1. The MECO Experiment Coherent µ  e Conversion in the Field of a Nucleus P. Yamin, BNL

2. 6/6/03P. Yamin, BNL NuFact032 MECO Collaboration 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, O. Rind Brookhaven National Laboratory K. Brown, M. Brennan, G. Greene, L. 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, L. S. Pinsky, J. Wilson University of Massachusetts, Amherst K. Kumar

3. 6/6/03P. Yamin, BNL NuFact033 Capture on Nucleus: µ - N(Z,A)  µ N(Z-1,A) Decay in Orbit: µ -  µ e - e Coherent conversion is µ - N(Z,A)  e - N(Z,A), and the signal is a monoenergetic electron. When a muon stops in matter, the principal interactions are: We will measure: R µe =  [µ - N(Z,A)  e - N(Z,A)]/  [µ - N(Z,A)  µ N(Z-1,A)] A single event implies R µe > 2  10 -17.

4. 6/6/03P. Yamin, BNL NuFact034 1. K L  µe 4.7 x 10 -12 D. Ambrose, et al., PRL 81, 5734 (1998) 2. K L  π 0 µe 3.2 x 10 -10 P. Krolek, et al., Phys Lett. B 320, 407 (1994) 3. K +  π + µe 2.1 x 10 -10 A. M. Lee, et al., PRL 64, 165 (1990) 4. µ +  e + e + e - 1.0 x 10 -12 U. Bellgardt, et al., Nucl. Phys B299, 1 (1999) 5. µ +  e + γ 1.2 x 10 -11 M. L. Brooks, et al., PRL 83, 1521, (1999) 6. µ - N  e - N 6.1 x 10 -13 F. Riepenhausen, in Proceedings of the Sixth Conference on the Intersections of Particle and Nuclear Physics, T.W. Donnelly, ed. (AIP, New York, 1997), p. 34. Limits on Lepton Flavor-Violating Processes

5. 6/6/03P. Yamin, BNL NuFact035 What might we expect? Compositeness Second Higgs Heavy Z’, Anomalous Z coupling Predictions at 10 -15 Supersymmetry Heavy Neutrinos Leptoquarks After W. Marciano

6. 6/6/03P. Yamin, BNL NuFact036 Supersymmetry Predictions for   e From Hall and Barbieri Large t quark Yukawa couplings imply observable levels of LFV in supersymmetric grand unified models Extent of lepton flavor violation in Supersymmetry related to quark mixing Other diagrams calculated by Hisano, et al. 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

7. 6/6/03P. Yamin, BNL NuFact037 Previous Experiment—SINDRUM II 1.2  10 7 µ - /sec 6  10 5 π - /sec 2.4  10 3 e - /sec Prompt backgrounds removed by timing, but we want to increase beam intensity by a factor of ~ 1000.  pulsed beam.

8. 6/6/03P. Yamin, BNL NuFact038 Backgrounds 1. Muon Decay in Orbit E max =E conversion, when  s carry no energy. dN/dE e  (Emax – E) 5 Resolution: 900 keV FWHM 2. Radiative µ Capture, µ - N(Z)    N(Z-1)γ For Al, E γ max = 102.5 MeV/c 2, P(E γ > 100.5 MeV/c 2 ) = 4 x 10 -9 P(γ  e + e -, E e >100.5 MeV/c 2 )=2.5 x 10 -5 Endpoint in Al: 105.1 MeV/c 2

9. 6/6/03P. Yamin, BNL NuFact039 Backgrounds, cont’d. 3. Radiative π Capture P(E  >105 MeV/c 2 ) ~ 0.01 P(  e + e -, 103.5<E e <100.5 MeV/c 2 )=3.5  10 -5 beam extinction <10 -9 4. µ Decay in Flight and e - Scatter in Stopping Target: beam extinction 5. Beam e - Scattering in Stopping Target: beam extinction 6. Antiproton Induced e - : thin stopping window 7. Cosmic Ray Induced e - : active and passive shielding

10. 6/6/03P. Yamin, BNL NuFact0310 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 Heat & Radiation Shield Based on MELC design: 4 x 10 13 incident p/sec 1 x 10 11 stopping µ/sec

11. 6/6/03P. Yamin, BNL NuFact0311 The MECO Proton Beam Two of six rf buckets filled, giving 1.35 µsec separation between pulses for a 2.7 µsec rotation time. AGS cycle time is 1 sec. Extinction must be >10 9 ; fast kicker in transport will divert beam from production solenoid; extinction can be monitored. There’s work to be done. 2  10 13 protons/bucket is twice the present AGS bunch intensity. In preliminary tests, extinctions of ~ 10 7 have been achieved. Pulsed beam from AGS to eliminate prompt backgrounds

12. 6/6/03P. Yamin, BNL NuFact0312 The MECO Muon Beam & Transport Solenoid Sign and momentum select in curved solenoid section. (Curvature eliminates direct photon transport.) Collimators absorb antiprotons, low momentum and positive particles. µ spectrum stopping µ spectrum stopping target

13. 6/6/03P. Yamin, BNL NuFact0313 MECO Detector Solenoid Graded field in front section to increase acceptance and reduce cosmic ray background Uniform field in spectrometer region to minimize corrections in momentum analysis Tracking detector downstream of target to reduce rates 1T 2T Electron Calorimete r Tracking Detector Stopping Target: 17 layers of 0.2 mm Al

14. 6/6/03P. Yamin, BNL NuFact0314 Meco Detector Elements Magnetic spectrometer measures electron momentum with precision of 0.3% (rms)—essential to eliminate decay in orbit background. Consists of ~2800 axial straw tube detectors 2.6 m x 5 mm. 250 µm wall thickness. ~2000 element PbWO 4 (3 x 3 x 12 cm) calorimeter measures electron energy to ~5%, providing trigger and confirming trajectory. Electron starts here. Position resolution: 0.2 mm transversely, 1.5 mm axially

15. 6/6/03P. Yamin, BNL NuFact0315 Spectrometer Performance Performance calculated using Monte Carlo simulation of all physical effects Resolution dominated by multiple scattering in tracker Resolution function of spectrometer convolved with theoretical calculation of muon decay in orbit to get expected background. 55, 91, & 105 MeV e - from target

16. 6/6/03P. Yamin, BNL NuFact0316 Where are we? (Funding) RSVP is in NSF budget, beginning in FY06; 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)

17. 6/6/03P. Yamin, BNL NuFact0317 Where are we? (R&D) Water-cooled production target prototype tested, but not in beam. Longitudinal straw tracker prototypes, including electronics, produced; transverse tracker design under consideration. Prototyping of PbWO 4 calorimeter, including APD readout. Cosmic ray shield scintillator prototypes. With additional R&D support, AGS beam studies and design for rf modulated magnet. Conceptual design study for solenoids completed by MIT PSFC; soliciting bids for full engineering design. Design and Prototype

18. 6/6/03P. Yamin, BNL NuFact0318 Where are we? (Calorimeter, Straws) First full-length vane prototype (Houston) 3 x 3 x 14 cm PbWO 4 crystal (NYU) 13 x 13 mm RMD APD and 5 x 5 mm Hamamatsu APD Tests in freezer with cosmic ray muons indicate calorimeter resolution at 105 MeV is ~3.3%. Seamless straws (Osaka): 25 µm thick 5 mm diameter polyamide and carbon

19. 6/6/03P. Yamin, BNL NuFact0319 Where are we? (Magnet)

20. 6/6/03P. Yamin, BNL NuFact0320 Where are we? (magnet layout)

21. 6/6/03P. Yamin, BNL NuFact0321 Where are we? (superconducting Coils) SSC cable embedded in copper: 1.5-4.0 kA, < 20 µW/g nuclear heating  Coil build

22. 6/6/03P. Yamin, BNL NuFact0322 Where are we? (magnet structural)

23. 6/6/03P. Yamin, BNL NuFact0323 Expected Sensitivity of the MECO Experiment We expect ~ 5 signal events for 10 7 s (2800 hours) running if 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

24. 6/6/03P. Yamin, BNL NuFact0324 Expected Background in MECO Experiment We expect ~ 0.45 background events for 10 7 s running with sensitivity of ~ 5 signal events for R  e = 10 -16 SourceEventsComments  decay in orbit 0.25 S/N = 20 for R  e = 10 -16 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 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

25. 6/6/03P. Yamin, BNL NuFact0325 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 - SINDRUMI I

26. 6/6/03P. Yamin, BNL NuFact0326 Where will we be >2008? Bill Marciano at annual BNL/HEP Review, 4/03 MECO will be a significant part of the accelerator- based US High Energy physics program towards the end of this decade! http://meco.ps.uci.edu