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COMET at J-PARC: Proton-Muon Beam Experiment

An introduction to the COMET experiment at J-PARC, the Japan Proton Acceleration Research Complex. The seminar covers the J-PARC facility, its goals, beam power curves, damage caused by earthquakes, and mu-e conversion physics.

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COMET at J-PARC: Proton-Muon Beam Experiment

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  1. mu-e conversion search experimentCOMET at J-PARC • Satoshi MIHARA • Satoshi.mihara@kek.jp • KEK, Japan 17/May/2011 Pisa Seminar 2011

  2. Outline • J-PARC Introduction • COMET at J-PARC • Proton/Muon beam at J-PARC • Detector • Sensitivity and Background • (R&D Status) • Schedule and Cost • Summary 17/May/2011 Pisa Seminar 2011

  3. 11/Mar Quake Afterquakes Previous quakes Eurasia Plate North American Plate Pacific Plate Philippine Plate Tohoku Earthquakes and Tsunami • Japan has been deformed by the earthquakes of Mar 2011 • The earth itself too • daily rotation speed changed and day length has been shortened by 1.8μsec • Tsunami was induced by the quakes. • Afterquakes continue 17/May/2011 Pisa Seminar 2011

  4. J-PARC Introduction • What is J-PARC (Japan Proton Acceleration Research Complex)? • Joint project between JAEA and KEK • New and exciting 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 these secondary beams • Particle and Nuclear physics • Materials and life sciences • R&D for nuclear transformation (in Phase 2) • The anticipated goal is 1 MW 17/May/2011 Pisa Seminar 2011

  5. J-PARC Accelerator 3GeV proton Muon Neutron < 30GeV proton Muon Kaon 17/May/2011 Pisa Seminar 2011

  6. An Expected Beam Power Curvesdefined before the earthquake PMR(8-bunch@30GeV) = 1.6xPRCS /MR CYCLE ( ): Beam transfer ratio from RSC to MR RCS POWER FOR MR ★ 0.72MW Linac energy upgrade 6sec (2.7%) now MR CYCLE [sec] BEAM POWER [MW] 3.52sec (4.5%) 3.2sec (5.0%) MR POWER AT 30GeV 2.47 (6.5%) 2.23sec (7.2%) (maximum cycle with existing power supply) 1.0sec (16%) 2008 2009 2010 2011 2012 2013 2014 2015 H20 H21 H22 H23 H24 H25 H26 H27 JFY 17/May/2011 Pisa Seminar 2011

  7. J-PARC Damage by Earthquakes • No damage by Tsunami • All equipments are standing at where they should be but... • Need alignment again • LINAC/T2K near detector floors were covered by underground water • quickly removed when the electricity was recovered • Many cracks on the wall in tunnels • Vacuum inspection is necessary • Inspection and recovery are in progress • Plan to provide beam for experiments at the end of this JFY Power Receiving Station Booster Tunnel 17/May/2011 Pisa Seminar 2011

  8. mu-e conversion physics introduction 17/May/2011 Pisa Seminar 2011

  9. LFV diagram in SUSY LFV diagram in Standard Model Large top Yukawa coupling ∝ (mν/mW)4 m i x i n g ~ ~ m i x i n g μ e ν ν μ e μ e µ e ~ B W IntroductionLepton Flavour Violation of Charged Leptons Neutrino Mixing (confirmed) ν ν ν Very Small (10-52) μ τ e e μ τ ? ? Charged Lepton Mixing (not observed yet) Sensitive to new Physics beyond the Standard Model 17/May/2011 Pisa Seminar 2011

  10. − , − ( , e ) A Z e ( ) A Z e − ( N N ) μ  − Γ μ − − ν ν μ + + = B ( N e N ) μ − − ' Γ ( N N ) μ − ν What is μ-e Conversion ? 1s state in a muonic atom Neutrino-less muon nuclear capture (=μ-e conversion) nucleus  − μ lepton flavors changes by one unit muondecay in orbit nuclear muon capture  ν  ( , ) ( , 1 ) A Z A Z  − μ + + − μ  17/May/2011 Pisa Seminar 2011

  11. μ-e conversion Signal • Eμe ~ mμ-Bμ • Bμ: binding energy of the 1s muonic atom • Comparison with μeγ (and μ3e) from the view point of experimental technique • Improvement of a muon beam is possible, both in purity (no pions) and in intensity (thanks to muon collider R&D). A higher beam intensity can be taken because of no accidentals. • Potential to discriminate different models through studying the Z dependence R.Kitano, M.Koike, Y.Okada P.R. D66, 096002(2002) 17/May/2011 Pisa Seminar 2011

  12. Z’ Z’ μeγ and μ-e conversion • If μeγ exits, μ-e conv must be • Even if μeγ is not observed, μ-e conv may be • Loop vs Tree • Searches at LHC 17/May/2011 Pisa Seminar 2011

  13. What can we learn from cLFV search? • Mass matrix information of SUSY sleptons • Off-diagonal components • How SUSY is breaking? • What kind of LFV interactions at GUT scale? 17/May/2011 Pisa Seminar 2011

  14. @ Planck mass scale SUSY-GUT Yukawa interaction SUSY Seesaw Model Neutrino Yukawa interaction CKM matrix Neutrino oscillation SUSY-GUT and Seesaw LFV L.J.Hall,V.Kostelecky,S.Raby,1986;A.Masiero, F.Borzumati, 1986 17/May/2011 Pisa Seminar 2011

  15. ~10 Hep-ph/0607263v2 S.Antusch et al hep-ph/0703035v2 G.Isidori et al |δ12LL| = 10−4 and |δ23LL| = 10−2 300 GeV ≤ M~ℓ ≤ 600 GeV 200 GeV ≤ M2 ≤ 1000 GeV 500 GeV ≤ μ ≤ 1000 GeV 10 ≤ tan β ≤ 50 AU = −1 TeV M˜q = 1.5 TeV. and the GUT relations. B-physics constraints case shown in red Current Bound This Experiment This Experiment 0.002 cLFV Search and ν oscillation, g-2 17/May/2011 Pisa Seminar 2011

  16. 0νββ and μ-e conversion RPV-SUSY • V. Cirigliano et al. PRL 93, 231802 (04) • R=B(μe)/B(μeγ) • RPV-SUSY • R >> 10-2 • LRSM (Left-Right Symmetric Model) • R~O(1) • Important to measure R to extract m0νββ from Γ0νγγ LRSM 17/May/2011 Pisa Seminar 2011

  17. MEG at PSI Status • Physics data production started in 2008 • Current published limit Br(μeγ)<2.8x10-11 (at 90% C.L.)　(MEGA world record 1.2x10-11) • Probability to obtain this limit given the average expected limit of 1.3x10-11 is 5% • Will reach the MEGA limit with 2009 data and go further in 2010-2011 Event Distribution in 90% Box 17/May/2011 Pisa Seminar 2011

  18. The SINDRUM-II Experiment (at PSI) Published Results SINDRUM-II used a continuous muon beam from the PSI cyclotron. To eliminate beam related background from a beam, a beam veto counter was placed. 17/May/2011 Pisa Seminar 2011

  19. The MECO Experiment at BNL Cancelled in 2005 The MELC and MECO Proposals • MELC (Russia) and then 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 mu2e @ Fermilab 17/May/2011 Pisa Seminar 2011

  20. Fermilab Accelerators Mu2E @ Fermilab • The mu2e Experiment at Fermilab. • Proposal has been submitted. • CD-1 approval • After the Tevatron shut-down • uses the antiproton accumulator ring • the debuncher ring to manipulate proton beam bunches 17/May/2011 Pisa Seminar 2011

  21. C. Bhat and M. Syphers Mu2e Acc WG meeting Mar 9, 2010 17/May/2011 Pisa Seminar 2011

  22. cLFV Search Experiment • cLFV search is as important as high-energy frontier experiments (and ν oscillation measurements) to find a clue to understand • SUSY-GUT • Neutrino See-saw • MEG is expected to reach and go beyond the current limit pretty soon • Need other experiment(s) to confirm it • Using “different” physics process (with better sensitivity if possible)! • COMET (COherent Muon Electron Transition) • Submitted a proposal to J-PARC in 2008 and a CDR in 2009, • and obtained Stage-1 approval in July 2009 • TDR in preparation, will be published in 2011 17/May/2011 Pisa Seminar 2011

  23. An Experimental Search For Lepton Flavor Violating • μ-- e- Conversion at Sensitivity of 10-16 • http://comet.phys.sci.osaka-u.ac.jp COMET 17/May/2011 Pisa Seminar 2011

  24. Collaboration 17/May/2011 Pisa Seminar 2011

  25. Overview of the COMET Experiment • Proton Beam • pπμ • 8GeV, ~7μA • The Muon Source • Proton Target • Pion Capture • Muon Transport • The Detector • Muon Stopping Target • Electron Transport • Electron Detection 17/May/2011 Pisa Seminar 2011

  26. Proton BEAM 17/May/2011 Pisa Seminar 2011

  27. Requirements for the Beam • Backgrounds • Beam Pion Capture • π-+(A,Z)  (A,Z-1)* γ + (A,Z-1) γ e+ e- • Prompt timing good Extinction! • μ- decay-in-flight, e- scattering, neutron streaming • Requirements from the experiment • Pulsed • High purity • Intense and high repetition rate πμν 0.88μs nuclei μ− μ-e conv 17/May/2011 Pisa Seminar 2011

  28. 1.3 or 1.7μs 100ns 0.7 second beam spill 1.5 second accelerator cycle Requirements for the Proton Beam • Proton beam structure for the mu-e conversion search • 100nsec bunch width, 1.3 (or 1.7) μsec bunch-bunch spacing • 8GeV to suppress anti-proton background • < 1011 proton/bunch, limited by the detector performance • Repetition rate as high as possible within tolerable CR background • Extinction • Residual protons in between the pulses should be < 10-9 Nbg = NP x Rext x Yπ/P x Aπx Pγ x A NP : total # of protons (~1021) Rext : Extinction Ratio (10-9) Yπ/P : π yield per proton (0.015) Aπ : π acceptance (1.5 x 10-6) Pγ : Probability of γ from π (3.5x10-5) A : detector acceptance (0.18) BR=10-16, Nbg ~ 0.1 Extinction < 10-9 Extraction Acceleration 17/May/2011 Pisa Seminar 2011

  29. J-PARC Proton Acceleration for COMET 1.7μs • RCS: h=2 with one empty bucket • MR:h=8(9) with 4(3) empty buckets • Bunched slow extraction • Slow extraction with RF cavity ON 3 batch injection Realization of an empty bucket in RCS by using the chopper in Linac • Simple solution • No need of hardware modification • Heavier heat load in the scraper • Possible leakage of chopped beam in empty buckets 17/May/2011 Pisa Seminar 2011

  30. Double Kick Injection to MR • Sweeping proton leakage in empty buckets • caused by pulse formation inefficiency before LINAC acceleration • Kick injected bunches again after a single turn with a delayed phase by a half cycle • Sweep out the residual particles in the empty bucket After single turn 17/May/2011 Pisa Seminar 2011

  31. Double Kick Injection Performance • Measurement using an abort-line monitor • Installed inside the beam pipe of the MR abort line • Diagnose the beam longitudinal (time) structure • Wide dynamic range • 4 PMTs viewing a single scintillator plate • Different light attenuation using ND filters • Improving factor < 10-6 Normal Injection Double-kick Injection

  32. Muon/pion production 17/May/2011 Pisa Seminar 2011

  33. Pion Production Target • low-E pions • for low-E muons to stop • Backward extraction • pion yield is proportional to Tproton • pion yld is proportional to Beam Power • Target material • High-Z Metal Rod like tungsten or gold • Water cooling • Graphite • Helium gas cooling Target radius optimization 17/May/2011 Pisa Seminar 2011

  34. Pion Capture MARS simulation • > 5 T at the target position • capture pt < 120 MeV/c • Radiation Shield< 100 W on SC coil • 3-4 kW @ target • 35 kW @ W Shield • 2x10-5 W/g @ coil • Yields • 0.05(π+μ)/8-GeV-proton 0 2 4 6 8 10 12 14 16 18 20 17/May/2011 Pisa Seminar 2011 μ-yield vs. Bmax

  35. π-Capture Solenoid • Heat-load density : 2 x 10-5 W/g behind W shield • Utilize Al stabilized SC cable to reduce a heat load to the cold mass. • Cable dimension: 15mm x 4.7mm Al-SC: one of world leading expertise of KEK 17/May/2011 Pisa Seminar 2011

  36. Muon transport 17/May/2011 Pisa Seminar 2011

  37. Muon Transport Guide π’s until decay to μ’s • Suppress high-p particles • μ’s : pμ < 75 MeV/c • e’s : pe < 100 MeV/c Beam Blocker Beam collimator 17/May/2011 Pisa Seminar 2011

  38. High-p Suppression • A center of helical trajectory of charged particles in a curved solenoidal field is drifted by • This effect can be used for charge and momentum selection. • This drift can be compensated by an auxiliary field parallel to the drift direction See “Classical Electrodynamics”, J.D.Jackson Ch.12-Sec.4 δp/δx = 1 MeV/c/cm 17/May/2011 Pisa Seminar 2011

  39. Spectra at the End of the Muon Transport Spectra at the end of the beamline (top left) total momentum (top right)pt vs pL (bottom left) time of flight (bottom right) beam profile . • Preliminary beamline design • main magnetic field • compensation field • Inner radius of transport magnet cryostat (175 mm) • Transport Efficiency 75 MeV/c Dispersion on the muon beam just before the collimator. 17/May/2011 Pisa Seminar 2011

  40. The COMET Detector 17/May/2011 Pisa Seminar 2011

  41. The COMET Detector under a solenoid magnetic field. to detect and identify 100 MeV electrons. to stop muons in the muon stopping target to eliminate low-energy beam particles and to transport only ~100 MeV electrons. 17/May/2011 Pisa Seminar 2011

  42. Muon Stopping Target • Light material for delayed measurement (1st choice) • Aluminum : τμ- = 0.88 μs • Thin disks to minimize electron energy loss in the target • R = 100 mm, 200μmt, 17 disks, 50 mm spacing • Graded B field for a good transmission in the downstream curved section. • Good μ-Stopping efficiency: ε=0.66 • Muon rate 1.5x1011/sec • stopped-muon yields:~0.0023 μ’s/proton 17/May/2011 Pisa Seminar 2011

  43. Curved Solenoid Spectrometer 60-MeV/c DIO electrons • Torus drift for rejecting low energy DIO electrons. • rejection ~10-6: < 10kHz • Good acceptance for signal electrons (w/o including event selection and trigger acceptance) • 20% 105-MeV/c μ-e electron 17/May/2011 Pisa Seminar 2011

  44. Electron Detectors • Rate < 800 kHz • Straw-tube tracker to measure electron momentum • 5 Planes with 48cm distance, σp = 230 keV/c • One plane has 2 views (x and y) with 2 layers per view. • A straw tube has 25mm thick, 5 mm diameter. • should work in vacuum and under a magnetic field. • <500μm position resolution. • Crystal calorimeter for Trigger • GSO, PWO, LYSO, or new crystals … 17/May/2011 Pisa Seminar 2011

  45. Experimental SpaceA possible layout • Discussion in the task force • Target and beam dump outside the hall • Share the upstream proton transport line with the high p beam line • External extinction device in the switch yard 17/May/2011 Pisa Seminar 2011

  46. Signal Sensitivity 2x107 sec running • Single event sensitivity • Nμ is a number of stopping muons in the muon stopping target. It is 2.0x1018 muons. • fcap is a fraction of muon capture, which is 0.6 for aluminum. • Ae is the detector acceptance, which is 0.031. 90% C.L. upper limit 6.0 x 10-17 Single event sensitivity 2.6 x 10-17 17/May/2011 Pisa Seminar 2011

  47. Background Estimation Summary Assuming proton beam extinction < 10-9 17/May/2011 Pisa Seminar 2011

  48. R&D Status 17/May/2011 Pisa Seminar 2011

  49. R&D Status • Straw-tube tracker • Done by Osaka group for MECO • Crystal calorimeter • Transport Solenoid • Extinction Measurement • Device R&D • Gas Cherenkov + Gated PMT • Extinction measurement at J-PARC MR 17/May/2011 Pisa Seminar 2011

  50. Straw-tube Tracker R&D • Prototype Straw-tube chamber • Seamless type tube (I.S.T.) • Thickness : 25 μm • Diameter : 5mm • Material : polyimide+carbon • Resistance : 6MΩ/sq • ASIC design for readout electronics is going with KEK electronics group Beam test using 2.0GeV/c pion beam in 2002 17/May/2011 Pisa Seminar 2011

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