M UON TO E LECTRON CO NVERSION Experiment at BNL: Powerful Probe of Physics Beyond the SM

1. NuFact04 Osaka, 28 July 2004 MUON TO ELECTRON CONVERSION Experiment at BNL: Powerful Probe of Physics Beyond the SM Yannis K. Semertzidis Brookhaven National Laboratory • LFV: Why is it important? • LFV Experimental Techniques • MECO Experiment • Status

2. Muon to Electron COnversion (MECO) Experiment • Institute for Nuclear Research, Moscow • V. M. Lobashev, V. Matushka • New York University • R. M. Djilkibaev, A. Mincer, P. Nemethy, J. Sculli, A.N. Toropin • Osaka University • M. Aoki, Y. Kuno, A. Sato • University of Pennsylvania • W. Wales • Syracuse University • R. Holmes, P. Souder • College of William and Mary • M. Eckhause, J. Kane, R. Welsh Boston University J. Miller, B. L. Roberts, V. Logashenko Brookhaven National Laboratory K. Brown, M. Brennan, G. GreeneL. Jia, W. Marciano, W. Morse, Y. Semertzidis, P. Yamin University of California, Irvine M. Hebert, T. J. Liu, W. Molzon, J. Popp, V. Tumakov University of Houston E. V. Hungerford, K. A. Lan, B. W. Mayes, L. S. Pinsky, J. Wilson University of Massachusetts, Amherst K. Kumar Need More Collaborators!

3. MECO is searching for the COHERENT conversion of m e in the field of a nucleus (Al). Neutrino Oscillations: Three Generations… Lepton Number is Conserved, But Why? 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 See talks by J. Miller on Friday in WG4…

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. 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

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

9. MECO Requirements • Increase the muon flux (graded solenoid, MELC design) • Use pulsed beam with <10-9 extinction in between • Detect only promising events • Use cosmic ray veto • Have excellent momentum resolution

10. 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 Heat & Radiation Shield

11. Sign and Momentum Selection in the Curved Transport Solenoid Detection Time

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

13. 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

14. Spectrometer Performance Calculations 10 1.0  0.1 FWHM~900 keV 0.01 103 104 105 106

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

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

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

18. MECO at Brookhaven National Laboratory

19. Need Extinction to 10-9 • Measure it to 10-10 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 Extinction of 10-9 20TP

20. What is Planned for the AGS Ring • 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)

21. 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

22. 1.35 s 1.35 s At the Extraction Beamline we want to measure the extinction • Preliminary design: “Kick” the beam with a sign wave • Alternatively: “Kick” the beam with square wave

23. Measure the extinction in the AGS tunnel to 10-10 Using Electro-optic techniques. • The electric field at 1cm away from the beam is Proposal: AGS Ring 20TP 20TP

24. Detecting electron beam with EO effect

25. Proposal to use a Fabry-Perot Resonator • 2cm long Fabry-Perot cavity • 1000 reflections • Possible to observe extinction to 10-10 by averaging the signal within the 1s machine cycle.

26. MECO Schedule is Magnet Schedule

27. Where are we? (Funding) RSVP is in NSF budget, beginning in FY06 FY05; MECO represents about 60% of its capital cost. NSF FY04 budget submission “I can say that RSVP is now the highest priority construction project from the division of Mathematical and Physical Sciences….” (R. Eisenstein to J. Sculli, 1/29/02) http://meco.ps.uci.edu

28. Enthusiasm within the HEP Community • MECO endorsed by the HEPAP P5 subpanel on long-range planning • MECO endorsed by the recent Drell subpanel identifying 21st century physics challenges as addressing two of the nine questions they identified