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Large Acceptance and High Extinction Pion/Muon Beamline for the MECO Experiment at BNL

MSI-05 KEK, 1-4 March 2005. Large Acceptance and High Extinction Pion/Muon Beamline for the MECO Experiment at BNL. Yannis K. Semertzidis Brookhaven National Laboratory. LFV: Physics Reach LFV Experimental Techniques MECO Experiment at BNL Intensity, Collection Efficiency

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Large Acceptance and High Extinction Pion/Muon Beamline for the MECO Experiment at BNL

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  1. MSI-05 KEK, 1-4 March 2005 Large Acceptance and High Extinction Pion/Muon Beamline for the MECO Experiment at BNL Yannis K. Semertzidis Brookhaven National Laboratory • LFV: Physics Reach • LFV Experimental Techniques • MECO Experiment at BNL • Intensity, Collection Efficiency • Extinction Issues

  2. Muon to Electron COnversion (MECO) Experiment • University of Massachusetts, Amherst • K. Kumar • Institute for Nuclear Research, Moscow • V. M. Lobashev, V. Matushko • New York University • R. M. Djilkibaev, A. Mincer, P. Nemethy, J. Sculli • Osaka University • M. Aoki, Y. Kuno, A. Sato • University of Virginia • C. Dukes, K. Nelson, A. Norman • Syracuse University • R. Holmes, P. Souder • College of William and Mary • M. Eckhause, J. Kane, R. Welsh Boston University R. Carey, V. Logashenko J. Miller, B. L. Roberts, Brookhaven National Laboratory K. Brown, M. Brennan, G. GreeneL. Jia, W. Marciano, W. Morse, P. Pile, Y. Semertzidis, P. Yamin Berkeley Y. Kolomensky University of California, Irvine C. Chen, M. Hebert, P. Huwe, W. Molzon, J. Popp, V. Tumakov University of Houston Y. Cui, N. Elkhayari, E. V. Hungerford, N. Klantarians, K. A. Lan

  3. MECO is searching for the COHERENT conversion of m e in the field of a nucleus (Al, Ti). Neutrino Oscillations: Three Generations… Lepton Number is Conserved… Y. Okada: “Large effects are expected in well motivated SUSY models”

  4. 10 -11 10 -13 Re 10 -15 10 -17 10 -19 MECO single event sensitivity 10 -21 100 200 300 100 200 300 Supersymmetry Predictions for m e Conversion

  5. SUSY: EDM, MDM and Transition Moments are in Same Matrix

  6. Experimental Method • Low energy muons are captured by a target nucleus. They cascade to 1s state rapidly. • They either decay in orbit: with a lifetime of ~0.9s for Al (in vacuum:2.2 s) • They get captured by the nucleus: • or …they convert to electrons: Ee = mc2 – Ebinding – Erecoil = 105.6 – 0.25 – 0.25 MeV

  7. We want to measure Re with Sensitivity: • High Proton Flux, High Muon Collection Efficiency, goal: ~1011muon stops/sec • High Background Rejection, High Extinction Need

  8. History of Lepton Flavor Violation Searches 1 - N  e-N +  e+ +  e+ e+ e- 10-2 10-4 10-6 10-8 MEGA 10-10 E871 10-12 K0 +e-K+ + +e- SINDRUM2 PSI-MEG Goal  10-14 10-16 MECO Goal  1940 1950 1960 1970 1980 1990 2000 2010

  9. SINDRUM 2 Cosmic raybackground Prompt background Expected signal Experimental signature is105 MeV e- originating ina thin stopping target Muon decay in orbit

  10. MECO Requirements • Increase the muon flux (graded solenoid, MELC design), collect ~10-2 muons/proton • Use pulsed beam with <10-9 extinction in between for prompt background rejection • Detect …only promising events defines detector geometry; resolution requirements • Use cosmic ray veto

  11. Number of p- per InteractionComparison with Data… Pions/GeV By V. Tumakov Prediction for MECO Beam GHEISHA DATA GCALOR FLUKA Kinetic Energy [GeV]

  12. The MECO Apparatus Straw Tracker Muon Stopping Target Muon Beam Stop Superconducting Transport Solenoid (2.5 T – 2.1 T) Crystal Calorimeter Superconducting Detector Solenoid (2.0 T – 1.0 T) Superconducting Production Solenoid (5.0 T – 2.5 T) Muon Production Target Collimators Proton Beam Proton Beam

  13. Charged particle’s helix conserves flux… R2B is constant i.e. in a graded solenoid transverse momentum is transformed into longitudinal increasing its collection efficiency. is constant too,

  14. Production region Magnetic field vs distance Magnetic Field Overview 5T Curved sections Curved sections Detector region • Curved sections 3T 1T At 3.3 Tesla: 75% of muon capture efficiency of 5 Tesla. 0 10 20 Distance along beam path [m]

  15. 2.5T 2.4T 2.4T 2.1T 2.1T 2.0T Muon Beam Transport with Curved Solenoid Goals: • Transport low energy -to the detector solenoid • Minimize transport of positive particles and high energy particles • Minimize transport of neutral particles • Absorb anti-protons in a thin window • Minimize long transittime trajectories

  16. Sign and Momentum Selection in the Curved Transport Solenoid

  17. Momentum and Time Distributions in MECO Muon Beam Relative Flux Particles/proton/ns e- e+ m- m+ e- e+ m- m+ Time [ns] Momentum [MeV/c]

  18. Transported and stopped muons Transported muon spectrum Stopped muon spectrum

  19. Stopping Target and Experiment in Detector Solenoid 1T Electron Calorimeter 1T Tracking Detector 2T Stopping Target: 17 layers of 0.2 mm Al

  20. Magnetic Spectrometer for Conversion Electron Momentum Measurement • Measures electron momentum with precision of about 0.3% (RMS) – essential to eliminate muon decay in orbit background Electron starts upstream, reflects in field gradient • 2800 nearly axial detectors, 2.6 m long, 5 mm diameter,0.025 mm wall thickness – minimum material to reduce scattering • position resolution of 0.2 mm in transverse direction, 1.5 mm in axial direction

  21. Two Tracking Detector option are being considered • Longitudinal geometry with ~3000 3m long straws • Transverse geometry with ~13000 1.4 m straws Both geometries appear to meet physics requirements Longitudinal Tracker

  22. Spectrometer Performance Calculations 10 Aiming for ~200 KeV resolution 1.0  0.1 FWHM~900 keV 0.01 103 104 105 106

  23. Calorimeter PbWO4 crystals cooled to -23 °C coupled with large area avalanche photodiodes meet MECO requirements, with efficiency 20-30 photo e-/MeV Estimated

  24. Expected Sensitivity of the MECO Experiment MECO expects ~ 5 signal events for 107 s running for Rme = 10-16

  25. Expected Background in MECO Experiment MECO expects ~0.45 background events for 107 s with ~ 5 signal events for Rme = 10-16

  26. Required Extinction vs Time

  27. MECO at Brookhaven National Laboratory

  28. Extinction of 10-9 Extinction at the AGS of BNL Use 6 buckets, only two of them filled with beam. Time between filled buckets: 1.35 s Measurement Time AGS Ring 20TP 20TP Extinction of 10-9

  29. 1.35 s What is Planned for the AGS Ring Mike Brennan (1998) • Use a 60KHz AC Dipole Magnet (CW). Resonance at the vertical betatron frequency • Use a pulsed Strip-line kicker to kick the full buckets into stable orbits. • Need 1-50ms to drive particles off (driven by the strip-line kicker)

  30. Removing Out-of-Bucket Protons in the AGS AC magnet magnetic kick • Extinction measurements: • Initial test at 24 GeV with one RF bucket filled yielded <10-6 extinction between bucketsand 10-3 in unfilled buckets • A second test at 7.4 GeV with a single filled bucket found <10-7 extinction

  31. Buckets at AGS with h=6, W. Glenn Buckets are connected creating unstable fixed points.

  32. One or Two filled buckets? (W.Glenn) • At Injection the proton phase space is large (scales as 1/). While waiting for the second injection (~0.2s) protons hop into the next buckets…

  33. Preventing Bucket Contamination: Coasting bucket Accelerated bucket

  34. We are planning • To study the one vs two filled buckets in the AGS ring with simulation and beam. • Measure extinction in the AGS to 10-9 • Use external monitor and use an external extinction device as “insurance”.

  35. RSVP/MECO Milestones

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