Yannis K. Semertzidis Brookhaven National Laboratory NuFact04 Osaka, 26 July- 1 Aug LFV: Why is it important? LFV Experimental Techniques MECO Experiment Status MUON TO ELECTRON CONVERSION Experiment at BNL: Powerful Probe of Physics Beyond the SM

Muon to Electron COnversion (MECO) Experiment Boston University J. Miller, B. L. Roberts, V. Logashenko 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, B. W. Mayes, L. S. Pinsky, J. Wilson University of Massachusetts, Amherst K. Kumar 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 Need More Collaborators!

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

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

Supersymmetry Predictions for   e Conversion Process Current Limit SUSY level MECO single event sensitivity ReRe

SUSY: EDM, MDM and Transition Moments are in Same Matrix See talks by J. Miller on Friday in WG4…

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 = – 0.25 – 0.25 MeV

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

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

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

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

Sign and Momentum Selection in the Curved Transport Solenoid Detection Time

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

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, 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

Spectrometer Performance Calculations FWHM ~900 keV 

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

Expected Sensitivity of the MECO Experiment MECO expects ~ 5 signal events for 10 7 s running for R  e = Contributions to the Signal RateFactor Running time (s)10 7 Proton flux (Hz) (50% duty factor, 740 kHz micropulse) 4   entering transport solenoid / incident proton  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 =

Expected Background in MECO Experiment MECO expects ~0.45 background events for 10 7 s with ~ 5 signal events for R  e = SourceEventsComments  decay in orbit 0.25 Dominant background Tracking errors< Radiative  decay < 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 < 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 CR veto inefficiency Total Background0.45Assuming inter-bunch extinction

MECO at Brookhaven National Laboratory

Need Extinction to Measure it to 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 Measurement Time

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)

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 in unfilled buckets A second test at 7.4 GeV with a single filled bucket found <10 -7 extinction magnetic kick AC magnet

At the Extraction Beamline we want to measure the extinction Preliminary design: “Kick” the beam with a sign wave  s Alternatively: “Kick” the beam with square wave

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

Detecting electron beam with EO effect

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

MECO Schedule is Magnet Schedule Milestone Target Month Issue draft magnet (RFP/RFI)June `04 Issue final magnet RFPNov `04 Award magnet design, fabrication, installation and acceptance testing contract June `05 Complete final designJune `06 Ship first magnet cryostat to BNLDec. `07 All acceptance testing completeDec. `08

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)

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