COMET
mu-e conversion search experiment at J-PARC

Satoshi MIHARA
KEK/J-PARC/Sokendai

Outline•

Introduction•••

Muon particle physics & mu-e conversion

COMET experiment at J-PARC•

Status of the experiment•

Plan of the experimentSummary

COMET Cyclotron
at PSI

Muon particle physics&mu-e conversion

Muon Particle Physics
Muon in the Standard
Modelct

Hup

charm

top

104MeVdsb

downstrangebottom0.511KeV

105.7MeV

1.777GeVeμτelectron

muontau< 0.17MeV< 15.5MeV< 2.2eVνe νμ ντggluon

γphoton
80.4GeV

91.2GeVWZW boson

Z bosontio
ratiodge

neera2ndgenra
enemuon g-2, B leptonic
decay …

τ neutrino

Higgsnμ neutrino

3re neutrinotg•

4.2GeVstrong interaction
electro-magnetic interaction
weak interaction

utionIndication of BSM related
to muon?

125-6GeV

4.8MeV

1s•

Establishment of SM

171.2GeVn•

Precise measurement ofmuon properties

Boson

1.27GeV

2.4MeV

quark•

Fermionlepton•particles composing materialparticles
mediatingforcesparticlegenerating
massBranching Ratio ULqγqγ, ZʼμBernstein & Coopereμeeγ, ZʼeμeYearmμL= 2H dipole + 2 κJ eνμ J ν , ee
Λ (1+κ)Λ (1+κ)mu-e Conversion

Phase I
Phase I−µκ=0
MEG 2016
4.2x10-13

Muon Decay In Orbit

Andre Schöning, Mu3e Collaboration−12−µà e νν
nuclear muon captureµ − + ( A, Z ) à ν µ + ( A, Z − 1)

μ-e conversion−µ + (A, Z) à e− + ( A, Z )Andre de Gouvea, W. Molzon, Project-X WS(2008)

PSI, OpenExperimental Techniques
SINDRUM II•--

Process : μ +(A,Z) →e +(A,Z)• A single mono-energetic electronµ−• Eμe ~ mμ-Bμ :105 MeV for AlMuon Decay In Orbit• Delayed：~1μS

nuclear muon capture• No accidental backgrounds• Physics backgrounds• Muon Decay in Orbit (DIO)-14• Ee > 102.5 MeV (BR:10)-16• Ee > 103.5 MeV (BR:10)• Beam Pion Capture-• π +(A,Z) → (A,Z-1)* → γ+(A,Z-1)+ γ→e eRext=

number of proton between pulses
number of proton in a pulse

capture in the moderator (see also Fig.3.1 andthe discussion in the text).

Electron Energy

events / 100 keV

run2000 on gold

103

102

10

SINDRUM IImeasurementµe2ν simulation-11µe simulation at B=10

DIO electrons
Signal1
70

80

ETOT (MeV)

90100emt
aiat
FfoT!

Nw

Selection of the Target Material•••

DIO Eendpoing extends to the Eμ-e•Recoil energy•Muon binding energy

Select the target material with high Eμ-e andavoid using the material with larger Eendpointaround the target•

When the target is made of aluminium,
we should avoid using materials from
Z=5 to Z=12.

•He (Z=2) is OK to use around the target

Lifetime of muon in muonic atoms•

Shorter in larger Z because of the larger
nuclear muon capture rate

HeAlTiOnce the signal is observed…
Even without μ->eγ signal !
CIRIGLIANO, KITANO, OKADA, AND TUZONPHYSICAL REVIEW D 80, 013002 (2009)

μVector 2eVector 1
DipoleScalar
Al TiPbμ-e Conversion SearchExperiments••J-PARC
•

DeeMe

•

COMET Phase-I & IIFNAL

パイ中間子生成標的
パイ中間子捕獲磁石•Mu2e (A. GAPONENKOʼspresentation)

陽子ビーム

ミューオン
輸送磁石

ミューオン
静止標的

電子輸送磁石電子
パイ中間子 → ミューオン

10-14 ~ 10-16 sensitivity

電子検出器

COMET Phase-II- 検出器ソレノイド磁石- ストローチューブ飛跡検出器- LYSOカロリメーター

J-PARC
Japan Proton acceleration research complex•

Joint project between JAEA and KEK•

New and accelerator research facility, using
MW-class high power proton beams at both 3
GeV and 30 GeV.
Various secondary particle beams••••

neutrons, muons, kaons, neutrinos, etc.
produced in proton-nucleus reactions

Three major scientiﬁc goals using thesesecondary beams•

Particle and Nuclear physics•Materials and life sciences•

R&D for nuclear transformation (in Phase 2)

The anticipated goal is 1 MW

J-PARC TokaiKEK Tsukuba

LINAC

400 MeV

Neutrino beam to Kamioka

Rapid Cycle Synchrotron
Material and Life
Science Facility

Nuclear and Particle
Physics Exp. Hall

Energy : 3 GeV
Repetition : 25 Hz
Design Power : 1 MW

Main Ring

Max Energy : 30 GeV
Design Power for FX : 0.75 MW
Expected Power for SX : > 0.1 MWCOMETCOMET at J-PARC•

Target S.E.S. 2.6 10-17• Pulsed proton beam at J-PARC• Insert empty buckets for necessary
pulse-pulse width• bunched-slow extraction• pion production target in a solenoid magnet• Muon transport & electron momentum
analysis using C-shape solenoids• smaller detector hit rate
• need compensating vertical ﬁeld
• Tracker and calorimeter to measureelectrons• Recently staging plan showed up. The
collaboration is making an eﬀort to startphysics DAQ as early as possible under this.

Transport Solenoid

COMET Phase I & II•75

5.3. MUON TRANSPORT

Phase I

Pion production target

Radiation shieldProton beam

Capture solenoid
Matching solenoid•

Beam background study

Phase ICOMET Solenoids and Detectors
for the CDR
version 090609.001

Muon beam transport solenoid

Late-arriving particle tagger•

Phase II

Achieve an intermediate
Beam collimatorsensitivity of < 10

Muon stopping target

Beam blocker-14

DIO blocker

Muon target solenoid•8GeV, 3.2kW, 110 days of DAQ

Calorimeter

TrackerCurved sepctrometer solenoid
Detector solenoid•Phase II

Phase I
Figure 5.14: Present design of the solenoid channel used in the tracking studies.
5.3.2.2 Dipole fields for drift compensation2013-2018
To keep the center of the helical trajectories of the muons with reference momentum p in
the bending plane, a compensating vertical dipole field should be applied. The magnitude
Facility constructionof the compensating dipole field is given by!
"1 p1
2013-2019
B=cos θ +,
(5.6)
qR 2
cos θ
Magnet construction & installation
2018-2020Eng. run & Physics run
Phase IIEng. run in 2022(?)
0•

8GeV, 56kW, 1 year DAQ toachieve the COMET ﬁnal goal
-16of < 10sensitivity

comp000

Pion Capture•

Adiabatic transition of Muon beam•

As B decreases, pT decreases and RincreasesBl•

more parallel beam at a cost of theincreased beam size

Strong Magnetic ﬁeld in highradiation environment

Aluminum stabilized SC
Collaborative R&D between
COMET & Mu2e

Muon Transport•

A center of helical trajectory ofcharged particles in a curved
solenoidal ﬁeld is drifted by••This eﬀect can be used forcharge and momentum
selection.

This drift can be compensatedby an auxiliary ﬁeld parallel tothe drift direction

δp/δx = 1 MeV/c/cm

COMET Phase-I

Status of COMET Experiment Facility
Switch Yard Beamline Elements

A-LineB-LineBeam line component
installation in progress inSY since 2014

Beam transport line in HD hall

SC magnets

Hall construction

He compressor used
for E36 will be reused
for COMET

Significant construction work 2016
Summer to connect SY and Hall
along the B-Line

90 deg. Transport
Solenoid installed inSpring 2015

COMET Hall ready in Spring 2015

COMET:Status of Detector Preparation
All geometry implemented
in the full simulation:
ICEDUST

Detector for physics
measurement in Phase IAnalysis algorithm development inprogress using simulation data.
ex) track finding in CyDET

Beam test @ PSI 2015

Trigger Hodoscope Counter
Scintillator + Cerenkov

CDC : the main detector ofCOMET Phase-I Physics

Wire stringing
completed in July
2016 at KEK
CDC Read Out
Electronics RECBE
production atIHEPCDC Construction•

COMET Phase-I Physics
Main Detector•

Wire stringing completedin July 2016•

1st cosmic-ray event
observed in Sep. 2016

COMET: Detector Preparation ContʼdStraw tracker (operational invacuum) prototype

Detector for beam BG measurement
in Phase I and physics measurement
in Phase II

Ecal Pile-up study using
simulation data

ECal (LYSO) R&D using
prototypes

Crystal quality test bench at JINR

100 MeV electron↑Wave form taken in the testß Electron beam test at ELPH

Ecal PID performance evaluation at PSI 2015

Backgrond Assessment•

Proton emission from muon captures•

No data available for Al•

S. Sobottka and E. L. Wills.
Phys. Rev. Lett. 20 (1968) 596

Si data only (near Al)•

15% proton emission / muon
28
capture on Si•

50MeV/c < p < 200MeV/c•

Signiﬁcant contribution to the detector
hit rate•

AlCap experiment at PSI•Si

Joint eﬀort between COMET/Mu2eAl

0.05 protons/ muon capture• Tran Hoai Nam (Osaka Univ.) PhD•

opportunities for cooperation with Mu2e
M

C

AlCap@PSI

CC

Dec. 13

MM

CM

C

M

C
M

CC
M

COMET
Mu2e

Background Phase-I

Preparation for Phase-II•

180 degree bend in the muontransport section•Better pi/mu separation andhigh-p particle rejection•

180 degree bend in the electronspectrometer•

Keep the detector
occupancy rate reasonableeven with higher primarybeam power•

Optimization of•muon stopping targetdisks•

collimators in theelectron spectrometer•

Detector R&D as a beammeasurement detector in Phase-I

Phase-I

Phase-IIPrinciple of DeeMe→ DeeMePrinciple of DeeMe→ DeeMeDeeMe at J-PARC
mu-e conversion search at JPARC with a S.E.S. of 10-14• Primary proton beam from RCS• 3GeV, 1MW• Pion production target as a muon stopping
target•Beam line as a spectrometer• Kicker magnets to remove prompt
background• Multi-purpose beam line for DeeMe, HFS,
g-2/EDM is under construction• Engineering run (DIO electronmeasurement) in JFY 2016

Acceptance (sr/MeV/c)•0.25

From a Target ÷ 40
H-port Frange
GV Entrance
GV ExitHS2 Entrance
HS3 Entrance
HSEP Entrance
HB4 Entrance
HB4 Exit
HQ2 Entrance
Focus

0.2

0.15

0.1

0.05

070

80

90

100

110

120130Momentum (MeV/c)

Summary•muon as a tool to investigate BSM
physics•COMET searches for the mu-econversion with a target sensitivity-16
better than 10 at J-PARC••-14

Staged approach: < 10-16
and <10 in Phase II

in Phase I

Facility construction & detector
preparation are in progress to start
Phase-I in 2018-2019

Summary•muon as a tool to investigate BSM
physics•

COMET searches for the mu-econversion with a target sensitivity-16
better than 10 at J-PARC
presented at PSI2013
•

•

-14

Staged approach: < 10-16
and <10 in Phase II

in Phase I

Facility construction & detector
preparation are in progress to start
Phase-I in 2018-2019
Bld. construction completedin 2015 spring