DeMille

Group

Dave DeMillePhysics Department 

Yale University

The electric dipole moment of the electron

FundingNSF

ꞏ Electric dipole moments (EDMs) and new particle physicsꞏ How to detect an EDMꞏ Upper bound from the ACME experimentꞏ What it means, and where we go next

+ d =

CPT theorem T-violation = CP-violation

T

An EDM violates time-reversal symmetry

If all electrons look like this…

This does not existT not a good symmetry of nature

PurcellRamseyLandau

Pn.b.

inversion symmetry also broken by EDM

Q. How can a T-violating electron EDM arise?

A. From radiative corrections, with CP-violating interactions

e e

W t

bWc

W

Standard Model

4-loops for nonzero effectAND

severe cancellations in sum over all diagrams

[GIM mechanism]

CP-violating phasesfrom

CKM matrix

sg

e e

e e

~ ~

~

Supersymmetry1st order perturbation

ANDcancellations not built in

ßde de (Std. Model)

CP-violating phasefrom

SUSY-breaking

Q. How can a T-violating electron EDM arise?

A. From radiative corrections, with CP-violating interactions

Dimensional estimate for size of EDM

e

= -field

(new heavy particle)

gg

Dimensionless coupling constant T‐violating 

phase

“natural” assumptionsg2/ħc sin() ~ 1

m ~ 1 TeVei

de ~ 30× current limit

(for N = 1 loop)

typical e-EDM

N = # loops

22

~2

sinN

ee B

g mdm

Artist’s impression of an electron EDM…

Note the resemblance to 0…

any EDM must be VERY small

QED radiative correction scale[/2] B/e ~10-13 cm

:Size of earth ~104 km

::

eEDM charge displacement:

<20 nanometers

General method to detect an EDM

Energy level picture:

Figure of merit: int1

1/ /coh

coh

shift d N Tresolution S N

+2d

+2d

Bw=2mB

w=2mB

-2d

-2d

S

Amplifying the electric field with a polar molecule

eff

Th+

O–

ext

Inside polarized molecule, eEDM acted on by eff ~ P 2Z 3e/a0

2 due to relativistic motion

Small energy splittings(rotational levels)

enables polarization ~ 100% with ext ~ 10 V/cm

Requires unpaired electron spin(s): chemical free radical

P. Sandars1965

eff 80 GV/cm for ThO* [near theoretical maximum]Meyer & Bohn (2008); Skripnikov, Petrov & Titov (2013, 2015); Fleig & Nayak (2014)

Advanced Cold‐Molecule Electron EDM

Yale University Harvard University

The ACME team 2009-2014BenSpaun

Chris Overstreet Nick Hutzler Cris Panda

Jacob Baron Paul Hess Elizabeth PetrikBrendon O’Leary

John Doyle DPD

Adam West

Emil Kirilov

Yulia Gurevich

Ivan Kozyryev

Max Parsons

New molecular beam technology:Cryogenic Buffer Gas-cooled Beam (CBGB)

Liquid helium bath

or pulse‐tube refrigerator

Beam brightness [=flux/divergence] ~ 103 ‐104 larger vs. other sources for refractory/free radical species

typically  ~ 21011 mol/sr/state/pulse @ 10 Hz rep. rate

Used for SrF, ThO, BaF, YO, CaF, O2, NH3, Yb, …

• Inject hot molecules (e.g. via laser ablation)• Cool w/cryogenic buffer gas @high density• Efficient extraction to beam via “wind” in cell: 10‐4 10%‐40%

• “Self‐collimated” by extraction dynamics• Rotational cooling in expansion: T ~ 1 ‐ 4K•Moderately slow: v ~ 130‐180 m/s

[Maxwell et al. PRL 2005;  Patterson & Doyle J Chem Phys 2007;Barry et al. PCCP 2011; Hutzler et al. PCCP 2011]

“New” molecular species: ThO* • Largest effective internal : ~80 GV/cm [Titov et al. 2013/2015, Fleig et al. 2014]

• Sufficient coherence time (~1.9 ms max) lifetime of metastable state H 31

• Suppressed magnetic moment<0.01 B  in H 31 reduces B‐field systematics

[Idea: Meyer, Bohn, Cornell et al. (JILA);Measured: A.C. Vutha et al., PRA 2011]

• Omega‐doublet co‐magnetometersuppresses many possible systematics

• All spectroscopic data previously known

• State preparation and readoutw/standard, robust diode & fiber lasers

• Blue‐shifted fluorescence from probe laserno problem with backgrounds

• High beam source yieldground state

X 1

A 30

H 31

C 11

943 nmPump

1090 nm prep/probe

ThO

690 nm detect

[A.C. Vutha et al. J. Phys B 2010]

EDM measurement with -doublet states

m = 0ext

+

-eff

+

-

eff

+

-eff

+

-

eff

m = -1 S m = +1 SJ=1-

J=1+

+

- +

-+

+

- +

-

-

S S

S S

many dangeroussystematic errors cancel

in comparisonbetween

(near-)mirror image = 1 states

[DD et al., AIP Conf. Proc.

596, 2001]

= -1

= +1

ACME experimental schematic

ACME apparatusMolecular

BeamSource

Pulsed ablation

laser

Prep Lasers

Probe Lasers

Pulse Tube Cryo Frig

Interaction Region: internal -field plates & external

B-field coils (not shown here)

"

ITO Coated Borofloat glass

Molecule Beam E, B,

Transparent Field Plates

μ-metal shield endcaps(5 layers)

ACME apparatusMagnetic field coils

(3 orthogonal components& all first-order gradients)

.001 km

Completebeam source

& magnetic shields& last-stage optics

ACME apparatus

One of several optical tables w/~ten lasers, dozens of modulators,

hundreds of meters of optical fiber, etc.spread over two buildings

“control room”

Typical spin-rotation fringe signal

Take EDM dataat any of these points

B=0 ‐B

+Bsets = /2

( )cos 22f q= -

Contrast ~ 95%

Take data here

Final spin angle  dvs. probe laser polarization angle 

Spin‐rotation sig

nal 

Primary machine settings to extract the EDM

--psuedo-random (pair-wise), interleaved reversals

Data sorting & systematic error analysis

Switch-correlated phases measure physical contributions:

0

1 1...

2 2nr

e eff N H leak N H nrd g gf m m+ D+µ D +

EDM

Symmetries ensure systematic errorsdue ONLY to experimental imperfections e.g.

--leakage current-induced -field leak --non-reversing -field nr

--etc.

Rewrite phase as components correlated w/switches:

EDM phaseSuperscipt means

“odd under this reversal” other phases to diagnose systematics

Spurious terms

0

1 1...

2 2

nr

e eff H lea rH nk Nd g gf m m+ D + +µ D

Data analysis: diagnosing imperfections

EDMExperimental imperfections

12 H leakgf mµ

0

12

nrN Hgf mµ D

Most imperfections also appear in other correlated phasesBUT GREATLY AMPLIFIED

/ ~ 1000N

g gD / ~ 1000nr

“Other” correlated phases diagnose imperfections

Switch-correlated phases isolate physical contributions:

Search strategy for systematic errorsSwitch-correlated phases isolate physical contributions:

0

1 12 2

nre eff N H leak N nrHd g gf m mµ D+ + +D ...

EDMExperimental imperfections

Strategies:

Change all possible parameters that shouldn’t affect EDM ( magnitude, magnitude, global polarization, etc. etc.)

but might couple to unanticipated imperfections

Deliberately amplify imperfections, understand any changes in correlated phases

But… what about terms we don’t anticipate?

stat 3.7 ∗ 10 cm

stat

ACME electron EDM data

Blind analysis: randomly chosen offset added to data until analysis complete

???

stat 3.7 ∗ 10 cm

stat

ACME electron EDM data

Blind analysis: randomly chosen offset added to data until analysis complete

Consistent with zero set upper limit

J. Baron et al.,Science (2014)

New upper bound on electron EDM from ACME

10-4110-4010-3410-3310-3210-3110-3010-2910-2810-2710-2610-25

de (ecm)

Heavy sFermions

Model

Left Right Symmetric

Accidental Cancellations

Berkeley(2002)

ExactUniversality

Seesaw Neutrino Yukawa Couplings

Lepton FlavorChanging

Approx. CP

SO(10) GUT

10-10-10-3410-3310-3210-3110-3010-2910-2810-2710-2610-25

de (ecm)

Standard Model

ExactUniversality

Approx. Universality

Alignment

~

Left Right Symmetric

Lepton FlavorChanging

Accidental Cancellations

SO(10) GUT

Approx. CP

Heavy sFermions

Seesaw Neutrino Yukawa Couplings

MultiHiggs

Split SUSY

ve SUSYïNa

Imperial(2011)

ExtendedTechnicolor

ACME(2013)

YalePbO*2013

-

--

• ~10-fold improvement• extends deep into expected ranges• limited by statistics

Impact of EDMs in particle physicsJ. Feng: “Naturalness and the status of SUSY”, Annu. Rev. Nucl. Part. Sci. (2013)

EDM results push SUSY scale into “unnatural” regions--potential for imminent discovery…?

“All of the constraints shown are merely indicative and subject to

significant loopholes and caveats”

ACME (electron), 2014Seattle

(199Hg)2016 199Hg

ACME

Reece & NakaiarXiv: 1612:09080

th

Diagrams withknown SM particles

can rule outnon-SM couplings

Example:CP-violating

Higgs-top couplingBrod et al.,

arXiv: 1310.1385

CP-odd/CP-even Higgs-top coupling <1% from ACME

LHCConstraint

ACME Constraint

What does the eEDM limit mean for particle physics?

Impact of EDMs in particle physics(A very generic view)

Plot courtesy of M. Reece (Harvard)

The ACME II team

Brendon O’Leary

John Doyle

Adam West

CrisPandaZack

Lasner

Daniel AngVitaly Andreev

Gerald Gabrielse

DD

Elizabeth Petrik

Jonathan Haffner

NickHutzler

(Caltech)

ColeMeisenhelder

XingWu

ACME II statistical sensitivity

ACME II statistical sensitivity

~10x improved EDM statistical sensitivity/unit timeSystematic error studies ~complete, final data taking underway

Near-future discovery potential with the electron EDM

ACME II

ACME Ultimate