1. Electric dipole moment searches
Peter Fierlinger

2. Outline
Motivation
Different systems to search for electric dipole moments (EDMs)
Examples
P. Fierlinger – MeNu2013

3. Electric dipole moment
Magnetic moment
A non-zero particle EDM
violates P
… and T
(time reversal symmetry)
… assuming CPT conservation, also CP -
Purcell and Ramsey, PR78(1950)807
EDM +
P. Fierlinger – MeNu2013

4. History EDM limits [e.cm] SM neutron SM electron MSSM ~/
L-R symmetric
Multi-
Higgs
~1 e- n p
Ramsey &
Purcell (1950) n
n+Hg Xe n
e-(Tl)
EDM limits [e.cm] n
Hg `01
Hg `09
Atoms e-

5. Neutron EDM and the SM CP violation from CKM Strong Interaction
CP-odd term in Lagrangian:
Khriplovich Zhitnitsky (1986),
McKellar et al., (1987)
E.g. Pospelov, Ritz, Ann. Phys. 318(2005)119
M. Pospelov, et al., Sov. J. Nucl. Phys. 53, 638 (1991)
Neutron EDM dn  ecm (de < ecm)
dn much more difficult to calculate, but still small
Strong CP problem
T. Mannel, N. Uraltsev, Phys.Rev. D85 (2012)
P. Fierlinger – MeNu2013

6. Baryon asymmetry Remarks: Observed: nB / nγ Expected: ~ 6 x 10-10
(BBN, CMB)
Expected:
nB / nγ ~ MUCH smaller
e.g. astro-ph/
‚Ingredients‘ to model baryogenesis:
Sakharov criteria
JETP Lett. 5 (1967) 24
Remarks:
e.g. Cirigliano, Profumo, Ramsey-Musolf JHEP 0607:002 (2006)
Beyond-SM physics usually requires large EDMs
EDMs and Baryogenesis via Leptogenesis?
Also other options w/o new CP violation possible (Kostelecky, CPT)
SUSY: small CPV phases, heavy masses, cancellations?
What do we learn from an EDM?
Different measurements are needed!
P. Fierlinger – MeNu2013

7. polar / charged molecules
Physics behind EDMs dq dq ~ 
Cqe
Cqq de d d
gNN
CS,P, T
Neutron, proton
Leptons
See e.g. Pospelov, Ritz, Ann. Phys. 318(2005)119
Ions
Schiff-Moment  Z²
Schiff-Moment  Z³
Diamagnetic
atoms
Paramagnetic atoms,
polar / charged molecules
P. Fierlinger – MeNu2013

8. Atom EDM Schiff moment: Eext
Non-perfect cancellation of Eext in atomic shell
Paramagnetic atoms ~ electron EDM
Relativistic effects
Sandars, 1968
L. Schiff, Phys. Rev. 132, 2194 (1963)
Diamagnetic atoms ~ nuclear EDM
Finite size of nucleus violates Schiff‘s theorem
Eext
Schiff 1963; Sandars, 1968;
Feinberg 1977;
Large enhancements also with deformed nuclei (Ra, Rn, also Fr, Ac, Pa)
P. Fierlinger – MeNu2013

9. Atomic effects Contributions to atomic EDMs:
13 (model-dependent) parameters
TeV-scale CP odd physics, nucleon level, nucleus-level
Only 8 types of experiments
Illustration: T. Chupp et al., to be published *)
See also J. Engel, M. J. Ramsey-Musolf, U. van Kolck, Prog. Part. Nucl. Phys. 71, 21 (2013)
gπ1
gπ0
P. Fierlinger – MeNu2013

10. Measuring the neutron EDM
(RAL/SUSSEX/ILL experiment)
Ultra-cold neutrons (UCN)
trapped at 300 K in vacuum
Ekin < 250 neV
 > 50 nm
T ~mK
Storage ~ 102 s B0
~ 0.5 m
P. Fierlinger – MeNu2013

11. Ramsey‘s method EDM changes frequency:
Particle beam or trapped particles
Polarization E
1-L („detuning“)
EDM changes frequency:
P. Fierlinger – MeNu2013

12. Clock-comparison experiment
- Neutrons and 199Hg stored
in the same chamber
- Gravity changes
center of mass!
B =1 T ( + small vertical gradient)
Physical Review Letters  97 (2006)
Illustration (2008 data)
Analysis using the gradient:
B0 down
B0 up
dn < 2.9 x e cm
Applied Gradient
Requirement: 199Hg-EDM must be small: (btw., this also limits other parameters, e.g CS, CT...):
dHg < 3.1 x e cm
Frequency ratio
Hg-EDM: W. C. Griffith et al., PRL 102, (2012)
P. Fierlinger – MeNu2013

13. Neutron and proton experiments
nEDM
Cryo EDM
ILL Crystal EDM
FRM-II EDM
JPARC
NIST Crystal
PNPI/ILL
PSI EDM
SNS EDM
TRIUMF/RNPC
pEDM
Jülich
BNL
Method
4He
Solid
sD2
Cold beam
Turbine
B and E field ring
Electrostatic ring
Goal (x10-28 ecm)
~ 50; 2. < 5
< 100
< 5
< 10
1. ~ 100; 2. < 10
1. ~ 50; 2. < 5
1. R&D; ;
10-29
Comments
Larger revisions to come
Diffraction in crystal: large E
Adjustable UCN velocity
Special UCN handling
R&D
E = 0 reference cell
Phase 1 takes data
Sophisticated technology
Phase II at TRIUMF
Stepwise improvements
Completely novel technology
P. Fierlinger – MeNu2013

14. ‚Current generation‘ improvements
PSI (taken from B. Lauss, K. Kirch), for actual numbers see PSI EDM talk
PNPI/ILL (taken from A. Serebrov, 2013):
UCN density measured in a 25l volume
extrapolated to t=0
at PSI area West-1
2010 ~0.15 UCN/cm3
2011 ~18 UCN/cm3
2012 ~23 UCN/cm3
correct for detector foil transmission
status (4/2013) >33 UCN/cm3 in storage experiment (-> this is an extrapolation)
< 2 UCN/cm3 in EDM experiment
UCN density 3-4 ucn/cm3 (MAM position) Electric field 10 kV/cm T(cycle) = 65 s
...new electric field 20 kV/cm
δDedm ~ 5∙ e∙cm/day
~ 2014: EDM position at PF2
1∙ e∙cm/100 days
δDedm ~ 2.5∙ e∙cm/day 14
P. Fierlinger – MeNu2013

15. SQUID measurements of Sussex EDM electrodes @ PTB Berlin
‚Next generation‘
Most critical for next generation experiments:
‚geometric phases‘
Example:
Dipole fields in EDM chambers
20 pT in 3 cm ~ 5 x error budget!
SQUID measurements of Sussex EDM PTB Berlin
Pendlebury et al., Phys. Rev. A 70, (2004)
Magnetic field requirements
for ecm – level accuracy:
~ fT field drift error,
~ < 0.3 nT/m avg. gradients
df ~ ecm (199Hg geom. phase)
dn ~ ecm (UCN geom. phase)
~ 0.3 m
demagnetized:
20 pT pp
200 pT pp
Statistics: 103 UCN/cm3 ~ 1 year
Further: P. G. Harris et al., Phys. Rev. A 73, (2006), also: G. Pignol, arXiv: (2012).
P. Fierlinger – MeNu2013

16. New sources of UCN Superthermal solid D2 or superfluid 4He-II
SD2: Molceular excitations used to cool neutrons to zero energy -
similar: ILL, LANL, Mainz, NCSU, PNPI, PSI, TUM …
4He: ILL, KEK, SNS, TRIUMF, …
Goal of most sources:
10³ UCN /cm³
in experiment
P. Fierlinger – MeNu2013

17. Magnetic fields The smallest extended size field and gradient on earth
< 100 pT/m gradient in 0.5 m3
At FRM-II EDM setup: fields designed and measured -this technology is ready and available!
z = 0.5 m
z = 0 m (center)
z = m
x [m]
[nT]
SQUID offset in z not corrected
y [-0.5 m – 0.5 m]
P. Fierlinger – MeNu2013

18. Next generation neutron EDMs
E.g. at FRM-II (reactor):
‚Conventional‘, double chamber
UCN velocity tuning
Cs, 3He, 199Hg, 129Xe (co)magnetometers
Ready for UCN in 1 year
E.g. at SNS (spallation):
Cryogenic, double chamber
Neutron detection via spin dependent
3He absorption and scintillation
3He co-magnetometry
In the future... again nEDM with a cold beam?
Pulse structure and strong peak flux:
Cold-beam-EDM at long-pulse-neutron source (ESS) could be competitive? (Piegsa, PRC, soon...)
Re-accelerated polarized UCN with pulse-structure? (PF, in prep.)
P. Fierlinger – MeNu2013

19. Next generation nucleon EDMs
Proton, deuteron, ... EDM
Charged particle EDM searches require the development of a new class of high-precision storage rings
Projected sensitivity ~ ecm: … tests  to < 10-13!
Currently 2 approaches:
JEDI collab.: starting with COSY ring, development in stages
E, B fields
BNL: completely electrostatic, new design
all-electric ring
Requirements:
Electric field gradients 17 MV/m (possible)
Spin coherence times > 1000 s (200s demonstrated at Jülich)
Continuous polarimetry < 1 ppm error (demonstrated at Jülich)
Spin tracking simulations of 109 particles over 1000 s
P. Fierlinger – MeNu2013

20. Proton EDM in ‚magic‘ ring
- Frozen horizontal spin precession: p || s
- EDM turns s out of plane
P, S aligned
V. Bargmann, L. Michel and V. L. Telegdi, Phys. Rev. Lett. 2 (1959) 435.
Magic ring:
- Purely electric ring only for G > 0
- E and B ring for other isotopes
erklären wo der spin hindeutet
Electrostatic ring proposal at BNL
Figures: H. Stroeher
P. Fierlinger – MeNu2013

21. Octupole deformations: 225Ra
Enhancement factors: EDM (225Ra) / EDM (199Hg) ~ 103
Ra Oven:
Zeeman
Slower
Optical
dipole trap
EDM
probe
Why trap 225Ra atoms:
efficient use of the rare 225Ra atoms
high electric field (> 100 kV/cm)
long coherence times ~ 100 s
negligible “v x E” effect
Nuclear Spin = ½
t1/2 = 15 days
Schiff moment of 225Ra, Dobaczewski & Engel, PRL (2005)
Magneto-optical
trap
Goal ~ ecm
Main issue: statistics
(Project X?)
MOT: Guest et al., PRL (2007)
Dipole trap: Trimble et al. (2010)
Figures: Z.-T. Lu
P. Fierlinger – MeNu2013

22. Lepton EDM measurements
Best limits:
Mainly paramagnetic systems and polar molecules
Cs, Tl, YbF: de < ecm (E. Hinds et al.)
Soon: ThO – currently taking data
Molecules, molecular ions, solids: PbO, PbF, HBr, BaF, HgF, GGG, Gd2Ga5O12 etc.
dGGG ~ < ecm
d < (90%) ecm from g-2
d < (90%) ecm from Z
Diamagnetic atoms also
contribute to such limits!
Shapiro, Usp. Fiz. Nauk., (1968)
tau ... CP
Tl, YbF limits together,
courtesy T. Chupp (2013)
P. Fierlinger – MeNu2013

23. The ACME experiment Status: taking data with 10-28 ecm /day
ThO molecules:
100 GV/cm internal electric field due to level structure,
polarizable with very small lab-field
Small magnetic moment, therefore less sensitive to B-field quality
High Z: enhancement
Well understood system
Lasers to select states
High statistics:
strong cold beam
Status: taking data with ecm /day
Figures: J. Doyle
P. Fierlinger – MeNu2013

24. Summary
New EDM experiments are highly sensitive probes for new physics
Several experiments must be performed to understand the underlying physics. (Then, also a measured limit may be a discovery...)
Experimental techniques span from
table top AMO - solid state - low temperature – accelerators - neutron physics
Next generation precision within next
2 years: nEDM ~ few ecm
atoms ~ < ecm (ThO, 199Hg, 129Xe)
6 years: nEDM ~ few ecm
atoms - hard to predict
... Note: my nEDM time estimate stayed constant since 2009
P. Fierlinger – MeNu2013

25. New concepts? Re-acceleration of UCN
A possibility to produce extremely high brightness ‚cold‘ neutron beams:
concept demonstrated (Rauch et al.)
Next step:
Perfect polarization
(PF et al.)
S. Mayer et al., NIM A 608 (2009) 434–439
Again: nEDM measured with a cold beam?
Beam-EDM at long-pulse-neutron source could be competitive (Piegsa et al., to be published soon)
Why not use a combination: perfectly polarized, re-accelerated high brightness beam with extremely well known time structure for in-beam EDM?

26. Supersymmetry More sources of CP violation Consequences small phases:
~ EDMs at 1 loop level
MSSM example:
MSSM for
M = 1 TeV,
tan =3
Hg EDM ~ exp. Limit!
Boson coupling
Pospelov, Ritz, Ann. Phys. 318(2005)119
Consequences
small phases:
problem for baryogenesis
cancellations: requires tuning
heavy masses
Higgsino mass phase
P. Fierlinger – MeNu2013