Measuring the Neutron Electric
Dipole Moment - A Tiny Number
with Big Implications
Dave Wark
Imperial/RAL
Kyoto University
Nov. 2nd, 2005

The Universe passed througha period of the very highenergy density early in the
Big Bang
Matter was produced via–
reactions like γ+γ→p+p

tion

This should have produced
equal quantities of matter andanti-matter.
…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

It didn’t….

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

d0 = 20 Mpc

tion

d0 = 1000 Mpc…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2
Diffuse γ-ray flux expected from annihilation’05

See Cohen, De Rujula, Glashow; astro-ph/9707087
Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violationtion¾ C violation…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violationtion¾ C and CP violation…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

CP violation in weak decays

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05…CP violation

K0L →2π

Dave Wark
Imperial College/RAL

CP violation in weak decays…CP viola

BELLE and BaBartion

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

CPLear (amongst others)

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violationtion¾ C and CP violation…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violationtion¾ C and CP violation ;…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violation¾ Departure from thermal equilibriumtion¾ C and CP violation ;…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violation¾ Departure from thermal equilibrium; Phase transitionstion¾ C and CP violation ;…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Sakharov Conditions:(A.D. Sakharov, JETP Lett. 5, 24-27, 1967)• To produce a matter ↔ anti-matterasymmetry requires:¾ Baryon number violation: Conserved at tree level in the Standard Model; More complex SM processes lead to B violation¾ Departure from thermal equilibrium; Phase transitions; Expansion of the Universetion¾ C and CP violation ;…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

So are we done now?

tion

• No (you don’t get out of this talk that easy)• The CP violation in the Standard Model is
too small by many orders of magnitude to
explain the observed matter-anti-matterasymmetry (also called the baryon
asymmetry) of the Universe (hep-ph/0303065)• There must be CPV in laws of physics wedon’t know yet!
• We have to keep looking…

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Electric Dipole Moment…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Electric Dipole Moment…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Electric Dipole Moment
+

tion

_

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Electric Dipole Moment
+

⇀s

tion

_

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Electric Dipole Moment+⇀s

Would lead to a non-zero value for ⇀dn,either parallel or anti-parallel to ⇀sd⇀ would be:
n

P odd
T odd
CP odd!

tion_…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL• Particle EDMs are a particularly promisinglaboratory for CP violation

tion– The Standard Model contribution is very small– Contributions from new physics tend not to be…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

10-20
10-22
10-24
10-26
10-28
10-30
neutronStandard Model…CP viol
a

10-34

tion

10-32

Range of d (e cm) in various models

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Rightφ ∼ α/π10-30
neutron

10-34

tion

10-32

Standard Model…CP viola

10-20

Range of d (e cm) in various models

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

Basic Idea of the Measurement

B

tion

µB

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Basic Idea of the Measurement

E
µB

dn ??

tion

B

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Basic Idea of the Measurement

E
µB

dn ??

Look for a shift in the Larmor
frequency of 2·E·dn as E is flipped
relative to B

tion

B

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

1.

“Spin up”
neutron...

2.

Apply π/2
spin
flip pulse...

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

The Ramsey
Separated
Oscillator
MethodFree
precession...

N.F. Ramsey,
Phys.Rev.76
996 (1949)

4.

Second π/2
spin
flip pulse.

…CP viol
a

tion

3.

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

λ>> interatomic spacing; neutrons see Fermi
potential VF
Critical velocity for reflection:½mvc2 = VF
Ultracold neutrons (UCN): v ∼ 6 m/s: totalinternal reflection possible.

tion

n

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

λ>> interatomic spacing; neutrons see Fermi
potential VF
Critical velocity for reflection:½mvc2 = VF
Ultracold neutrons (UCN): v ∼ 6 m/s: totalinternal reflection possible.
ntion

vc depends on orientation of neutron spin, so canpolarise by transmission.
…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

λ>> interatomic spacing; neutrons see Fermi
potential VF
Critical velocity for reflection:½mvc2 = VF
Ultracold neutrons (UCN): v ∼ 6 m/s: totalinternal reflection possible.

vc depends on orientation of neutron spin, so canpolarise by transmission.
n
s
B
s

n

tion

n

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

( N 1↑↑ − N 2↑↑ − N 1↑↓+ N 2↑↓ )h
dn =
2αETN
Where α = the product of the neutron polarisation and theanalyzing power, E is the applied field strength, T is thestorage time, and N is the number of neutrons detectedhσ (d n ) =2αET N
Must add any systematics to this to determine thesensitivity of the experiment.

tion

The resulting “statistical” sensitivity is:…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2
Prepare neutrons in polarisation state 1, execute Ramsey’05
cycle and measure the number left in states 1 and 2, repeat
with B and E fields parallel (↑↑) and anti-parallel (↑↓), then:Dave Wark
Imperial College/RAL

The Institute Laue-Langevin…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Turbine

Reactor Core
Liquid D2 moderator

tion

Vertical guide…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Neutron Energy Annoyances• “Cold” neutrons have:– E ≈ 0.1 – 1 meV– v ≈ 100 m/s− λ ≈ 1-10 Å– T ≈ 10 K
– E ≈ 1 – 10 neV– v ≈ 0-15 m/s− λ ≈ 1000 Å– T ≈ real small (normally not thermal)tion• “Ultra-cold” neutrons have:…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Four-layer mu-metal shield

High voltage lead

Quartz insulating
cylinderCoil for 10 mG
magnetic fieldUpperelectrode

Main storagecell
Hg u.v.
lamp

PMT todetect Hg
u.v. light

Vacuum wall

Hg u.v. lamp
S

N

UCN guidechangeovertion

Current RoomRF coil to flip spins
Temperature
MagnetnEDM
Experiment UCN polarising foil

Mercury
prepolarisingcell

Ultracold
neutrons(UCN)…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

UCN detector

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Wark
DaveImperial
ImperialCollege/RAL
College/RAL

Four-layer mu-metal shield

High voltage lead

Quartz insulating
cylinderCoil for 10 mG
magnetic fieldUpperelectrode

Main storagecell
Hg u.v.
lamp

PMT todetect Hg
u.v. light

Vacuum wall

Hg u.v. lamp
S

N

UCN guidechangeovertion

Current RoomRF coil to flip spins
Temperature
MagnetnEDM
Experiment UCN polarising foil

Mercury
prepolarisingcell

Ultracold
neutrons(UCN)…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

UCN detector

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2Top view:’05
DM and…

Hg
Co-magnetometer

Neutro
nE

PMT

30000

T'

10000
0

tion

-1 0 0 0 0-2 0 0 0 0…CP viola

Digitised voltage (bits)

20000-3 0 0 0 0-4 0 0 0 0-5 0 0 0 0
0

2000

4000

6000

8000

A D C re a d in g n o .

10000

12000

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

1999 Results(PG Harris et al, PRL 82, 904 (1999))…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

dn = (1.9 ± 5.4)×10−26 e cm ⇒dn ≤ 6.3 ×10−26 e cm (90% c.l.)Dave Wark
Imperial College/RAL

If neutron were the size of the earth...

∆x-e... current EDM limit
would correspond to charge
separation of ∆x ≈ 10 µ.

…CP viol
a

+e

tion

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Rightφ ∼ α/π10-30
neutron

10-34

tion

10-32

Standard Model…CP viola

10-20

Range of d (e cm) in various models

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

neutron:

10-20

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Right10-30

φ ∼ α/π10-301960 1970 1980 1990 2000

neutronCited ~250 times already

10-34

tion

10-32

Standard Model…CP viola

10-20

Range of d (e cm) in various models

Experimental Limit on d (e cm)

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05
NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N
Published
Data

Current
Room-Temp

Cryogenic
Experimentα…CP viol
a

T

tion

E

N
Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2
’05

α

0.5

E

4.5 kV/cm

T

130 s

N

13000

Current
Room-Temp

Cryogenic
Experimenttion

PublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

New polarisers
E
on Si wafers
T
N

Current
Room-Temp

0.5

0.7

Cryogenic
Experiment

4.5 kV/cm
130 s

tion

α

PublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

13000
Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

E

Current
Room-Temp

0.5

0.7

Cryogenic
Experiment

4.5 kV/cm 12 kV/cm

T bottle130 s
Shorter, wider
4He buffer gas
Better cleaning
N methods
13000

tion

α

PublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

E

Current
Room-Temp

0.5

0.7

Cryogenic
Experiment

4.5 kV/cm 12 kV/cm

T

130 s

N

13000

130 s

tion

α

PublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05
NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N
Published
Data

Current
Room-Temp

Cryogenic
Experiment

130 s

130 s

N

13000

14000

…CP viol
a

T

tion

Larger volume
α bottle0.5
0.7
Better neutron guides
Loss of 50% from sourceE
4.5 kV/cm 12 kV/cm

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

E

Current
Room-Temp

0.5

0.7

Cryogenic
Experiment

4.5 kV/cm 12 kV/cm

T

130 s

130 s

N

13000

14000

tion

α

PublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

E

Current
Room-Temp

0.5

0.7

Cryogenic
Experiment

4.5 kV/cm 12 kV/cm

T

130 s

130 s

N

13000

14000

tion

α

PublishedData…CP viola

NeutronE

DM and…

Overall factor of ~3 improvement

Dave Wark
Imperial College/RAL

1999 Results(PG Harris et al, PRL 82, 904 (1999))

DM and…

Kyoto Seminar
Nov. 2’05
NeutronE

101999 limit
set here

8
6

2
0
500
-2

700

900

1100

1300

1500

1700

1900

2100

-6
-8

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

-10

tion

-4

…CP viola

EDM (10-25 e.cm)

4dn = (1.9 ± 5.4)×10−26 e cm ⇒dn ≤ 6.3 ×10−26 e cm (90% c.l.)Dave Wark
Wark
DaveImperial
ImperialCollege/RAL
College/RAL

-40

tion

-30

1

698

681

664

647

630

613

596

579

562

545

528

511

494

477

460

443

426

409

392

375

358

341

324

307

290

273

256

239

222

205

188

171

154

137

120

103

86

69

52

35

18

e.cm)

DM and…

50

What’s going on here?

…CP viola-25

EDM (10

NeutronE

Kyoto Seminar
Nov. 2’05

New nEDM data

χ2/ν = 1.13; CL = 0.7%! Smells fishy...

40

30

20

10

0

-10

-20

-50

Dave Wark
Imperial College/RAL

Conspiracy Theorytion

Two effects:∂B⇒ Br ∝ r∂z

and, from Special Relativity, extra
r motion-induced field

r
1 v×E
B′ =
γ c2

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Geometric Phase
Bnet
Bv

Bv

... so particle
sees additionalrotating field
Frequency shift∝E
Looks likean EDM

Bnet

tion

Br

…CP viola

Bnet

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

Bv
Br

Bnet

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05•Verified in data: Measured EDM depends upon appliedmagnetic field gradient, with exactly predicted dependence•Mercury magnetometer now provides our largest systematic!
•More precise field measurements will allow us tocompensate this effect to ~4x10-27 e.cm

NeutronE

DM and…

Field Gradient Effect

Magnetic Field Down

Magnetic Field Up

30

25

20

15

10

10

5

-12

-7

-2

3

8

13

0
-12

-10

-10

-8

-6

-4

-2

0

-5

-10

2

4

6

tion

0
8

…CP viola

False ED M (1E-25 e.cm )

20

-20
-15

-30

dB/dz (nT/m)-20

dB/dz (nT/m)

Dave Wark
Imperial College/RAL

Statistical
Dipole & quadrupole shifts
Enhanced GP dipole shifts(E x v)/c2 from translation(E x v)/c2 from rotation
Light shift: direct
B fluctuations
E forces – distortion of bottle
Tangential leakage currents
AC B fields from HV ripple
Light shift: GP effects

1.54E-26 e.cm
6E-27 e.cm
4E-27 e.cm
1E-27 e.cm
1E-27 e.cm
8E-28 e.cm
7E-28 e.cm
4E-28 e.cm
1E-28 e.cm
<1E-28 e.cm
includedtion

Error Budget for Total Data Set…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

at SUSY05 (preliminary)

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

Preprint expected soontion

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

NeutronE

DM and…

Kyoto Seminar
Nov. 2
My colleagues announced new results’05

Dave Wark
Imperial College/RAL

How will we do better?

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL• Existing limits are already a challenge fortheorists – for instance, the strong
interaction CP phase θs must be ≤ 10-10• Many other models are also challenged, forinstance the “natural” scale for nEDM
caused by CP violation in SUSY models is
10-23 to 10-24 e cm.
• We have therefore already learned
something significant about SUSY – if
SUSY exists, there is some structure to thetheory to suppress CP violation.

tion

Do we want to do better?

…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Do we want to do better?

• If we can push our sensitivity to ~ 10-28 e cm, theneither:• If SUSY does not exist, we still must explain thebaryon asymmetry so investigations sensitive to
new sources of CP violation are critical.

tion– We will observe an nEDM
– SUSY is not a property of nature (see below)– CP violation is an approximate symmetry of nature– CP violation has an off-diagonal structure, or there arelarge cancellations, or some as-of-yet unknown othermechanism strongly suppresses EDMs
…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL• University of Sussex - K. Green, M.G.D. van der
Grinten, P.G.Harris, J.M.Pendlebury, D.B.Shiers,
K.Zuber• RAL - S.N.Balashov, M.A.H.Tucker, D.L.Wark• University of Oxford - H.Kraus, S. Henry• Kure University – H. Yoshiki• Visiting Scientists – P. Iaydjiev and S. Ivanov.

tion

Cryogenic nEDM Collaboration…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

11 K; 2π/k = 8.9 Å

Landau-Feynman
dispersion curve for 4He
excitations

tion

Dispersion curve forfree neutrons…CP viola• Need a new source of UCN….

Golub and Pendlebury, Phys. Lett. A53 133(1975)

How will we do better?

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05• To use this we need….
Dave Wark
Imperial College/RAL

11 K; 2π/k = 8.9 Å

Landau-Feynman
dispersion curve for 4He
excitations

tion

Dispersion curve forfree neutrons…CP viola• Need a new source of UCN….

Golub and Pendlebury, Phys. Lett. A53 133(1975)

How will we do better?

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05• To use this we need….
Dave Wark
Imperial College/RAL

Entire Cryostat and pumps provided
by Hajime Yoshiki from Kure

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Next Generation Experiment…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Wark
DaveImperial
ImperialCollege/RAL
College/RAL

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Detectors that will work in 0.5K
LHe…

Development funded by PPARC
Blue Skies Detector Fund
ORTEC ULTRA silicon detectors
Coated with a thin layer of 6LiF

F

14
13
12
11
10
9
8

7%

7
6

They work, although the efficiency
could be further improved by lowering noise

tion

5
4
3
2
1
0

0

100

200

300

400

500

600

700

800

900

1000

C hannel…CP violaCounts/sec

Observe n+6Li→α+t

See C.A.Baker et al., NIM A487 511-520 (2002)
Dave Wark
Imperial College/RAL

Must demonstrate that the production
mechanism really works…

1.19±0.18 UCN cm-3 s-1
expected, 0.91± 0.13 observed
See C.A.Baker et al., Phys.Lett. A308 67-74 (2002)tion

A velocity-selected beamof cold neutrons passes
through LHe, the UCN
are bottled and detected…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Show that polarisation is retained
during downscattering…
Inferredpolarisation

Polariser aligned
Polariser anti-aligned

UCN polarisation is(0.93 ± 0.10) of thepolarisation of theincoming beamtion

No Fe polariser…CP viola

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

SCV

Ramsey Cell

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

– Developed at Oxford for
CRESST– Sensitivity sufficient tomonitor field– Measure field coupling aloop rather than volume
average, therefore needquite a few

tion• SQUID Magnetometers…CP viola

DM andAll New Magnetometry System

NeutronE…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

– Developed at Oxford for
CRESST– Sensitivity sufficient tomonitor field– Measure field coupling aloop rather than volume
average, therefore needquite a few• Neutron Magnetometerstion• SQUID Magnetometers…CP viola

DM andAll New Magnetometry System

NeutronE…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Ramsey Cell and SF Vessel…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Wark
DaveImperial
ImperialCollege/RAL
College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05

E

Current
Room-Temp

Cryogenic
Experiment

0.5

0.7

0.9

4.5 kV/cm 12 kV/cm 40 kV/cm

T

130 s

130 s

300 s

N

13000

14000

700000tion

αPublishedData…CP viola

NeutronE

DM and…

h
Recall: σ ( d n ) =2αET N

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05 • A group at KEK/Osaka is building an experiment to be

•

•
•
•
•

tion

•

used at JPARC
A group at PSI based around the group from PNPI areproceeding with an experiment.
A very large American collaboration is proposing anexperiment at the SNS – their proposal lists 36 names,
requests $11M, with a target date for first data of 2007.
There is a German group at the new reactor in Munich.
There are also experiments to measure the eEDM, atomic
EDMs, and even the muon EDM.
Competition is good, but uncomfortable when you are thetarget of it!
However any observation would need to be confirmed
extended, so many experiments are needed.

…CP viola

NeutronE

DM and…

The Competition…

Dave Wark
Imperial College/RAL

Kyoto Seminar
Nov. 2’05 • Strong evidence exists from astrophysicaltionmeasurements that CP violation exists in some asof-yet undiscovered properties of fundamental
interactions.
• Particle EDMs offer a sensitive probe of such newphysics (at very modest cost) – the final nEDM
limit from the existing experiment extends thesensitivity by another factor of 2.
• We have not yet reached any fundamental limits toincreased sensitivity.
• The Japanese have made a very significant
contribution to our new cryogenic experiment, andare welcome to help exploit it.
• Other EDM experiments are just as important. Dave Wark

…CP viola

NeutronE

DM and…

Conclusions…

Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

neutron:

10-20

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Right

10-30
1960 1970 1980 1990 2000

neutron

10-32
10-34

tion

10-30

φ ∼ α/πStandard Model…CP viola

10-20

Range of d (e cm) in various models

Experimental Limit on d (e cm)

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

…CP violation

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL

neutron:

10-20

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Right

10-30
1960 1970 1980 1990 2000

neutron

10-32
10-34

tion

10-30

φ ∼ α/πStandard Model…CP viola

10-20

Range of d (e cm) in various models

Experimental Limit on d (e cm)

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

neutron:electron:

10-20

Electromagnetic

10-22
10-24
Multi
Higgs

SUSY
φ∼1

Left-Right

10-30
1960 1970 1980 1990 2000

neutron

10-32
10-34

tion

10-30

φ ∼ α/πStandard Model…CP viola

10-20

Range of d (e cm) in various models

Experimental Limit on d (e cm)

NeutronE

DM and…

Kyoto Seminar
Nov. 2
’05

10-36
10-38

electronDave Wark
Imperial College/RAL

199Hg Electric Dipole Moment
hep-ex/0012001

DM and…

Kyoto Seminar
Nov. 2’05
NeutronE• Optically pumped 199Hg
atoms precess in B,
E fields, modulating
absorption signal

Result:d(199Hg) < 2.1 x 10-28 e cm

…CP violaDual cells remove
effect of drifts in B
tion






Provides good limit on CPv effects in nuclear forces, inc. θQCD
If from valence neutron, corresponds to dn<2x10-25 ecm, because ofelectrostatic shielding.
Dave Wark

Imperial College/RAL

neutron:electron:

10-20

Electromagnetic

10-22
10-24
Multi
Higgs

199Hg atomic EDM

10-30

•

SUSY
φ∼1

Left-Rightφ ∼ α/π10-301960 1970 1980 1990 2000

neutronRelative value of neutron,
10-34
electron, atomic (and µ and τ)
10-36
EDM is modeldependent, must pursue all 10-38

tion

10-32

Standard Modelelectron…CP viola

10-20

Range of d (e cm) in various models

Experimental Limit on d (e cm)

NeutronE

DM and…

Kyoto Seminar
Nov. 2’05

Dave Wark
Imperial College/RAL