfine
o store the muon beam, using no electric field for focusing. Under this condition,with
Eq. tracking(6)
capability.
splitting (MuSEUM)oJ-PARC muon g-2/EDM experiment• Small-emittance muon beam, therefore, no strong focusing(E≃ 0) and no momentum constraint (p=300 MeV/c).
Proton beam
• MRI-type compact storage magnet with existing technology,( 3 GeV, 1 MW)
high local-field uniformity, and good injection efficiency,(Sub)surface muons • Full-tracking capability with large acceptance.
(3.4 MeV, 27 MeV/c,
Δp/p~5% (rms))

H-lin
e in
Muonium (μ+e- or Mu)
production target

Thermal muons(25 meV, 2.3 keV/c)

Small-emittance muons(212 MeV, 300 MeV/c, Δp/p~0.04% (rms),
εxnorm~0.33π mm mrad (rms))
Muon linac

MLF

at J-

PAR
C

Photoionization
lasers2021/6/28

Muon source

Muon g-2 theory initiative workshop

3D spiral
injection

MRI-typestorage magnet(3 T, φ66-cm orbit)

Silicon-strip detector
for positron tracking
8Japan Proton Accelerator
Research Complex (J-PARC)
Tokai, Ibaraki
LINAC(400 MeV)ν(To Kamioka)

Rapid Cycle
Synchrotron(3 GeV)pμn

H2 area(Under designing)

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

2021/6/23

KMI Topics

9

Hadron Hall

Surface muon beamline (1)Proton beam
( 3 GeV, 1 MW)• (Sub)surface muons− μ+ decayed from π+ stopped at or near(Sub)surface muons(3.4 MeV, 27 MeV/c)the target surface.
− 100%-polarized and monochromatic
66 cm(not for the subsurface muons).

H-lin
e in

MLF

at JPARC• H-line at J-PARC MLF− Double pulse structure at

100ns (FWHM)

25 Hz repetition,− Intensity: ~108 μ+/s.
2021/6/28

Muon g-2 theory initiative workshop(25 Hz)10

Surface muon beamline (2)• The beamline commissioning will start in November 2021.
To H1
Quadrupoles
Proton beam

H-lin

e

To neutron
area

Graphite target
(π→μ)

To H2

Bend
H1

Solenoid
H2

2021/6/28

H1 area:− Commissioningin Nov. 2021.

H2 area:− Under construction,− Beam delivery in FY2023.

Muon g-2 theory initiative workshop

Slit

Separator

11Surface muon beamline (3)• The extension building is being readyfor construction.
Muon g-2/EDM
experiment at J-PARCµ+(4 MeV)

J-PARC 物質・⽣命科学実験施(MLF)

Preparation for construction in 2020

H-line extension building:− Under designing and ground surveys,− Apparatus will be installed by FY2024.

m

µ+
(

25

uo

n

co

o li

me
V)

ng

m

uo

nL

µ+
(2

Preparation for construction in 2020
IN

AC

10

Me
V)

in

0.66 mjec
ConBTstr
utiocntion site

E34

Construction sitemuonstoragemagnetmuon storage magnet☑ Ground leveling 11
Detailed designingsurvey of en7re area
☑ Ground levelingsurvey of en7re area

Making a vacant lot

2021/6/28
Proton beam

Muon g-2 theory initiative workshop☑ofPar7alremoval of trees☑ Par7al removal
trees

Ground survey

12☑ Geotehcnicalsurvey☑ GeotehcnicalsurveyThermal muons (1)Thermal muons(25 meV, 2.3 keV/c)
66 cm

H-lin
e in

MLF

at JPARC• Muonium (μ+e-, Mu) production- Cooling and diffusion in a form of Mu,- The polarization reduces to 50% due to thehyperfine states in the Mu formation,- Thermalization at room temperature,- Diffusion and emergence into vacuum
following the Maxwell-Boltzmann distribution.
2021/6/28• Laser-resonant ionization- To produce thermal muons,- Using a high-power pulse laser.
- 122 nm (Lyman-α) for μ-microscope.
- 244 nm for Mu 1S-2S spectroscopy.

Muon g-2 theory initiative workshop

13

Thermal muons (2)• Silica aerogel (SiO2) for the muonium
production target− Porous, similar to the silica powder.
− Better handling in a beamline.

Pitch (p)• Laser ablation on the surface
improved the Mu emission rate.

φ0.1 mm, p0.5, 0.3, 0.15 mm
50 x 50 mm2, 8 mmt-3Rvac
Mu [10 ]− The ablation structures could promote thediffusion.
− Applicable to reach the BNL precision in~2-year running.

Ablation
30 x 30 mm2
GroovesContinuous

Target size (typ.)35
30

Prog. Theor. Exp. Phys.
123C01 (2020)25●w/ ablation◯

20

w/o ablation

Aerogel (grooves)
Aerogel (holes)
Aerogel (flat)
Silica plate
PMSQ (holes)
PMSQ (flat)
Aerogel in Ref. [15] (holes)
Aerogel in Ref. [15] (flat)

15

8-10x

10

Prog. Theor. Exp. Phys.
091C01 (2014)

502021/6/28

0Muon g-2 theory initiative workshop

0.2

0.4

0.6

0.8

Hole opening fractionvac

1
Fopen14[a.u.]

Thermal muons (3)• Laser-resonant ionization needs
to be examined.
μ+ + e-Unbound355 nm
pulse

Mu 2P

Mu 2S

122 nm
pulse
Mu 1S

Mu 1S

μ+ + e- Ionization Spectroscopy
244 nmpulse
244 nmpulse
244 nmpulse

355 nmpulse
244 nmCW
244 nmCW

Mu 1S-2S
spectroscopy(MLF S-line)

Excitation
process

122 nm (VUV)→difficult handling
One-photon exc.
→higher prob.

244 nm (DUV)→easier handling
Two-photon exc.
→lower prob.

Technologies

Need challenging
developments.

Established ones
available.

Ionization rate
(expected under acertain condition)

3% at 3 μJ.

1.6% at 200 mJ(x multi-pass amp.).

Project− A first priority in this and next years.
UnboundTransmission
μ-microscope(MLF U-line)

Wavelength− A dedicated beam will be available at MLF S-line from November 2021
for the Mu 1S-2S spectroscopy.
Laser-resonant ionization
S2 area
H2

Slow muon beam line (SMBL)
μH1

Micro-channel
plate (MCP)

Ultra-slow(thermal) μS2of H atoms/compounds

Surface μLaser hut

2021/6/28

Ionization laser(244 nm)Muon g-2 theory initiative workshop

15

structure (DLS) traveling-wave linac is used when β is greater than 0.7 (42 MeV) [28]. The
details of each acceleration cavity are described below.

Muon linac (1)Table 8Output beam parameters of the DLS.

αx

Small-emittancemuons
β [mm/mrad]
ε [π mm mrad, rms, normalized ](212
300 MeV/c,
α MeV,
0.7 66 cm
β [mm/mrad]
-5)
Δp
/p~10
ε [π mmTmrad, rms, normalized ]xx

β = 0.01

0.08

y

0.3

y

y

z

MLF

Fig. 3εz [π MeV deg, rms, normalized ]Transmission
Transient time
Survival rate
Transmission total

Configuration of the muon linac.

at JPARC

2.2. Initial electrostatic acceleration

ε[π mm mrad]

H-lin
e in

αz

Muon linac
β [deg/MeV]

Output
-1.9
0.86
0.331
-3.3
1.5
0.211
0.07
150
1.94
99.9%
30 ns
99%
99%

0.94

• AccelerationXof theIn frontof thethermal
RFQ, theremuons
is an electrostatic lens called a Soa lens [29], which accelerates
and theextracts
the thermalgrowth.
muons.
suppressing
emittance

0.4

Y

Figure 4 shows
schematic- From p-like acceleration
to ae-likeone. view of the Soa lens. The Soa lens consists of two meshelectrodes and three cylindrical electrodes. The first mesh electrode (target mesh) covers thedownstream surface of the silica aerogel target.0.2The laser ionization
the
DAW CCL region is between
DLS
IH-DTLtarget mesh and second mesh electrode (S1). The voltage
applied to the target
mesh and S1
requirement
RFQ=1.5RFQ.
π mm mradis set to 5.7 and 5.6 keV, respectively, corresponding to the input energy ofεtotaltheThe
dimensions of the electrodes are designed to cover0 the primary surface muons (rms size of 31
0
10
20
30
directions, respectively [30]) and to provide
2021/6/28 mm and 14 mm in the horizontal
Muon g-2 andtheoryvertical
initiative workshop
16 a Z[m]sufficient extraction efficiency for ultra slow muons.
The voltage applied to other electrodes
Fig. 15 Emittance evolution from the RFQ entrance to the linac exit.

structure (DLS) traveling-wave linac is used when β is greater than 0.7 (42 MeV) [28]. The
details of each acceleration cavity are described below.

Muon linac (2)











w-power test w/ RF coupler$

The fabrication of the RF coupler for the proto-IH• RFQ• IH-DTL
had
been completed in Mar. 2021.
Fig. 3 Configuration of the muon linac.
Worldʼs first
RFchecked
accelerationof μ (in Mu-).
− Prototype: under extensive tests.
In the−low-power
test, wethe cavity
performancew/ RF coupler,
as a resonant− RF acceleration
ofsuckthermal
μ is planned in RF−coupler
Real IH-DTL: to %be fabricated in FY2021.
- made by copper
frequency,
Q-value,andcoupling
constant.
FY2022.
2.2. Initial electrostatic acceleration
77D-N Reducer

Ø23

370

76

.9

In front of the RFQ, there is an electrostatic lens called a Soa lens [29], which accelerates
Proto IH-DTL
and extracts the thermal muons.VNA(1/3 model)
Figure4 shows a schematicviewof the Soa lens. The Soa lens consists of two mesh
(Vector Network
Analyzer)
RF window
coupler
electrodes and three cylindrical electrodes. The first mesh RF
electrode(target mesh) covers thedownstream surface
ofantenna
the silica aerogel target. The laser ionization region is between
the
Loop
&
target mesh and second
meshelectrode (S1). The voltage applied to the target
mesh and S1
Proto-IH
Rotationflangeis set to 5.7 and 5.6 keV, respectively, corresponding to the input energy of the RFQ. The
Anker connector
dimensions of
to scover the primary surface muons (rms size of 31
Dthe
e velectrodese l o p maree ndesigned
t itemBand
mm and 14 mm in the horizontal and vertical directions, respectively [30]) and to provide a+
Mu (μ e e ) sufficient extraction efficiencyTunerfor ultraPrototype
slow muons.
voltage applied to other(1/3 The
model)
Real electrodes Real IH-DTL
Tuner(S2, S3 and S4)model
is determined using the simulation described below such that the phaseetup @Low-power test
Phys.
Rev.
AB 21,'
Tuning range = 0-50mm(Pickup)~ 1320space of the
beammatchedwiththedesignacceptance
of
the
RFQ
and
a
high
transmission
6
cell
16
cell
050101 (2018)
efficiency is obtained.
~ 320
130 distributions areVNA
450
Input muon
estimated using
a simulation
based
Design:Phys. Rev.
AB on measurements.6
The simulation for a surface muon beamline
H-line)is constructed using the19, (MLF
040101(2016)
g4beamline [15, 31]. The absolute number~ 250 of surface muons is normalized by measurements from another beamline (MLF D-line [32]) that uses the same muon production[mm]
2021/6/28
Muon g-2 theory initiative workshop
17
(
~ 250
Model
fabricated to evaluate
4/28

Model used in E34 experiment[mm]structure (DLS) traveling-wave linac is used when β is greater than 0.7 (42 MeV) [28]. The
details of each acceleration cavity are described below.

Muon linac (3)Tank (11 cells) × 14

16.15 m• DAW-CCL
Table 7

3/7

• Disk-Loaded
DSL
Structure

Output beam parameters of the DAW-CCL.

Outputαx
4.1
Fig. 3 Configuration of the muon linac.
βx [mm/mrad]
0.23
εx [π mm mrad, rms, normalized ] 0.332
DAW parameters
αy-6.9
βy [mm/mrad]
0.36
Frequency [MHz]1296εy [π mm mrad, rms, normalized ] 0.201
Length [m]16.15
αz-0.002βz [deg/MeV]24
In front of the
RFQ, there is an electrostaticcalled[MeV]a Soa lens [29],which accelerates
Inputlensenergy4.26
εz [π MeV deg, rms, normalized ]0.108
Transmission
and extracts 99.80%
the thermal muons.
Output energy [MeV]
41.4
Transient time
106 nsFigure4showsaschematic
view
of
the
Soa
lens.
The
Soa
lens
consistsof two mesh
Survival rate
96.1%
Gradient [MV/m]
5.6
Transmission total
95.9%
electrodes andthree cylindrical electrodes. The first mesh electrode (target mesh) covers the

doublet− The 1stQtank:to ×
be13fabricated(4.5βλ)in FY2021.
2.2.

− Intended to nearly finalize the detailed
design in FY2021.

¾ DLS is widely used as electron LINAC.
‐ E.g., KEK injection S-band DLS
Initial electrostatic
acceleration
co-axial

bridgecoupler# of tanks

14

downstream surface of the silica aerogel target. The laser ionization region is between thebe due to the assembly process of the cavity. Based on the measurement results in the cold
Q-doubletPower
4.5
model, the actual DAW-CCL has been designed
the firstandtankssecond
will be soon
fabricated.
targetandmeshmeshelectrode (S1).
The[MW]
voltage applied to thetarget mesh
and S1
http://www-linac.kek.jp/seminar/2018/linac-beam-kamitani.pdf
DAWtank (11 cells)
is set to 5.7 and 5.6 keV, respectively, corresponding
the DLS
input forenergyof theRFQ. The is matching¾ The key totousemuon
accelerationthebeam
velocity
& the
phase
velocityof micro-wave.
dimensions of the electrodes are designed tocover
the primarysurfacemuons(rms sizeof 31change cell
length to
beand
𝐷 to provide /3
mm and 14 mm in the horizontal and vertical directions,
respectively[30])asufficient extraction efficiency for ultra slow muons. The voltage applied to other electrodes−simulation
Various
R&Ds
are
we needtocalculatetheon-going.
energy(S2, S3 and S4) is determined using the So,
described
below suchthat&thephase increase of each cell.
MV/m𝐷
cos 10 deg
space of the beam matched with the design acceptanceofΔthe RFQ20
anda hightransmission(MCP)-based
BWM,‣ Micro-Channel-Plate
Assumption: acceleration E-field is constantefficiency is obtained.

• Bunch width & beam profile monitors(BWM & BPM)

‣ CsI BPM (for the surface muons),

Input muon distributions are estimated using a simulation based on measurements.
(SOI) pixels
for BPM,‣ Silicon-on-Insulator
The simulation for a surface muon beamline(MLF H-line) is constructedusing theFig. 12
Prototype of the DAW-CCL:(Left) mechanicaldrawing,
g4beamline[15,three-dimensional31]. The absolute
number of
surface muons
is normalized by measureBPM.
‣ Strip-line(Right) assembly of the prototype.
ments from another beamline (MLF D-line [32]) that uses the same muon production
2021/6/28
Muon g-2 theory initiative workshop
2.6. DLS

4/28

18

Injection (1)• Need to develop the 3D spiral injection scheme
for the small muon orbit.
− 66 cm diameter orbit under the magnetic field of 3 T.
− Extensive simulations to optimize the injection parameters
66 cm
and kicker spec., reflecting the magnet design updates.

3D spiral
injection

Updated iron yoke

H-line in MLF at J-PARC

Injection Shimmingtunnel holes (coarse)
Shimming
holes (fine)Lq. Heservice hole2021/6/28

Muon g-2 theory initiative workshop

19Demonstration of the 3-D spiral injection using the electron beam

Injection (2)We will demonstrate the 3-D spiral injection scheme on
We will demonstrate the 3-D spiral injection scheme on
the test bench, which is a scaled-down version of
the test bench, which is a scaled-down version of
the production experiment.
the production experiment.
In the future,
In the future,
we will install the pulse magnetic field kicker device.
⼤きなズレはない
we will install the pulse magnetic field kicker device.
⼤きなズレはないPrototype pulse magnetic field• In parallel, a demonstration experiment of the spiralinjection using electrons is progressing well.

Confirm
the trajectory
deviationofpulsedbeam
kicker devicefor ourtest benchrajectory
deviationof pulsed
beamtheConfirm
trajectory deviation of pulse− Started to use pulsed beams and Prototype
to devicedesignpulse
field kicker.
kickerformagnetic
our testthebench

K. Oda (Ibaraki Univ.),
Matsushita(Univ.
of Tokyo).
lR.(pulse
InjectDC:100beam
pulsedbeamconditions.
(pulse width :100 μs) under the same conditions.
lsed beam
widthμs) andunder
the same

Wire scan in vertical direction

Schematic
Schematicdiagram
diagramofofthe
theelectron
electrongun
guntesttest bench
bench at
at KEK
KEK

Rep. freq.：1 kHz
Pulsed beam
DC beam
Pulse width：100 μs

DC beamWire scan Wire scan

Wire scan
DC beam
100μs Pulsed
beam 102021/6/28

Exposure time : 20 s

Vertical [mm]DC beam
100μs Pulsed
beam 10

Intensity [a.u.]

Wire scan in vertical direction

Intensity [a.u.]

Intensity [a.u.]l Inject DC beam and pulsed beam(pulse width :100 μs) under the same condl Takepicture magnetof spiralby
trajectoryin the storage magnet by CCD camera.
trajectoryin theastorage
CCD camera.
l Take a picture of spiral trajectory in the storage magnet by CCD camerl Checkthe scan.
vertical beam distribution by wire scan.
m distribution
by wirel Check the vertical beam distribution by wire scan.
l ofWe
confirm
injection
trajectories
ofbeam
the DC
beam and 100μs pulsed beam donʼtajectories
theDC beamand 100μs
pulseddonʼtl We confirm injection trajectories of the DC beam and 100μs pulsed bediffer much.
differ much.
Wire scan in vertical direction

Pulsed beamRep. freq.：1 kHz
Pulse width：100 μs

Wire scan

Pulsed beam
Wire scan

DC beam
100μs Pulsed
beam 10

Muon g-2 theory initiative workshop
time
ExposureExposure
time : 100s : 20 s
Exposure time : 100 s
Vertical [mm]Vertical [mm]2220Exposuretim

Storage magnet (1)66 cm

H-line in MLF at J-PARC

2021/6/28

Muon g-2 theory initiative workshop

MRI-typestorage magnet(3 T, φ66-cm orbit)

21

Storage magnet (2)• Shimming studies for the fine control of magnetic field.

0<NNDQ@ 3CDHHDIB− In collaboration with the Mu hyperfine spectroscopy (MuSEUM).
− The procedure works
well at 1.2 T (< 0.2 ppm, peak-to-peak).
3PK@M>JI?P>ODIB-<BI@O&JM CDBCGT PIDAJMH H<BI@OD> AD@G?
◦ ! NPK@M>JI?P>ODIB NJG@IJD? AJM <KM@>DN@ >JIOMJGG@? H<BI@OD> AD@G?
JA  4

)MJI NCDH KG<O@N KKH KK

Longitudinal position (m)B (T)− Furtherbe carriedout towards 3 T.
! F@T
@G@H@IO tests
AJM OC@will
CDBCAD@G?
@SK@MDH@IO.D>F@G ADGHN KKH KK◦ ! N@>JI?C<I? -2) H<BI@O RDOC
<I <SD<G G@IBOC JA  H <I? <=JM@ ?D<H@O@M JA  HH

◦ 2@LPDM@H@ION AJM OC@ AD@G? <M@◦  KKH NO<=DGDOT ?PMDIB
H@<NPM@H@IO

magnet: 1.2 T• K.Superconducting
Sasaki, M. Abe (KEK).
Axial length: 2 m,
Bore diameter: 925 mm.
2021/6/28◦  KKH K@<FOJK@<F
PIDAJMHDOT DI < NKC@MJD?<G
QJGPH@ RDOC U >H M >H

20

Azimuth (deg.)
Muon g-2 theory initiative workshop-<BI@OD> KPOOT KKH KK+ 3<N<FD - !=@ +%+ - 3PBDO< # /JB<I@ ( )DIPH< )=<M<FD 5

Slidefrom S. Kanda (KEK)21

22

Storage magnet (3).-2 0MJ=@N• Development of the field monitoring systems

4CM@@ OTK@N JA H<BI@OJH@O@M− In collaboration with the Mu hyperfine spectroscopy (MuSEUM).
◦ &D@G? ><H@M<◦ ! >C<II@G MJO<ODIB .-2 KMJ=@ OC<O H<KN
H<BI@OD> AD@G?N DI OCM@@ ?DH@INDJIN
◦ 3OP?D@N <M@ PI?@MR<T AJM NDHPGO<I@JPN HPGOD
>C<II@G M@<?JPON◦ + 3<N<FD +%+  ! 8<H<BP>CD +%+*!32) 4 4<I<F< + 3CDHDUP 5 4JFTJ  ( 4<?< .<BJT< 5◦ &DS@? KMJ=@◦ ! >JHK<>O KMJ=@ OJ HJIDOJM H<BI@OD> AD@G?
NO<=DGDOT ?PMDIB @SK@MDH@IO
◦ 3O<I?<M? KMJ=@◦ ! CDBCKM@>DNDJI .-2 KMJ=@ OJ ><GD=M<O@ JOC@MN
◦ !I <>>PM<>T JA  KK= C<N =@@I <>CD@Q@?
◦ #MJNN><GD=M<ODJI DN PI?@MR<T DI < EJDIO M@N@<M>CKMJE@>O =@OR@@I *<K<I <I? OC@ 53
◦ + 3<N<FD +%+  ! 8<H<BP>CD +%+*!32)  4 4<I<F< 3 3@J 5 4JFTJ 
0 6DIO@M !.,  $ +<R<GG 5 -<NN  $ &G<T 5-<NN*,<=

2021/6/28

Muon g-2 theory initiative workshop
23

Slide from S. Kanda (KEK)23

Positron tracking detector (1)2021/6/28

Muon g-2 theory initiative workshop

24Positron tracking detector (2)• Major components are in or completed the mass productions.
• Extensive studies and tests are on-going for the detector assembly.

2021/6/28

Muon g-2 theory initiative workshop

25

Expected sensitivities
1

1.3x10-5.
• ~2-year running will reachthe BNL precision of aμ
assuming

0.75

0.5

0.25

− 2.2x107 s data taking time,
Recon.

Det. acc.

E(e+) win.

KickerInjectionDLS

DAW-CCL

IH-DTLRFQ

Soa lens

Mesh elec.

Thermal μ+

Thermal Mu

0Transport

x10
Surface μ+

Muon efficiency [a.u.]• Overall μ+ efficiency ofTransmision only
Transmission + decay loss

Simulation− 1 MW proton beam,➢ 5.7x1011 e+ʼs for analysis,− 50% μ+-polarization.

Expected uncertainties
Stat.

Syst.

δaμ
[ppb]

450

< 70

δEDM
[10-21 e・cm]

1.5

0.36

Systematic
uncertainties will
be much smaller than the statistical ones.
2021/6/28
Muon g-2 theory initiative workshop
26

Schedule
2020 and
2021 milestone
2022
2023
2024
2025
2026 31
Intended schedule and milestones
Surface
KEK
muon
BudgetBldg. andSurfacefacilitymuon
Muon
Bldg. andsourcefacility
LINAC

Muon
sourceInjection and
LINAC
storage

Storage
Injection andmagnetstorage
Detector
Storagemagnet
DAQ andDetector
computingAnalysis
DAQ andcomputing

2020

2021

2022

2023

2024

First
result

2025

2026

Now
★ Beam at H1 area

★ Beam at H2 area

★ Final design★ Beam at H1 area

★ Beam at H2 area

★ Ionization@S2★ Finaltest
design★ Completion★ Ionization test at★H2Completion

Commissioning
Commissioning

KEK
FY
BudgetDatataking★ 1 MeV acceleration@S2★ 210 MeV
★ 4.5 MeV@ H2★ Ionization test
★ Ionization test @S2★at10H2MeV

Data taking
Data taking First

result?

★
MeV acceleration@S2★1Completionof★ 210 MeV
★ muon injection★ 4.5 MeV@ H2
electron injection test
★ 10 MeV★ Install★ B-field probe★ Completion of★ Shimming
done
ready
★ muoninjection
electron injection test
★ Mass production ready★
★Installation
Install★ B-field probe★ Shimming doneready
★ Mass production ready★ Ready ★ Installation★ Analysis software ready★ Ready★ Analysis
environment ready

31

• The
experiment was endorsed as the near-termby KEK Science
Analysis★ Analysis softwarepriority
ready31
Advisory Committee (SAC) (2019.3). ★ Analysis environment ready• KEK prepares for the funding request to MEXT (2020.6-).
2021/6/28

Muon g-2 theory initiative workshop

27Collaboration
at Seoul National University, June 24-27, 2019

• Now 116 members from Canada , China, Czech, France,
Japan, Korea, Russia and USA, and still growing.
•2021/6/28
New collaborators arehighly welcome.
Muon g-2 theory initiative workshop
28Summary• J-PARC E34 intends to measure the muon g-2 andEDM with a new experimental approach.
− Very different experimental approach from that of the BNL/FNAL experiments.
✓ Small-emittance muon beam with no strong focusing,✓ MRI-type storage ring with a good injection efficiency andhigh uniformity of local B-field,✓ Full-tracking detector with large acceptance.

• The experiment is getting ready for realization.
− The development and construction is in progress to start datataking in FY2025.
✓ R&Ds of the experimental apparatus keep progressing well,✓ Funding requests are being made to MEXT,✓ Intending to reach the BNL precision in ~2-year running.
2021/6/28

Muon g-2 theory initiative workshop

29