Yannis K' Semertzidis

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MUON TO ELECTRON CONVERSION Experiment at BNL
Powerful Probe of Physics Beyond the SM
NuFact04 Osaka, 26 July- 1 Aug. 2004

• Yannis K. Semertzidis
• Brookhaven National Laboratory

• LFV Why is it important?
• LFV Experimental Techniques
• MECO Experiment
• Status

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Muon to Electron COnversion (MECO) Experiment

• 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

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!
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Three Generations
Lepton Number is Conserved, But Why?
Y. Okada Large effects are expected in
well motivated SUSY models
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Sensitivity to Different Muon Conversion
Mechanisms
Supersymmetry
Compositeness
Predictions at 10-15
Second Higgs doublet
Heavy Neutrinos
Heavy Z, Anomalous Z coupling
Leptoquarks
After W. Marciano
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Supersymmetry Predictions for m ? e Conversion
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SUSY EDM, MDM and Transition Moments are in Same
Matrix
See talks by J. Miller on Friday in WG4
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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 vacuum2.2
  ?s)
• They get captured by the nucleus
• or they convert to electrons

Ee m? c2 Ebinding
Erecoil 105.6
0.25 0.25 MeV
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History of Lepton Flavor Violation Searches
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?- 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
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SINDRUM 2
Cosmic raybackground
Prompt background
Expected signal
Experimental signature is105 MeV e- originating
ina thin stopping target
Muon decay in orbit
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MECO Requirements

• Increase the muon flux (graded solenoid, MELC
  design)
• Use pulsed beam with lt10-9 extinction in between
• Detect only promising events
• Use cosmic ray veto
• Have excellent momentum resolution

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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
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Sign and Momentum Selection in the Curved
Transport Solenoid
Detection Time
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Stopping Target and Experiment in Detector
Solenoid
1T
Electron Calorimeter
1T
Tracking Detector
2T
Stopping Target 17 layers of 0.2 mm Al
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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

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Spectrometer Performance Calculations
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1.0
?
0.1
FWHM 900 keV
0.01
103 104 105
106
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Calorimeter
PbWO4 crystals cooled to -23 C coupled with
large area avalanche photodiodes meet MECO
requirements, with efficiency 20-30 photo e-/MeV
Estimated
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Expected Sensitivity of the MECO Experiment

• MECO expects 5 signal events for 107 s running
  for Rme 10-16

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Expected Background in MECO Experiment

• MECO expects 0.45 background events for 107 s
  with 5 signal events
  for Rme 10-16

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MECO at Brookhaven National Laboratory
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Extinction at the AGS of BNL

• Need Extinction to 10-9
• Measure it to 10-10

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
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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)

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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 lt10-6 extinction between bucketsand 10-3
  in unfilled buckets
• A second test at 7.4 GeV with a single filled
  bucket found lt10-7 extinction

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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

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Proposal

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

AGS Ring
20TP
20TP
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Detecting electron beam with EO effect
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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.

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MECO Schedule is Magnet Schedule
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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
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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