Muon to Electron COnversion MECO Experiment

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Muon to Electron COnversion (MECO) Experiment

• Boston University
• R. Carey, V. Logashenko
• J. Miller, B. L. Roberts,
• Brookhaven National Laboratory
• K. Brown, M. Brennan, G. GreeneL. Jia, W.
  Marciano, W. Morse, P.
  Pile, Y. Semertzidis, P. Yamin
• Berkeley
• Y. Kolomensky
• University of California, Irvine
• C. Chen, M. Hebert, P. Huwe,
• W. Molzon, J. Popp, V. Tumakov
• University of Houston
• Y. Cui, N. Elkhayari, E. V. Hungerford,
• N. Klantarians, K. A. Lan

University of Massachusetts, Amherst K.
Kumar Institute for Nuclear Research, Moscow V.
M. Lobashev, V. Matushko New
York University R. M. Djilkibaev, A. Mincer,
P. Nemethy, J. Sculli Osaka
University M. Aoki, Y. Kuno, A. Sato University
of Virginia C. Dukes, K. Nelson, A.
Norman Syracuse University R. Holmes, P.
Souder College of William and Mary M. Eckhause,
J. Kane, R. Welsh
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We want to measure R?e with Sensitivity
Need

• High Proton Flux, High Muon Collection
  Efficiency, goal 1011muon stops/sec
• High Background Rejection, High Extinction

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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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MECO Requirements

• Increase the muon flux (graded solenoid, MELC
  design), collect 10-2 muons/proton
• Use pulsed beam with for prompt background rejection
• Detect only promising events defines
  detector geometry resolution requirements
• Use cosmic ray veto

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Number of p- per InteractionComparison with Data
Pions/GeV
By V. Tumakov
Prediction for MECO Beam
GHEISHA DATA GCALOR FLUKA
Kinetic Energy GeV
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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
Proton Beam
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Charged particles helix conserves flux

• R2?B is constant
• i.e. in a graded solenoid transverse momentum
  is transformed into longitudinal increasing its
  collection efficiency.

is constant too,
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Magnetic Field Overview
Production region
Magnetic field vs distance
5T
Curved sections
Curved sections
Detector region

• Curved sections

3T
1T
At 3.3 Tesla 75 of muon capture efficiency of 5
Tesla.
0
10
20
Distance along beam path m
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Muon Beam Transport with Curved Solenoid

• Goals
• Transport low energy ?-to the detector solenoid
• Minimize transport of positive particles and
  high energy particles
• Minimize transport of neutral particles
• Absorb anti-protons in a thin window
• Minimize long transittime trajectories

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Sign and Momentum Selection in the Curved
Transport Solenoid
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Momentum and Time Distributions in MECO Muon Beam
Relative Flux
Particles/proton/ns
e- e m- m
e-
e
m-
m
Time ns
Momentum MeV/c
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Transported and stopped muons
Transported muon spectrum
Stopped muon spectrum
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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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Expected Sensitivity of the MECO Experiment

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

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MECO at Brookhaven National Laboratory
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Extinction at the AGS of BNL

• Extinction of 10-9

Use 6 buckets, only two of them filled with beam.
Time between filled buckets 1.35 ?s
Measurement Time
AGS Ring
20TP
20TP
Extinction of 10-9
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RSVP/MECO Milestones
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MECO Cost Estimates

• Solenoids 57M
• Meco Experimental Equipment 26M