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The MECO Experiment

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

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The MECO Experiment

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

  2. 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 MECO Collaboration P. Yamin, BNL CIPANP2003

  3. When a muon stops in matter, the principal interactions are: Capture on Nucleus: µ-N(Z,A)  µN(Z-1,A) Decay in Orbit: µ- µe-e Coherent conversion is µ-N(Z,A)  e-N(Z,A), and the signal is a monoenergetic electron . We will measure: Rµe=[µ-N(Z,A)  e-N(Z,A)]/ [µ-N(Z,A)  µN(Z-1,A)] A single event implies Rµe > 2  10-17. P. Yamin, BNL CIPANP2003

  4. Limits on Lepton Flavor-Violating Processes 1. KL µe 4.7 x 10-12D. Ambrose, et al., PRL 81, 5734 (1998) 2. KL  π0µe 3.2 x 10-10P. Krolek, et al., Phys Lett. B 320, 407 (1994) 3. K+  π+ µe 2.1 x 10-10A. M. Lee, et al., PRL 64, 165 (1990) 4. µ+ e+e+e- 1.0 x 10-12U. Bellgardt, et al., Nucl. Phys B299, 1 (1999) 5. µ+ e+γ 1.2 x 10-11M. L. Brooks, et al., PRL 83, 1521, (1999) 6. µ-N  e-N 7.8 x 10-13F. 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. P. Yamin, BNL CIPANP2003

  5. Heavy Neutrinos Heavy Z’, Anomalous Z coupling Leptoquarks What might we expect? Supersymmetry Compositeness Predictions at 10-15 Second Higgs After W. Marciano P. Yamin, BNL CIPANP2003

  6. 10 -11 10 -13 10 -15 10 -17 10 -19 10 -21 Supersymmetry Predictions for m e • From Hall and Barbieri Large t quark Yukawa couplingsimply observable levels of LFV insupersymmetric grand unified models • Extent of lepton flavor violation in Supersymmetry related to quark mixing • Other diagrams calculated by Hisano, et al. Re MECO single event sensitivity 100 200 300 100 200 300 P. Yamin, BNL CIPANP2003

  7. Previous Experiment—SINDRUM II 1.2  107 µ-/sec 6  105 π-/sec 2.4 103 e-/sec Prompt backgrounds removed by timing, but we want to increase beam intensity by a factor of ~ 1000. pulsed beam. P. Yamin, BNL CIPANP2003

  8. Backgrounds 1. Muon Decay in Orbit Emax=Econversion, when s carry no energy. dN/dEe  (Emax – E)5 Resolution: 900 keV FWHM 2. Radiative µ Capture, µ-N(Z)  N(Z-1)γ For Al, Eγmax = 102.5 MeV/c2, P(Eγ> 100.5 MeV/c2) = 4 x 10-9 P(γ  e+e-, Ee>100.5 MeV/c2)=2.5 x 10-5 Endpoint in Al: 105.1 MeV/c2 P. Yamin, BNL CIPANP2003

  9. Backgrounds, cont’d. 3. Radiative π Capture P(E>105 MeV/c2) ~ 0.01 P(e+e-, 103.5<Ee<100.5 MeV/c2)=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 P. Yamin, BNL CIPANP2003

  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 Based on MELC design: 4 x 1013 incident p/sec 1 x 1011 stopping µ/sec Heat & Radiation Shield P. Yamin, BNL CIPANP2003

  11. The MECO Proton Beam Pulsed beam from AGS to eliminate prompt backgrounds 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 >109; fast kicker in transport will divert beam from production solenoid; extinction can be monitored. There’s work to be done. 2  1013 protons/bucket is twice the present AGS bunch intensity. In preliminary tests, extinctions of ~ 107 have been achieved. P. Yamin, BNL CIPANP2003

  12. The MECO Muon Beam & Transport Solenoid stopping target 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 P. Yamin, BNL CIPANP2003

  13. 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 downstreamof target to reduce rates 1T Electron Calorimeter 1T Tracking Detector 2T Stopping Target: 17 layers of 0.2 mm Al P. Yamin, BNL CIPANP2003

  14. 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 PbWO4 (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 P. Yamin, BNL CIPANP2003

  15. Spectrometer Performance 55, 91, & 105 MeV e- from target 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. P. Yamin, BNL CIPANP2003

  16. 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) P. Yamin, BNL CIPANP2003

  17. Where are we? (R&D) Design and Prototype • Water-cooled target prototype tested, but not in beam. • Straw tracker prototypes, including electronics, produced; alternative (transverse) tracker design under consideration. • Prototyping of PbWO4 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. P. Yamin, BNL CIPANP2003

  18. Where are we? (Calorimeter, Straws) 3 x 3 x 14 cm PbWO4 crystal (NYU) 13 x 13 mm RMD APD and 5 x 5 mm Hamamatsu APD First full-length vane prototype (Houston) Seamless straws (Osaka): 25 µm thick 5 mm diameter polyamide and carbon Tests in freezer with cosmic ray muons indicate calorimeter resolution at 105 MeV is ~3.3%. P. Yamin, BNL CIPANP2003

  19. Where are we? (Magnet) P. Yamin, BNL CIPANP2003

  20. Where are we? (magnet layout) P. Yamin, BNL CIPANP2003

  21. Where are we? (superconducting Coils) Coil build SSC cable embedded in copper: 7kA, ~50µW/g nuclear heating P. Yamin, BNL CIPANP2003

  22. Where are we? (magnet structural) P. Yamin, BNL CIPANP2003

  23. Expected Sensitivity of the MECO Experiment We expect ~ 5 signal events for 107 s (2800 hours) running if Rme = 10-16 P. Yamin, BNL CIPANP2003

  24. Expected Background in MECO Experiment We expect ~ 0.45 background events for 107 s running with sensitivity of ~ 5 signal events for Rme = 10-16 P. Yamin, BNL CIPANP2003

  25. History of Lepton Flavor Violation Searches 1 - N  e-N +  e+ +  e+ e+ e- 10-2 10-4 10-6 10-8 10-10 10-12 K0 +e-K+ + +e- SINDRUMII 10-14 10-16 MECO Goal  1940 1950 1960 1970 1980 1990 2000 2010 P. Yamin, BNL CIPANP2003

  26. Where Will we be >2008? MECO will be a significant part of the US High Energy physics program towards the end of this decade! http://meco.ps.uci.edu Bill Marciano at annual BNL/HEP Review, 4/03 P. Yamin, BNL CIPANP2003

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