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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
Contributions to the Signal Rate Factor
Running time (s) 107
Proton flux (Hz) (50% duty factor, 740 kHz micropulse) 41013
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 efficiency 0.90
Fitting and selection criteria efficiency 0.19
Detected events for Re = 10-16 5.0
Expected Background in MECO ExperimentMECO expects ~0.45 background events for 107 s with
~ 5 signal events for Re = 10-16
Source Events Comments
decay in orbit 0.25 Dominant background
Tracking errors < 0.006
Radiative decay < 0.005
Beam e- < 0.04
decay in flight < 0.03 Without scattering in stopping target
decay in flight 0.04 With scattering in stopping target
decay in flight < 0.001
Radiative capture 0.07 From out of time protons
Radiative capture 0.001 From late arriving pions
Anti-proton induced 0.007 Mostly from
Cosmic ray induced 0.004 Assuming 10-4 CR veto inefficiency
Total Background 0.45 Assuming 10-9 inter-bunch extinction
MECO at Brookhaven National Laboratory
•Need Extinction to 10-9
•Measure it to 10-10
Extinction at the AGS of BNL
Use 6 buckets, only two of them filled with beam. Time between filled buckets: s
AGS Ring20TP
20TP Extinction of 10-9
MeasurementTime
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 bucketsand 10-3 in unfilled buckets
•A second test at 7.4 GeV with a single filled bucket found <10-7 extinction
ma
gn
etic kick
AC magnet
At the Extraction Beamline we want to measure the extinction
• Preliminary design: “Kick” the beam with a sign wave s
s
• Alternatively: “Kick” the beam with square wave
Measure the extinction in the AGS tunnel to 10-10 Using Electro-optic techniques.The electric field at 1cm away from the beam is
Proposal:
AGS Ring
20TP20TP
13 19 8
12 20
2 10 1.6 10 / / 100 3 10 //
2 2 8.85 10 / 10
0.2 /
p C p ns m sQ LE
r F m m
E MV m
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 10-10 by averaging the signal within the 1s machine cycle.
MECO Schedule is Magnet Schedule
MilestoneTarget Month
Issue draft magnet (RFP/RFI) June `04
Issue final magnet RFP Nov `04
Award magnet design, fabrication, installation and acceptance testing contract
June `05
Complete final design June `06
Ship first magnet cryostat to BNL Dec. `07
All acceptance testing complete Dec. `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)
http://meco.ps.uci.edu
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