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