Yannis K. Semertzidis Brookhaven National Laboratory NuFact0 4 Osaka, 28 July 2004 •LFV: Why is it important? •LFV Experimental Techniques •MECO Experiment •Status M UON TO E LECTRON CO NVERSION Experiment at BNL: Powerful Probe of Physics Beyond the SM
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Yannis K. Semertzidis Brookhaven National Laboratory NuFact04 Osaka, 28 July 2004 LFV: Why is it important? LFV Experimental Techniques MECO Experiment.
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Yannis K. Semertzidis
Brookhaven National Laboratory
NuFact04 Osaka, 28 July 2004
•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…leptons quarks
G=1 e e u d
G=2 c s
G=3 t b
Lepton Number isConserved, But Why?
MECO is searching forthe COHERENTconversion of ein the field of anucleus (Al).
2
2
2W
m
MRate
Neutrino Oscillations:
Y. Okada: “Large effectsare expected in wellmotivated SUSY models”
Supersymmetry Predictions for e Conversion
ProcessCurrent Limit
SUSY level
10-12 10-15
10-11 10-13
10-6 10-9
+ e
- -N e N
Rem (GeV)
100 200 300 100 200 300
0 0
MECO single event sensitivity
10 -11
10 -13
10 -15
10 -19
10 -17
10 -21
Re
Rem (GeV)
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 ~0.9s for Al (in vacuum:2.2 s)
• They get captured by the nucleus:
• or …they convert to electrons:
N N'(Z-1) [ p n]- -
- -ee
- -e Ee = m c2 – Ebinding – Erecoil
= 105.6 – 0.25 – 0.25 MeV
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-
K0 +e-
K+ + +e-
E871
SINDRUM2PSI-MEG Goal
MEGA
SINDRUM 2
Expected signal
Prompt backgroun
d
Muon decay in orbit
Cosmic raybackgroun
d
Experimental signature is
105 MeV e- originating ina 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
2 2s t
s
1+ p2
p1 sD= × × p0.3B R
Stopping Target and Experiment in Detector Solenoid
1T
1T
2T
Electron Calorimete
r
Tracking DetectorStopping 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,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
Spectrometer Performance Calculations
FWHM ~900 keV
10
1.0
0.1
0.01 103 104 105 106
Calorimeter
/ E 3.5% Estimated
PbWO4 crystals cooled to -23 °C coupled with large area avalanche photodiodes meet MECO requirements, with efficiency 20-30 photo e-/MeV
Expected Sensitivity of the MECO ExperimentMECO expects ~ 5 signal events for 107 s running for Re = 10-16