Philip HarrisUniversity of Sussex(for the EDM Collaboration)

The Neutron EDM Experimentsat the ILL

P. Harris

University of Sussex

Highlights

New (but preliminary) limit: |dn| < 3.1 x 10-26 e.cm

1. nEDM “Classic”

2. CryoEDMUnder development:

100x improved sensitivity

P. Harris

University of Sussex

Electric Dipole Moments

Separation between+,- charge centres

EDMs are P odd T odd

Complementary approachto study of CPv

E +

dn = dn s

P. Harris

University of Sussex

SM EDM predictions very small... ... so no SM background to worry about

Beyond SM predictions typ. 106

greater ... so EDMs are excellent probe of BSM

CPv SM parameterisation of CPv

inadequate to explain baryon asymmetry

Strong CP Problem: s < 10-10 rads

CP violation & the neutron EDM

P. Harris

University of Sussex

dq, dq ~ (loop factor) sin CP c

2

mq

Implications for SUSY

quark electric dipole moments

q q

gaugino

squark

quark color dipole moments

q q

g

gaugino

squark

CP phase from soft breaking naturally O(1)

scale of SUSY breaking naturally ~200 GeV

naturally ~

du,d, du,d ~ 31024 cm naturallyc

n and Hg experiments give du< 2 1025

dd< 5 1026

du< 3 1026

dd< 3 1026

c

c

~ 100 times less! > 2 TeV ? CP < 10-2 ?

P. Harris

University of Sussex

History

Factor 10every 8 yearson average

Now

CryoEDM

P. Harris

University of Sussex

Measurement principle

() – () = – 4 E d/ h

assuming B unchanged when E is reversed.

B0 E<Sz> = + h/2

<Sz> = - h/2

h(0) h() h()

B0 B0 E

Energy resolution of our detector:10-21 eV

Use NMR on ultracold neutrons in B, E fields.

P. Harris

University of Sussex

Apparatus

Neutronstoragechamber

HVfeedthru

B-fieldcoils

P. Harris

University of Sussex0 5 10 15 20 25

29.9260

29.9265

29.9270

29.9275

29.9280

29.9285

29.9290

29.9295

Neu

tron

res

onan

t fr

eque

ncy

(Hz)

Run duration (hours)

nEDM measurement Look for n freq changes correlated with changes in E

Electric Field

+-

P. Harris

University of Sussex0 5 10 15 20

7.7882

7.7884

7.7886

7.7888

7.7890

Run duration (hours)

Mer

cury

freq

uenc

y (H

z)

Mercury co-magnetometer

Compensates B drift...

P. Harris

University of Sussex0 5 10 15 20 25

29.9260

29.9265

29.9270

29.9275

29.9280

29.9285

29.9290

B = 10 -10 T

Raw neutron frequencyCorrected frequency

Pre

cess

ion

freq

uenc

y (H

z)

Run duration (hours)

nEDM measurement

29.9295

P. Harris

University of Sussex

Neutron EDM results (binned)

-10

-8

-6

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-2

0

2

4

6

8

10

500 700 900 1100 1300 1500 1700 1900 2100

ED

M (

10-2

5 e.c

m)

Current limitset here

Stat. limit now 1.54 x 10-26 e.cm

P. Harris

University of Sussex

Systematics Consider

Should have value 1 R is shifted by magnetic field

gradients Plot EDM vs measured R-1:

n

Hg

Hg

nR

P. Harris

University of Sussex

Systematics

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-50

0

50

100

150

-40 -20 0 20 40

R-1 (ppm)

ED

M (

10-2

5 e.c

m)

Magnetic field down

z

B

P. Harris

University of Sussex

Systematics

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-50

0

50

100

150

-10 0 10 20 30 40

R-1 (ppm)

ED

M (

10

-26 e

.cm

)

Magnetic field up

z

B

P. Harris

University of Sussex

Geometric phase

rBz

Br

and, from Special Relativity, extra motion-induced field

2

1

c

EvB

Two effects:

J.M. Pendlebury et al., PRA 70 032102 (2004)

P. Harris

University of Sussex

Geometric phase

Br

Br

Bnet

Bnet

Bv

Bv

Bv

Bnet

Bnet

... so particlesees additionalrotating field

Frequency shift E

Looks likean EDM

Bottle(top view)

P. Harris

University of Sussex

Results

R-1

EDM

0

B down

B up The answer?

Nearly...

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0

50

100

150

-40 -20 0 20 40

R-1 (ppm)

ED

M (1

0-2

5 e

.cm

)

-150

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-50

0

50

100

150

-10 0 10 20 30 40

R-1 (ppm)

EDM

(10

-26

e.c

m)

P. Harris

University of Sussex

Results

R-1

EDM

0

Small dipole/quadrupole fields can pull lines apart

& add GP shiftsB up

B down

P. Harris

University of Sussex

Results

R-1

EDM

0

Small dipole/quadrupole fields can pull lines apart

& add GP shiftsB up

B down

Measure and apply correction

...difficult!

P. Harris

University of Sussex

Error budgetStatistical 1.54E-26 e.cm

Dipole & quadrupole shifts 6E-27 e.cm

Enhanced GP dipole shifts ~4E-27 e.cm

(E x v)/c2 from translation 1E-27 e.cm

(E x v)/c2 from rotation 1E-27 e.cm

Light shift: direct 8E-28 e.cm

B fluctuations 7E-28 e.cm

E forces – distortion of bottle

4E-28 e.cm

Tangential leakage currents

1E-28 e.cm

AC B fields from HV ripple <1E-28 e.cm

Light shift: GP effects 8E-28 e.cm

P. Harris

University of Sussex

PRELIMINARY Results

New (preliminary) limit:|dn| < 3.1 x 10-26 e.cm (90% CL)

dn = (-0.31 1.54 1.00) x 10-26 e.cm

Preprint expected soon

P. Harris

University of Sussex

CryoEDM

100-fold improvement in sensitivity!

n = 8.9 Å; E = 1.03 meV

Landau-Feynman dispersion curve for 4He excitations

Dispersion curve for free neutrons

R. Golub and J.M. Pendlebury Phys. Lett. 53A (1975), Phys. Lett. 62A (1977)

•More neutrons•Higher E field•Better polarisation•Better NMR time

P. Harris

University of Sussex

CryoEDM overviewNeutron beam input

Transfer section

Cryogenic Ramsey chamber

P. Harris

University of Sussex

Cryogenic Ramsey chamber

Superfluid He

HV electrode

n storage cells

P. Harris

University of Sussex

CryoEDM

Turns onOctober 2006

P. Harris

University of Sussex

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0

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R-1 (ppm)

EDM

(10

-26

e.c

m)

Conclusions

EDM “Classic”: new (preliminary) limit, factor 2 improvement

CryoEDM coming soon – 100x more sensitive

Watch this space!

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R-1 (ppm)

ED

M (

10-2

5 e

.cm

)

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0

2

4

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8

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500 700 900 1100 1300 1500 1700 1900 2100

ED

M (

10-2

5 e.c

m)