Electric dipole moment searches
Peter Fierlinger
Outline
Motivation
Different systems to search for electric dipole
moments (EDMs)
Examples
P. Fierlinger – MeNu2013
Electric dipole moment
Magnetic
moment
A non-zero particle EDM
violates P
EDM
+
Purcell and Ramsey, PR78(1950)807
… and T
(time reversal symmetry)
… assuming CPT
conservation, also CP
P. Fierlinger – MeNu2013
History
L-R symmetric
n
MSSM
~1
p
EDM limits [e.cm]
n
n+Hg
Xe
e-(Tl)
en
MultiHiggs
n
Hg `01
Hg `09
Atoms
MSSM
~/
eSM neutron
SM electron
Neutron EDM and the SM
Strong Interaction
CP-odd term in Lagrangian:
s ~
L  
GG
8
M. Pospelov, et al., Sov. J. Nucl. Phys. 53, 638 (1991)
d n ( ) ~ 
Neutron EDM dn  10-32 ecm (de < 10-38 ecm)
- dn much more difficult to calculate, but still
small
T. Mannel, N. Uraltsev, Phys.Rev. D85 (2012) 096002
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e m*
~ 6.1017  e  cm
mn QCD
  10
10
Strong CP problem
E.g. Pospelov, Ritz, Ann. Phys. 318(2005)119
Khriplovich Zhitnitsky (1986),
McKellar et al., (1987)
CP violation from CKM
Baryon asymmetry
Observed: nB / nγ
~ 6 x 10-10
(BBN, CMB)
e.g. astro-ph/0603451
JETP Lett. 5 (1967) 24
‚Ingredients‘ to model baryogenesis:
Sakharov criteria
Remarks:
- 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
e.g. Cirigliano, Profumo, Ramsey-Musolf JHEP 0607:002 (2006)
Expected:
nB / nγ ~ MUCH smaller
dq d~q 
Neutron,
proton
Ions
de d d
Cqe Cqq
gNN
CS,P, T
Schiff-Moment  Z²
Diamagnetic
atoms
Leptons
Schiff-Moment  Z³
Paramagnetic atoms,
polar / charged molecules
P. Fierlinger – MeNu2013
See e.g. Pospelov, Ritz, Ann. Phys. 318(2005)119
Physics behind EDMs
Atom EDM
Non-perfect cancellation of Eext in atomic shell
Paramagnetic atoms ~ electron EDM
Relativistic effects
d a  de Z 3
Sandars, 1968
Diamagnetic atoms ~ nuclear EDM
Finite size of nucleus violates Schiff‘s theorem
da  dnucl Z 2
Eext
Schiff 1963; Sandars, 1968;
Feinberg 1977; ... - 2010
Large enhancements also with deformed nuclei
(Ra, Rn, also Fr, Ac, Pa)
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L. Schiff, Phys. Rev. 132, 2194 (1963)
Schiff moment:
Atomic effects
-
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
*)
gπ1
See also J. Engel, M. J. Ramsey-Musolf, U. van Kolck, Prog. Part. Nucl. Phys. 71, 21 (2013)
Contributions to atomic EDMs:
gπ0
P. Fierlinger – MeNu2013
Measuring the neutron EDM
Ultra-cold neutrons (UCN)
trapped at 300 K in vacuum
Ekin < 250 neV
 > 50 nm
T ~mK
Storage ~ 102 s
~ 0.5 m
P. Fierlinger – MeNu2013
(RAL/SUSSEX/ILL experiment)
B0
Ramsey‘s method
Polarization
Particle beam or trapped particles
E
1-L („detuning“)
d 
n
EDM changes frequency:
w L ~ mB + dE
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2 ET N
Clock-comparison experiment
- Neutrons and 199Hg stored
in the same chamber
B =1 T ( + small vertical gradient)
Applied Gradient
Illustration (2008 data)
B0 up
B0 down
Analysis using the gradient:
dn < 2.9 x 10-26 e cm
Physical Review Letters 97 (2006) 131801.
- Gravity changes
center of mass!
Requirement: 199Hg-EDM must be small:
(btw., this also limits other parameters, e.g CS, CT...):
Frequency ratio
dHg < 3.1 x 10-29 e cm
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Hg-EDM: W. C. Griffith et al., PRL 102, 101601 (2012)
Neutron and proton experiments
nEDM
Method
Goal (x10-28 ecm)
Comments
Cryo EDM
4He
1. ~ 50; 2. < 5
Larger revisions to come
ILL Crystal EDM
Solid
< 100
Diffraction in crystal: large E
FRM-II EDM
sD2
<5
Adjustable UCN velocity
JPARC
sD2
< 10
Special UCN handling
NIST Crystal
Cold beam
< 10
R&D
PNPI/ILL
Turbine
1. ~ 100; 2. < 10
E = 0 reference cell
PSI EDM
sD2
1. ~ 50; 2. < 5
Phase 1 takes data
SNS EDM
4He
<5
Sophisticated technology
TRIUMF/RNPC
4He
< 10
Phase II at TRIUMF
Jülich
B and E field ring
1. R&D; 2. 10-24; 3. 10-29
Stepwise improvements
BNL
Electrostatic ring
10-29
Completely novel technology
pEDM
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‚Current generation‘ improvements
PSI (taken from B. Lauss, K. Kirch), for actual numbers see PSI EDM talk
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
PNPI/ILL (taken from A. Serebrov, 2013):
UCN density 3-4 ucn/cm3 (MAM position)
Electric field 10 kV/cm
T(cycle) = 65 s
δDedm ~ 5∙10-25 e∙cm/day
...new electric field 20 kV/cm
δDedm ~ 2.5∙10-25 e∙cm/day
P. Fierlinger – MeNu2013
~ 2014: EDM position at PF2
1∙10-26 e∙cm/100 days
14
‚Next generation‘
Example:
Dipole fields in EDM chambers
SQUID measurements of Sussex
EDM electrodes @ PTB Berlin
Magnetic field requirements
for 10-28 ecm – level accuracy:
~ fT field drift error,
~ < 0.3 nT/m avg. gradients
df ~ 4.10-27 ecm (199Hg geom. phase)
dn ~ 1-2.10-28 ecm (UCN geom. phase)
Statistics: 103 UCN/cm3 ~ 1 year
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~ 0.3 m
Pendlebury et al., Phys. Rev. A 70, 032102 (2004)
Most critical for next generation experiments:
‚geometric phases‘
200 pT pp
demagnetized:
20 pT pp
20 pT in 3 cm ~ 5 x error budget!
Further: P. G. Harris et al., Phys. Rev. A 73, 014101 (2006),
also: G. Pignol, arXiv:1201.0699 (2012).
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
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 = - 0.5 m
x [m]
[nT]
SQUID offset in z
not corrected
y [-0.5 m – 0.5 m]
P. Fierlinger – MeNu2013
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
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 ~ 10-29 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
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Proton EDM in ‚magic‘ ring
Thomas-BMT equation
p || s
(Bargmann, Michel, Telegdi)
ds
dt
= Ω ×ds =s Ω × s
Ω=
dt
e Ω = e [GB + G − 121
1 + v × B)]
v × E + 1 η(E
mc [GBmc+ G − γ 2γ− −11 v × E 2+ 2 η(E + v
d= η
d= η
e
S,
2mc
µ = 2(G + 1)
e
S,
2m
e
e
S, µ = 2(G + 1)
S,
d: electric dipole moment
2mc
2m
G=
g− 2
,
2 g
G=
× B)]
−2
,
2
µ: magnetic moment, g:g− factor , G: anomalous magnetic
Magic
ring:
moment
d: electric
dipole moment
γ: Lorentz factor
-µ:Purely
>0
magneticelectric
moment,ring
g:g− only
factor for
, G: G
anomalous
magnetic
-moment
E and B ring for other isotopes
V. Bargmann, L. Michel and V. L. Telegdi, Phys. Rev. Lett. 2 (1959) 435.
γ: Lorentz factor
20 / 50
V. Bargmann, L. Michel and V. L. Telegdi, Phys. Rev. Lett. 2 (1959) 435.
Electrostatic ring
proposal at BNL
20 / 50
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Figures: H. Stroeher
V. Bargmann, L. Michel and V. L. Telegdi, Phys. Rev. Lett. 2 (1959) 435.
- Frozen
horizontal
spin precession:
Spin
Motion is governed
by Thomas-BMT
Thomas-BMT
equation equation
(Bargmann,
Michel,
Telegdi)
- EDM
turns
s out
of plane
Spin Motion
is governed
by Thomas-BMT
equation
Octupole deformations: 225Ra
Ra Oven:
Nuclear Spin = ½
t1/2 = 15 days
Dipole trap: Trimble et al. (2010)
MOT: Guest et al., PRL (2007)
- Goal ~ 10-28 ecm
- Main issue: statistics
(Project X?)
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
Zeeman
Slower
Magneto-optical
trap
EDM
probe
Optical
dipole trap
P. Fierlinger – MeNu2013
Figures: Z.-T. Lu
Schiff moment of 225Ra, Dobaczewski & Engel, PRL (2005)
Enhancement factors: EDM (225Ra) / EDM (199Hg) ~ 103
Lepton EDM measurements
Best limits:
Shapiro, Usp. Fiz. Nauk., 95 145 (1968)
Mainly paramagnetic systems and polar molecules
- Cs, Tl, YbF: de < 1.05.10-27 ecm (E. Hinds et al.)
- Soon: ThO – currently taking data
- Molecules, molecular ions, solids: PbO, PbF, HBr, BaF, HgF, GGG,
Gd2Ga5O12 etc.
- dGGG ~ < 10-24 ecm
- d < 1.8 . 10-19 (90%) ecm from g-2
- d < 1.7 . 10-17 (90%) ecm from Z
Diamagnetic atoms also
contribute to such limits!
Tl, YbF limits together,
courtesy T. Chupp (2013)
P. Fierlinger – MeNu2013
The ACME experiment
-
-
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 10-28 ecm /day
P. Fierlinger – MeNu2013
Figures: J. Doyle
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 10-27 ecm
atoms ~ < 1.10-29 ecm (ThO, 199Hg, 129Xe)
6 years: nEDM ~ few 10-28 ecm
atoms - hard to predict
... Note: my nEDM time estimate stayed constant since 2009
P. Fierlinger – MeNu2013
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.)
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, reaccelerated high brightness beam with extremely well
known time structure for in-beam EDM?
S. Mayer et al., NIM A 608 (2009) 434–439
New concepts?
Supersymmetry
More sources of CP violation
~ EDMs at 1 loop level
dn  1026 1028 ecm
2
d Hg
 1 T eV
 2 10 
 ecm
M


27
Boson coupling
Hg EDM ~ exp. Limit!
MSSM for
M = 1 TeV,
tan =3
Consequences
- small phases:
problem for baryogenesis
- cancellations: requires tuning
- heavy masses
P. Fierlinger – MeNu2013
Higgsino mass phase
Pospelov, Ritz, Ann. Phys. 318(2005)119
MSSM example: