素粒子実験領域、素粒子論領域、ビーム物理領域合同シンポジウム μ - e conversion 実験 @J - PARC --- COMET --- Koji Y oshimura, KEK on behalf of COMET collaboration Most slides were inherited from Aoki - san’s talk at JSPS Meeting J - PARC におけるミューオン素粒子物理実験
The COMET Collaboration (as of October 16, 2008) D. Bryman Department of physics and astronomy, University of British Columbia, Vancouver, Canada, R. Palmer Department of Physics, Brookhaven National Laboratory, USA, E. Hungerford Department of Physics, University of Houston, USA Y. Iwashita, Institute for Chemical Research, Kyoto University, Kyoto, Japan V. Kalinnikov, A. Moiseenko, D. Mzhavia, J. Pontecorvo, B. Sabirov, Z. Tsamaiaidze, and P . Evtukhouvich JINR, Dubna, Russia M. Aoki, Y. Arimoto, Md.I. Hossain, T. Itahashi, Y. Kuno, A. Sato, and M. Yoshida Department of Physics, Osaka University, Japan J. Sato, M. Yamanaka Department of Physics, Saitama University, Japan Y, Takubo, Department of Physics, Tohoku University, Japan Y. Igarashi, S. Ishimoto, S. Mihara, H. Nishiguchi, T. Ogitsu, M. Tomizawa, A. Yamamoto, and K. Yoshimura High Energy Accelerator Research Organization (KEK), Japan T. Numao new in red TRIUMF , Canada
The (quasi) COMET Collaborators (not sign in yet but participate in the meetings and even do simulation works.) The COMET collaboration is approaching to .... A. Kurup, (and Y. Uchida) The Blakett Laboratory, Imperial College London, UK T. Ito Los Alamos National Laboratory, USA, for the UK, Oxford University, University College London, Glasgow University and other UK Universities. and is planning a LFV workshop in the UK in November for France, Orsay and Saclay.... and is planning a seminar trip in French institutes in November for Switzerland, ETH Zurich and PSI and is attending a Swiss Workshop in November for Italy, Germany and Spain not yet....
Muon Task Force, Muon Working Group and the COMET collaboration COMET collaboration Muon g-2 Japan Group Muon Working Group (discussing Japanese activities of muon particle physics) KEK Muon Task Force
Contents • Introduction • What is mu - e conversion • Physics of c - LFV ( brief for experimentalist ) • How to measure mu - e conversion • COMET • Pulsed Proton Beam • Pion Production and Capture • Muon T ransport and Muon Stopping Target • Curved Solenoid Spectrometer • Sensitivity and Background • COMET to PRISM • Summary
μ - e Conversion • Muonic Atom ( 1S state ) Muon Capture(MC) µ − Muon Decay in Orbit (MDO) nuclei • MC:MDO = 1:1000 ( H ) , 3:2 ( Al ) , 13:1 ( Cu ) • τ ( free μ -) = 2.2 μ s • τ ( μ - ;Al ) = 0.88 μ s • μ - e Conversion µ − + ( A, Z ) → e − + ( A, Z ) charged Lepton Flavor Violation (c-LFV) Γ [ µ − + ( A, Z ) → e − + ( A, Z )] BR[ µ − + ( A, Z ) → e − + ( A, Z )] ≡ Γ [ µ − + ( A, Z ) → ν µ + ( A, Z − 1)] 6
charged Lepton Flavor Violation • charged Lepton Flavor Violation ( c - LFV ) • Forbidden in the SM • μ - +A → e - +A , μ → e γ , μ → eee, τ → e ( μ ) γ , τ → e ( μ ) h ... • Neutrino - mixing predicts very small amount of c - LFV via higher order diagram; it is as small as practically impossible to observe in foreseeable future. A. de Gouvea • c - LFV = Physics beyond SM with neutrino oscillation 7
Physics of μ - e Conversion • SUSY - GUT, SUSY - seesaw ( Photon Mediated process ) • BR = 10 - 15 = BR ( μ → e γ ) × O ( α ) • τ → l γ • SUSY - seesaw ( Higgs Mediated process ) N N • BR = 10 - 12 ~10 - 15 • τ → l η • Doubly Charged Higgs Boson ( LRS etc. ) • Logarithmic enhancement in a loop diagram for μ - N → e - N, not for μ → e γ • M. Raidal and A. Santamaria, PLB 421 ( 1998 ) 250 • SUSY with R - parity Violation • Leptquarks • Heavy Z’ • Compositeness • Multi - Higgs Models
Physics of μ - e Conversion • SUSY - GUT, SUSY - seesaw ( Photon Mediated process ) • BR = 10 - 15 = BR ( μ → e γ ) × O ( α ) • τ → l γ • SUSY - seesaw ( Higgs Mediated process ) N N • BR = 10 - 12 ~10 - 15 • τ → l η • Doubly Charged Higgs Boson ( LRS etc. ) • Logarithmic enhancement in a loop diagram for μ - N → e - N, not for μ → e γ • M. Raidal and A. Santamaria, PLB 421 ( 1998 ) 250 • SUSY with R - parity Violation • Leptquarks • Heavy Z’ • Compositeness • Multi - Higgs Models
c - LFV and SUSY c - LFV slepton mixing SUSY m 2 ∆ m 2 ∆ m 2 e ˜ ˜ e ˜ ˜ e ˜ ˜ e µ τ ∆ m 2 m 2 ∆ m 2 µ ˜ ˜ µ ˜ ˜ µ ˜ ˜ e µ τ ∆ m 2 ∆ m 2 m 2 τ ˜ ˜ τ ˜ ˜ τ ˜ ˜ e µ τ Physics of slepton mass matrix 9
Theoretical Predictions Current SUSY - GUT SUSY+Seesaw, MSW Large Angle Process Future Limit level µ N → e N 10 - 13 10 - 16 10 - 16 ,10 - 18 tan β =30 tan β =10 tan β =3 µ → e γ 10 - 11 10 - 14 10 - 13 τ → µ γ 10 - 6 10 - 9 10 - 8 SUSY - GUT MEG MEG COMET COMET PRSM/PRIME PRISM/PRIME Courtesy Hisano 10
̃ ̃ ̃ ̃ ̃ ̃ Golden T rio c- LFV g - 2 EDM large top Yukawa coupling � � mixing e e ~ � 0 � 0 B Real Imaginary m 2 ∆ m 2 ∆ m 2 e ˜ ˜ e ˜ ˜ e ˜ ˜ e µ τ ∆ m 2 m 2 ∆ m 2 slepton mass matrix µ ˜ ˜ µ ˜ ˜ µ ˜ ˜ e µ τ ∆ m 2 ∆ m 2 m 2 τ ˜ ˜ τ ˜ ˜ τ ˜ ˜ e µ τ τ - LFV
Principal of Experiment SINDRUM II • Signal : μ - + ( A,Z ) → e - + ( A,Z ) • A single mono - energetic electron • 100 MeV • Delayed ： ~1 μ S • No accidental backgrounds • Physics backgrounds • Muon Decay in Orbit ( MDO ) • Δ E e =350 keV ( BR:10 - 16 ) • Beam Pion Capture • π - + ( A,Z ) → ( A,Z - 1 ) * → γ + ( A,Z - 1 ) γ → e + e - • Prompt timing BR < 7 × 10 - 13 12
COMET @ J - PARC Pion Capture Section • Pulsed Proton Beam A section to capture pions with a large solid angle under a high solenoidal magnetic field by superconducting • π- b.g. suppression maget Production Target • Large μ yields • J - PARC/MR Detector Section A detector to search for only 60 kW out of 450kW muon-to-electron conver- sion processes. • π- capture SC - solenoid Stopping Target • 10 11 μ /s ( PSI:10 8 μ /s ) • Curved - solenoid detector Pion-Decay and Muon-Transport Section • Lower detector rate A section to collect muons from decay of pions under a solenoi- dal magnetic field. • Upgradability to PRISM • add Phase - Rotator - Ring
Physics Capabilities of mu - e J - PARC PAC report about COMET US P5 Report
Pulsed Proton Beam • Backgrounds • π - + ( A,Z ) → ( A,Z - 1 ) * → γ + ( A,Z - 1 ) ， γ → e + e - : Prompt • μ - decay - in - flight, e - scattering, neutron streaming • Signal • μ - + ( A,Z ) → e - + ( A,Z ) : Delayed ( ~1 μ s ) N bg = N P × R ext × Y π /P × A π × P γ × A 100 ns Main Proton Pulse N P : total # of protons ( ~10 21 ) 8 10 p/pulse R ext : Extinction Ratio ( 10 - 9 ) Prompt Background Arbitrary Unit Y π /P : π yield per proton ( 0.015 ) A π : π acceptance ( 1.5 × 10 - 6 ) Stopped Muon Decay P γ : Probability of γ from π ( 3.5 × 10 - 5 ) Timing Window A : detector acceptance ( 0.18 ) Signal BR=10 - 16 , N bg < 0.12 ⇔ Extinction < 10 - 9 0 1 ( s ) μ Time 1.1 μ s
Pulsed Proton@ J - PARC • Tomizawa Scheme • RCS : h=2 w/ empty bucket • MR : Empty bucket Scheme • h=8 • Bunched Slow Extraction → Next talk by Tomizawa - san for details.
Additional Extinction Means 0.05 x (m) Collimator 0.04 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 0.03 • AC - dipole 0.02 B1 B2 0.01 0 − 0 .01 • @ primary beamline − 0 .02 − 0 .03 − 0 .04 − 0 .05 • f extinction ~ 1/100 0 5 10 15 20 25 30 L (m) 0.05 y (m) • collaboration with mu2e 0.04 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 B1 B2 Collimator 0.03 0.02 0.01 0 − 0 .01 − 0 .02 − 0 .03 − 0 .04 − 0 .05 0 5 10 15 20 25 30 L (m) • Bunch Cleaner • in MR • tested at AGS for MECO
Pion Production & Capture Pion Capture Section A section to capture pions with a large solid angle under a high solenoidal magnetic field by superconducting maget Production Target Detector Section A detector to search for muon-to-electron conver- sion processes. Stopping Target Pion-Decay and Muon-Transport Section A section to collect muons from decay of pions under a solenoi- dal magnetic field.
Pion Production • low - E pions • for low - E muons to stop • Backward extraction • pion yield ∝ T proton • pion yield ∝ Beam Power • High - Z Metal Rod • 12 - mm φ × 16 - cm • 3 - 4 kW on the target • W ater cooling or Radiation cooling
Pion Capture MARS simulation -3 80 10 -4 radial position (cm) 10 -5 10 -6 60 10 -7 10 -8 40 10 -9 10 -10 10 -11 20 10 -12 10 -13 0 10 0 100 200 300 z position (cm) Energy deposition (GeV/g/1ppp) • 5 T at the target position • capture p t < 120 MeV/c • Radiation Shield < 100 W on SC coil • 3 - 4 kW @ target • 35 kW @ W Shield • 2 × 10 - 5 W/g @ coil • yields: 0.05 ( π + μ )/8-GeV-proton μ - yield vs. B max
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