Yannis K. SemertzidisBrookhaven National Laboratory

MSI-05 KEK, 1-4 March 2005

•LFV: Physics Reach•LFV Experimental Techniques•MECO Experiment at BNL•Intensity, Collection Efficiency•Extinction Issues

Large Acceptance and High Extinction Pion/Muon Beamline for the MECO

Experiment at BNL

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

Three Generations…leptons quarks

G=1 e e u dG=2 c sG=3 t b

Lepton Number isConserved…

MECO is searching forthe COHERENTconversion of ein the field of anucleus (Al, Ti).

2

2

2W

mM

Rate

Neutrino Oscillations:

Y. Okada: “Large effectsare expected in wellmotivated SUSY models”

Supersymmetry Predictions for e Conversion

Process Current 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

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 = m c2 – Ebinding – Erecoil

= 105.6 – 0.25 – 0.25 MeV

ee

NeN

We want to measure Re with Sensitivity:

• High Proton Flux, High Muon Collection Efficiency, goal: ~1011muon stops/sec

• High Background Rejection, High Extinction

17102)1,(),(

ZNZNNeNR e

Need

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), collect ~10-2 muons/proton

• Use pulsed beam with <10-9 extinction in between for prompt background rejection

• Detect …only promising events defines detector geometry; resolution requirements

• Use cosmic ray veto

Number of - per InteractionComparison with Data…

GHEISHADATAGCALORFLUKA

Kinetic Energy [GeV]

Pio

ns/G

eV

Prediction for MECO Beam By V. Tumakov

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

Proton Beam

Charged particle’s helix conserves flux…

R2B is constant

i.e. in a graded solenoid transverse momentum is transformed into longitudinal increasing its collection efficiency.

BPT

2

is constant too,

Magnetic Field Overview

•Curved sections

Curved sections

Detector region

Curved sections

Production region

5T

3T

1T

Distance along beam path [m]100 20

Magnetic field vs distance

At 3.3 Tesla: 75% of muon capture efficiency of 5 Tesla.

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

Muon Beam Transport with Curved Solenoid

2.5T

2.4T

2.1T

2.1T 2.0T

2.4T

Sign and Momentum Selection in the Curved Transport Solenoid

2 2s t

s

1+ p2p1 sD= × × p0.3B R

e-

-

e+

+

Time [ns]

Momentum and Time Distributions in MECO Muon BeamR

elat

ive

Flux

Momentum [MeV/c]

e-

e+

Part

icle

s/pr

oton

/ns

Transported and stopped muons

Transported muonspectrum

Stopped muonspectrum

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

Two Tracking Detector option are being considered

–Longitudinal geometry with ~3000 3m long straws–Transverse geometry with ~13000 1.4 m straws Both geometries appear to meet physics requirements

Longitudinal Tracker

Spectrometer Performance Calculations

FWHM ~900 keV

10

1.0

0.1

0.01 103 104 105 106

Aiming for ~200 KeV resolution

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 FactorRunning 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 0.60Fraction of capture in detection time window 0.49Electron trigger efficiency 0.90Fitting and selection criteria efficiency 0.19Detected 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; resolution

Tracking errors < 0.006Radiative decay < 0.005Beam e- < 0.04 decay in flight < 0.03 Without scattering in stopping target

decay in flight 0.04 With scattering in stopping targetdecay in flight < 0.001Radiative capture 0.07 From out of time protons; extinctionRadiative capture 0.001 From late arriving pionsAnti-proton induced 0.007 Mostly from

Cosmic ray induced 0.004 Assuming 10-4 CR veto inefficiencyTotal Background 0.45 Assuming 10-9 inter-bunch extinction

Required Extinction vs Time

MECO at Brookhaven National Laboratory

•Extinction of 10-9

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)

Mike Brennan (1998)

s

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

magnetic

kick

AC magnet

Buckets at AGS with h=6, W. Glenn

Buckets are connected creating unstable fixed points.

One or Two filled buckets? (W.Glenn)• At Injection the proton phase space is large

(scales as 1/). While waiting for the second injection (~0.2s) protons hop into the next buckets…

-1

-0.5

0

0.5

1

-3.14 -1.57 0 1.57 3.14

phi

d ph

i/dt

coasting

max dB/dt

,x

,y

In :

In :

x n

y n

xx

yy

Coasting bucket

Accelerated bucket

Preventing Bucket Contamination:

We are planning

• To study the one vs two filled buckets in the AGS ring with simulation and beam.

• Measure extinction in the AGS to 10-9

• Use external monitor and use an external extinction device as “insurance”.

RSVP/MECO Milestones

Milestone

Cost Baseline April `05HEPAP review 2005$15M for FY2005 for RSVP, available after baseline/HEPAP review decisionsPresident’s request for RSVP for FY2006 $42M

Start data taking 2011