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1 J-PARC J-PARC

2 J-PARC

3 (clfv)

4 CKM (mν=0) ν MNS clfv µ + e + γ Lµ : -1 0 Le : 0-1 (clfv) µ + e + e - e + Lµ : Le :

5 clfv clfv mixing W e e O(10-50 ) clfv clfv

6 clfv

7 Various Model Predict Charged Lepton Mixing

8 Charged Lepton Mixing by SUSY µ + e + γ m 2 l = ( m 2 11m 2 12m 2 13 m 2 21m 2 22m 2 23 m 2 31m 2 32m 2 33 ) In SUSY, clfv processes are induced by the off-diagonal terms in the slepton mass matrix. In MSSM, no offdiagonal terms and need other mechanisms. SUSY-GUT SUSY-Seesaw

9 How are Sleptons M_planck SUSY-GUT GUT Yukawa interaction SUSY Seesaw Model Neutrino Yukawa interaction (m 2 L) 21 3m2 0 + A 2 0 8π 2 h 2 t V td V ts ln M GUT M Rs (m 2 L) 21 3m2 0 + A 2 0 8π 2 h 2 τ U 31 U 32 M GUT M Rs CKM matrix Neutrino oscillation

10 SUSY Predictions SUSY-GUT(SU5) PRISM-Phase 1 PRISM-Phase 2

12 µ! + (A, Z) " e! + (A, Z) 1s!"#$%"& µ!!"#$%&'()"*!(#&+,"'%!"#$%&'()*%+$%#,-+. µ! " e! ## µ! + (A, Z) " # µ + (A, Z!1)!Le =1!L" =1 Signal (m"-b") Background muon decay in orbit radiative pion/muon capture muon decay in flight, cosmic rays! 105MeV 3

13 events / channel SINDRUM-II PSI events / channel 10 SINDRUM II Class 1 events: prompt forward removed MIO simulation e - measurement µe simulation e + measurement MIO simulation µe simulation Class 2 events: prompt forward momentum PSI Class 1 events: prompt forward removed e - measurement e + measurement Class 2 events: prompt forward momentum (MeV/c) A exit beam solenoid B gold target C vacuum wall D scintillator hodoscope E Cerenkov hodoscope A H SINDRUM II F G H I J inner drift chamber outer drift chamber superconducting coil helium bath magnet yoke B(µ + T i e + T i) < decayed veto veto D Final result on mu - e conversion on Gold target is being prepared for publication < 7 x %CL I C B H D G J F E 1m configuration 2000

15 BNL/AGS MECO (the US) To eliminate beam related background, beam pulsing was adopted (with delayed measurement). To increase a number of muons available, pion capture with a high solenoidal field was adopted. For momentum selection, curved solenoid was adopted.!"#$%&'($#)*#+,-#./ The MECO Experiment 09*#+38.<93/,.:!+1.6*8+/$087#.8,< >C@?$!$B$C@F$!D 09*#+38.<93/,.: =+8<93/,8.$087#.8,< >?@A$!$B$C@?$!D %98.$0/8**,.:!1+:#/ at BNL 0/+12$!+134#+ '877,-1/8+6 09*#+38.<93/,.: E#/#3/8+$087#.8,< >C@A$!$B$F@A$!D Aim for '+56/17 '178+,-#/#+ %98.$;#1-0/8* Construction funding ~2005 Start physics run ~2010 Cancelled in 2005 CANCELLED

16 J-PARC µ-e New Experiment PRISM Production Target Stopping Target B(µ + Al e + Al) < J-PARC PRISM-Phase1 B(µ + T i e + T i) < PRISM-Phase2

17 Brookhaven MECO 2005 Fermilab mu2e MECO :EoI, 2007 EOI :LoI!"#$%&'($#)*#+,-#./ The mu2e Experiment 0/+12$!+134#+ 22 batches = s MI cycle %98.$0/8**,.:!1+:#/ NEUTRINO PROGRAM MUONS Booster Batches 4.6!10 12 p/batch 09*#+38.<93/,.:!+1.6*8+/$087#.8,< >C@?$!$B$C@F$!D 09*#+38.<93/,.: =+8<93/,8.$087#.8,< >?@A$!$B$C@?$!D '877,-1/8+6 09*#+38.<93/,.: E#/#3/8+$087#.8,< >C@A$!$B$F@A$!D Aim for '+56/17 '178+,-#/#+ %98.$;#1-0/8* Construction funding ~2005 Start physics run ~2010 B(µ + Al e + Al) < CANCELLED Accumulator (NuMI +Muons) Recycler 56!10 12 p/sec (NuMI) Debuncher (Muons) 4!4.6!10 12 p/1467ms = 12.5!10 12 p/sec (Alternative: 24 batches=1.6s MI cycle" 11.5!10 12 p/s) 0.1s 1.367s

18 1 (BR~10-16 ) PRISM-Phase1 COMET (COherent Muon Electron Transition) Production Target Stopping Target B(µ + Al e + Al) < 10 16

19 COMET Production Target Stopping Target muon/sec

20 10 11 / Extinction=( )/( ) 10-9!sec P!~40MeV/c P!<75MeV/c curved solenoid <2x m

21 Pulsed Proton Beam (1) " & +#A,Z% " #A,Z&1%* "!+#A,Z&1%! " e + e & # & +#A,Z% " e & +#A,Z% : #$1#s% Extinction N bg = N P!Y "/P!A "!R ext!p!!a N P : total # of protons #$10 21 % Y "/P : " yield per proton #0.015% A " : " acceptance #1.5!10 &6 % R ext : Extinction Ratio #10 &9 % P! : Probability of! from " #3.5!10 &5 % A : detector acceptance #0.18% N bg < 0.22 Extinction < 10 &9 Extinction: < 10 &9 Power: 60 kw #4!10 13 pps@8 GeV%

22 Pulsed Proton Beam (2) : Bunching Scheme J!PARC Accelerator Complex RCS : 1 bunch operation h=1 or h=2 w/ empty bucket MR : Empty bucket Scheme h=9 or h=8 Adiabatic dumping : small 30 GeV! 8 GeV Reduce RCS painting area Smaller 3!50BT collimator 8 GeV, 7 "A ; 56 kw to NP!Hall MECO!like Scheme

Pion Capture A large muon yield can be achieved by large solid angle pion capture by a high solenoid field, which is produced by solenoid magnets surrounding the proton target. P T (GeV/c) = 0.

23 Pion Capture A large muon yield can be achieved by large solid angle pion capture by a high solenoid field, which is produced by solenoid magnets surrounding the proton target. P T (GeV/c) = 0.3 B(T ) ( R(m) ) 2 B=5T,R=0.2m, PT=150MeV/c. Superconducting Solenoid Magnet for pion capture 15 cm radius bore a 5 tesla solenoidal field 30 cm thick tungsten radiation shield heat load from radiation a large stored energy 1400 target Proton beam 3600

24 Muon Transport Beamline Muons are transported from the capture section to the detector by the muon transport beamline. Requirements : long enough for pions to decay to muons (> 20 meters 2x10-3 ). high transport efficiency (Pμ~40 MeV/c) negative charge selection low momentum selection (Pμ<75 MeV/c) Straight + curved solenoid transport system is adopted.

25 Charged Particle Trajectory in Curved Solenoids A center of helical trajectory of charged particles in a curved solenoidal field is drifted by D = p qb θ bend 1 2 ( cos θ + 1 cos θ D : drift distance B : Solenoid field! bend : Bending angle of the solenoid channel p : Momentum of the particle q : Charge of the particle! : atan(p T /P L ) This effect can be used for charge and momentum selection. ) This drift can be compensated by an auxiliary field parallel to the drift direction given by B comp = p qr 1 2 ( cos θ + 1 cos θ p : Momentum of the particle q : Charge of the particle r : Major radius of the solenoid! : atan(pt/pl) ) Tilt angle=1.43 deg.

26 Design of Muon Transport Beamline (preliminary) Solenoid field Compensation field Inner radius

27 Spectra at the End of the Muon Transport Preliminary beamline design main magnetic field compensation field radius of magnets (175 mm) Spectra at the end of the beamline (top left) total momentum (top right) direction angles to beam axis (bottom left) time of flight (bottom right) beam profile muons for open histograms, pions for hatched histograms. 75 MeV/c Transport Efficiency # of muons /proton # of stopped muons /proton # of muons of pµ >75 MeV/c /proton x10-4

28 Overview of the New Experiment : COMET Production Target The beamline design is very important to reduce the beam intrinsic B.G. Stopping Target ID signals B.G. reduction hit rate reduction

29 COMET

to eliminate low-energy beam particles and to transport only ~100 MeV electrons.

30 to detect and identify 100 MeV electrons. under a solenoid magnetic field. to stop muons in the muon stopping target. to eliminate low-energy beam particles and to transport only ~100 MeV electrons. Detector Components a muon stopping target, curved solenoid,tracking chambers, and a calorimeter/trigger and cosmic-ray shields.

31 Detector and Spectrometer To identify the genuine mu-e conv. enevts from a huge number of B.G. events. signal : a 105MeV electron from the stopping targets. background : muon decay in orbit etc. Muon Decay in Orbit (DIO) Main B.G. source Electron spectrum from muon decay in orbit energy timing as precisely as possible Reject using a curved solenoid spectrometer Energy spectrum of electrons from decays in orbit in a muonic atom of aluminum, as a function of electron energy. The vertical axis shows the effective branching ratio of μ-e conversion. DIO/MUC (E end E e ) 5 Signal Ee (MeV/c)

32 Mom. Selection in a Curved Solenoid D = p qb θ 1 bend 2 ( cos θ + 1 ) cos θ Collimator Detector solenoid 30MeV/c 60MeV/c 105MeV/c Curved solenoid spectrometer Traget solenoid Top view Side view 32

33 Transmission of the Electron Transport (CS) Electron Transport System Parameters (preliminary) Radius : 50 cm Magnetic field : 1 Tesla Bending angle : 180 degrees Geometrical Acceptance Solid angel at the target : 0.73 mirror effect at a graded field Transport efficiency : 0.44 Total : 0.32 Suppression of electrons from decay in orbit. about 10-8 suppression about 1000 tracks / sec for stopping muons. DIO/Stopping-µ Ratio of a number of electrons reaching the end of transport to all electrons emitted in 4π. Acceptance DIO survival rate Eth (MeV) Momentum (MeV/c) (a) 2T-1T 3T-1T 4T-1T R(cm)

Electron Detection (preliminary) Under a solenoidal magnetic field of 1 Tesla. In vacuum to reduce multiple scattering. Straw-tube Trackers to measure electron momentum.

34 Electron Detection (preliminary) Under a solenoidal magnetic field of 1 Tesla. In vacuum to reduce multiple scattering. Straw-tube Trackers to measure electron momentum. should work in vacuum and under a magnetic field. A straw tube has 25μm thick, 5 mm diameter. One plane has 2 views (x and y) with 2 layers per view. Five planes are placed with 48 cm distance. 250μm position resolution. Electron calorimeter to measure electron energy and make triggers. Candidate are GSO or PbWO2. APD readout (no PMT).

35 Momentum Resolution 5 stations in vacuum One station has two views (x and y). One view has two layers. Straw tube has 25μm thickness. Position resolution : 250 μm 230 kev/c in sigma (multiple scattering dominated.) Residual distribution between reconstructed and true momenta / 7 Constant Mean E E-02 Sigma E !P (MeV/c)

36 Cosmic Ray Shields Both passive and active shields are used. Passive shields 2 meter of concrete and 0.5 m of steel Active shields layers of scintillator veto counters (~1% inefficiency)!"#$%&'&!.+/$'0-&+(10&)2 ('%03+($0#'0))4'"% ('&&) *)""%+,&-&)!5%-&2+(")&#"02+(3&$'%"6&'&%

Signal Acceptance 800 700 600 ID Entries Mean RMS 202 3820 104.1 0.

400 300 200 100 Signal region 0 98 100 102 104 106 108 rec Pe (MeV/c) Items geometrical solid angle at target transport

37 Signal Acceptance ID Entries Mean RMS The signal acceptance is given by the geometrical acceptance of the detector and the analysis (cut) acceptance Signal region rec Pe (MeV/c) Items geometrical solid angle at target transport efficiency analysis energy cut pt > 52 MeV/c cut time window cut Acceptance total 0.07 signal energy window ( MeV in uncorrected energy scale)

38 single event sen. B(µ + Al e + Al) N! 6x10 17 muons. fcap 0.6 Ae acceptance 0.07 B(µ + Al e + Al) = 1 N µ f cap A e, 8GeV / = x x10 17 B(µ + Al e + Al) < (90% C.L.)

39 Background (1) Backgrounds Events Comments Muon decay in orbit Radiative muon capture Muon capture with neutron emission Muon capture with charged particle emission 0.05 <0.001 <0.001 < kev resolution (2) Radiative pion capture* Radiative pion capture Muon decay in flight* Pion decay in flight* Beam electrons* Neutron induced* Antiproton induced <0.02 < prompt late arriving pions for high energy neutrons for 8 GeV protons (3) Cosmic-ray induced Pattern recognition errors 0.04 < veto efficiency Total 0.34

40 COMET DRAFT J-PARC NP-Hall

41 ( ) J-PARC B(µ - +Al e - +Al)<10-16 Background J-PARC PRISM-Phase1 LoI J-PARC COMET

Μ粒子電子転換事象探索実験による世界最高感度での荷電LFV探索第3回機構シンポジューム 2009年5月11日素粒子原子核研究所　三原　智

Μ粒子電子転換事象探索実験による世界最高感度での荷電LFV探索第3回機構シンポジューム 2009年5月11日素粒子原子核研究所　三原　智 µ COMET LFV esys clfv (Charged Lepton Flavor Violation) J-PARC µ COMET ( ) ( ) ( ) ( ) B ( ) B ( ) B ( ) B ( ) B ( ) B ( ) B 2016 J- PARC µ KEK 3 3 3 3 3 3 3 3 3 3 3 clfv clfv clfv clfv clfv clfv clfv