Electric dipole moments: theory and experiment

EA Hinds

Blois June 2002

Two motivations to measure EDMs

EDM is effectively zero in standard modelbut

big enough to measure in non-standard models

direct test of physics beyond the standard model

EDM violates T symmetry

Deeply connected to CP violation and the matter-antimatter asymmetry of the universe

φ ∼ 1

Left-Right

10-32

10-20

10-22

10-24

10-30

MultiHiggs SUSY

φ ∼ α/π

Standard Model

Electro-magnetic

10-34

10-36

10-38

Exp

erim

enta

l Lim

it on

d (

e.cm

)

1960 1970 1980 1990

neutron:electron:

2000

10-20

10-30

10-22

10-24

10-26

10-28

A bit of history

thallium

atom/moleculelevel

CP from particles to atoms (main connections)

nuclearlevel

NNNNSchiff

momentmercury

HiggsSUSY

Left/Right

StrongCP

field theoryCP model

θGG%

neutron

nucleonlevel

electron/quarklevel

de

dq

dcq

The Mercury EDM experimentUniversity of Washington, Seattle

M.V. Romalis, W.C. Griffith, J.P. Jacobs, E.N. Fortson

Nuclear spin polarised 199Hg vapor in a double cell

hω = µB

+ dEE

- dE±

B

ω± measured optically

199

Hg

ED

M (1

0-27

e.cm

)

GSI992

Hg edm result: Phys. Rev. Lett. 86, 2505 (2001)

|dHg| < 2.1×10-28 e cm

E = 9 kV/cm

B = 15 µT stable to 0.4 pT

Tcoherence ~ 100 s

Difference of precession frequencies gives 199Hg EDM

The Neutron EDM

Rutherford-Appleton LaboratoryCA Baker, K Green, P Iaydjiev, S Ivanov

Sussex UniversityS Al-Ayoubi, PG Harris, JM Pendlebury, JD Richardson, D Shiers, K F Smith, M van der Grinten

ILLP Geltenbort

• Ultracold neutrons in a bottleprecess at frequency (µnB ± dnE)/h

• Reverse E to measure dn

GSI992

Neutron edm result: Phys. Rev. Lett. 82, 904 (1999)

|dn|< 6.3×10-26 e cm

E = 4.5 kV/cm

B = 1 µT

Tcoherence ~ 130 s

Hg co-magnetometer

(B is measured to 1 pT rms)

Aiming at 10-27 e.cm over next decade

Neutron: longer range plans

§ Helium (ILL, LANL)Inside the heliumHigher neutron densityHigher E field

New moderators using liquid helium or solid deuterium

§ Deuterium (PSI, TU-Munich)Outside the deuteriumHigher neutron densityBigger volume (fast moderation)

Implications of n and Hg for the theta parameter

θ gs2

32π2GG~

CP strong interaction

dn» 10-16 θ

\ θ < 6×10-10n n

γ

p

π −

×

induces neutron EDMBaluniCrewtherPospelov

Henley & HaxtonPospelov

induces mercury Schiff moment

N/

π ×N

dHg» 3 10-19

θ

\ θ < 6×10-10

Something(Peccei-Quinn?)

makes θ very small!

Implications of Hg and nfor SUSY

quark electric dipole moments

dq q (Fµν σµνiγ5 ) q21

q q

γ

gaugino

squark

quark color dipole moments

q q

g

gaugino

squark

dq q (gs Gµνσµνiγ5 ) q21 c

2Λmqdq, dq ~ (loop factor) × sin ϕCP

cCP phase from soft breaking

naturally O(1)

scale of SUSY breaking naturally ~200 GeV

naturally ~ α/π

du,d, du,d ~ 1×10−23 cm naturallyc

n and Hg experiments give du< 2 × 10−25

dd< 5 × 10−26

du< 3 × 10−26

dd< 3 × 10−26

c

c

~ 300 times less!

ϕCP < 3×10-3 ??

Λ > 5 TeV ??

thallium

atom/moleculelevel

CP from particles to atoms (main connections)

nuclearlevel

NNNNSchiff

momentmercury

HiggsSUSY

Left/Right

StrongCP

field theoryCP model

θGG%

neutron

nucleonlevel

electron/quarklevel

de

dq

dcq

And now for the electron………..

The Thallium EDM experimentBerkeley B.C. Regan, E.D. Commins, C.J. Schmidt and D. DeMille

2 Tl atomic beams

hω = µB

polarise

analyse

± dEE±B

The solution:add 2 more Tl beams going down

4

analyse

polarise

The solution:Add 4 Na beams for magnetometry

1st huge problem:motional interaction µ • v × E

2nd huge problem:stray static magnetic fields

A beautiful feature of the method

E

electric field

Interaction energy

-de ηE•σ

ηde σ

atom containing electron

amplification

-585 for Tl

(Sandars)

Effective field = 72 MV/cm× 585

÷ 585electron edm result:

|de|< 1.6 ×10-27 e.cm

E = 123 kV/cm

B = 38 µT

Tcoherence = 2.4 ms

Na co-magnetometer

Final Tl result: PRL 88, 071805 (2002)

|dTl|< 9.4 ×10-25 e.cm

Theoretical consequences of electron EDM

SUSY electron edm

e e

γselectron2Λ

mede ~ (loop) × sin ϕCP

No direct contamination from θ problem

- a pure new physics search

~ 5 × 10−24 cm

Once again, natural SUSY is too big by 300

ϕCP < 3×10-3 ?? Λ > 5 TeV ??

potentially 1000 × more sensitive

The Sussex experiment uses ytterbium fluoride moleculesJJ Hudson, BE Sauer, MR Tarbutt and EA Hinds,

arXiv hep-ex0202014 (2002)

The future for electron EDM experiments

polar molecules

0

5

10

15

20

0 10 20 30

Applied field E (kV/cm)

Effe

ctiv

e fie

ld η

E (G

V/c

m)

(in Tl experiment ηΕ was 72 MV/cm)

13 GV/cm

First advantage of YbF: Huge effective field ηEParpiaQuineyKozlovTitov

2nd advantage of YbF:No coupling σ × E • v to motional magnetic field

and internuclear axis is coupled to E

E

∴< σ × E > = 0 no motional systematic error

electron spin σ is coupled to internuclear axis

σ

Yb+

F-

B and E1.5 m

The Sussex molecular beam

beam

oven

state select

polarise

analyse

detect

PMT

Part of the optical setup

Measuring the edm

Applied magnetic field

Det

ecto

r co

unt r

ate

cos2 ω+T

B0

cos2 ω−T

δφ = 4deηET/h

-B0

− 4deηET/h

Projections for the future

background

fringe height

coherence time

de in 1 day

2002result

150kHz

1.5 kHz

1.5 ms

3 10-26 e cm

cold YbFbeam

640kHz

160 kHz

1 ms

6 10-28 e cm

trappedmolecules

40kHz

10 kHz

1 s

3 10-30 e cm

long time = narrow fringes

d(muon) < 7�10-19

φ ∼ 1

Left-Right

10-20

10-22

10-24

d e.cm

MultiHiggs SUSY

φ ∼ α/π

Electro-magnetic

neutron:electron:

1960 1970 1980 1990 2000 2010 2020 2030

10-28

10-29

Current status of EDMs

d(neutron) < 6�10-

26

d(proton) < 6�10-

23YbF expt

coldmolecules

d(electron) < 1.6�10-

27

Conclusion

EDM measurements (especially cold moleules)have great potential to elucidate

• CP violation

• particle physics beyond the standard model

• matter/antimatter asymmetry of the universe

some of the most fundamental issues in physics