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

2. Muon to Electron COnversion (MECO) Experiment Boston University R. Carey, V. Logashenko J. Miller, B. L. Roberts, Brookhaven National Laboratory K. Brown, M. Brennan, G. Greene L. 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 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

3. Three Generations… leptonsquarks G=1e e ud G=2  cs G=3  tb Lepton Number is Conserved… MECO is searching for the COHERENT conversion of  e in the field of a nucleus (Al, Ti). Neutrino Oscillations: Y. Okada: “Large effects are expected in well motivated SUSY models”

4. Sensitivity to Different Muon Conversion Mechanisms Compositeness Second Higgs doublet Heavy Z’, Anomalous Z coupling Predictions at 10 -15 Supersymmetry Heavy Neutrinos Leptoquarks After W. Marciano

5. Supersymmetry Predictions for   e Conversion Process Current Limit SUSY level 10 -12 10 -15 10 -11 10 -13 10 -6 10 -9 100 200 300 100 200 300 MECO single event sensitivity 10 -11 10 -13 10 -15 10 -19 10 -17 10 -21 ReRe

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

7. 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: E e = m  c 2 – E binding – E recoil = 105.6 – 0.25 – 0.25 MeV

8. We want to measure R  e with Sensitivity: High Proton Flux, High Muon Collection Efficiency, goal: ~10 11 muon stops/sec High Background Rejection, High Extinction Need

9. 1 10 -2 10 -4 10 -16 10 -6 10 -8 10 -10 10 -14 10 -12 1940 1950 1960 1970 1980 1990 2000 2010 MECO Goal  History of Lepton Flavor Violation Searches  - N  e - N  +  e +   +  e + e + e - K 0    + e - K +    +  + e - E871 SINDRUM2 PSI-MEG Goal  MEGA

10. SINDRUM 2 Expected signal Prompt backgroun d Muon decay in orbit Cosmic ray backgroun d Experimental signature is 105 MeV e - originating in a thin stopping target

11. 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

12. Number of  - per Interaction Comparison with Data… GHEISHA DATA GCALOR FLUKA Kinetic Energy [GeV] Pions/GeV Prediction for MECO Beam By V. Tumakov

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

14. Charged particle’s helix conserves flux… R 2  B is constant i.e. in a graded solenoid transverse momentum is transformed into longitudinal increasing its collection efficiency. is constant too,

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

16. 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 transit time trajectories Muon Beam Transport with Curved Solenoid 2.5T 2.4T 2.1T 2.0T 2.4T

17. Sign and Momentum Selection in the Curved Transport Solenoid

18. e-e- -- e+e+ ++ Time [ns] Momentum and Time Distributions in MECO Muon Beam Relative Flux Momentum [MeV/c] e-e+e-e+ Particles/proton/ns

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

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

21. 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 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 Electron starts upstream, reflects in field gradient

22. 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

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

24. Calorimeter Estimated PbWO 4 crystals cooled to -23 °C coupled with large area avalanche photodiodes meet MECO requirements, with efficiency 20-30 photo e - /MeV

25. Expected Sensitivity of the MECO Experiment MECO expects ~ 5 signal events for 10 7 s running for R  e = 10 -16 Contributions to the Signal RateFactor Running time (s)10 7 Proton flux (Hz) (50% duty factor, 740 kHz micropulse) 4  10 13  entering transport solenoid / incident proton 0.0043  stopping probability 0.58  capture probability 0.60 Fraction of  capture in detection time window 0.49 Electron trigger efficiency0.90 Fitting and selection criteria efficiency0.19 Detected events for R  e = 10 -16 5.0

26. Expected Background in MECO Experiment MECO expects ~0.45 background events for 10 7 s with ~ 5 signal events for R  e = 10 -16 SourceEventsComments  decay in orbit 0.25 Dominant background; resolution Tracking errors< 0.006 Radiative  decay < 0.005 Beam e - < 0.04  decay in flight < 0.03Without scattering in stopping target  decay in flight 0.04With scattering in stopping target  decay in flight < 0.001 Radiative  capture 0.07From out of time protons; extinction Radiative  capture 0.001From late arriving pions Anti-proton induced0.007 Mostly from   Cosmic ray induced0.004Assuming 10 -4 CR veto inefficiency Total Background0.45Assuming 10 -9 inter-bunch extinction

27. Required Extinction vs Time

28. MECO at Brookhaven National Laboratory

29. Extinction of 10 -9 Extinction at the AGS of BNL Use 6 buckets, only two of them filled with beam. Time between filled buckets:  s AGS Ring 20TP Extinction of 10 -9 Measurement Time

30. 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) Mike Brennan (1998)  s

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

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

33. 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…

34. Coasting bucket Accelerated bucket Preventing Bucket Contamination:

35. 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”.

36. RSVP/MECO Milestones Milestone Cost BaselineApril `05 HEPAP review 2005 $15M for FY2005 for RSVP, available after baseline/HEPAP review decisions President’s request for RSVP for FY2006$42M Start data taking2011