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Electron EDM search with PbO. ·   review: basic ideas, previous results ·   work towards EDM data ·   current status: reduction in anticipated sensitivity ·   a new approach, thwarted ·   hope for the future…. D. DeMille Yale Physics Department University.

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electron edm search with pbo
Electron EDM search with PbO

·  review: basic ideas, previous results

·  work towards EDM data

·  current status: reduction in anticipated sensitivity

·  a new approach, thwarted

·  hope for the future….

D. DeMille

Yale Physics Department University

Funding: NSF, Packard Found., CRDF, NIST, Sloan, Research Corp.

general method to detect an edm



E

E

B

-2dE

+2dE

S



w

-2dE

+2dE

General method to detect an EDM

Energy level picture:

Figure of

merit:

the problem s with polar molecules
The problem(s) with polar molecules:

 Molecules with electron spin are thermodynamically disfavored

(free radicals)  high temperature chemistry, even smaller signals

 Diluted signals due to

thermal distribution over rotational levels (~10-4)

Addressing the problems with metastable PbO a(1)[3+]

·PbO is thermodynamically stable (routinely purchased and vaporized)

a(1) populated via laser excitation(replaces chemistry)

a(1) has very small -doublet splitting

complete polarization with very small fields (~10 V/cm),

equivalent to E  107 V/cm on an atom!

 can work in vapor cell

(MUCH larger density and volume than beam)

PbO Cell: Tl Beam:

N = nV ~ 1016 N = nV ~ 108

amplifying the electric field e with a polar molecule
Amplifying the electric field Ewith a polar molecule

Eext

Pb+

Complete polarization

of PbO* achieved with

Eext ~ 10 V/cm

Eint

O–

Inside molecule, electron feels internal field

Eint ~ 2Z3 e/a022.1(b) - 4.0(a) 1010 V/cm in PbO*

(a)Semiempirical: M. Kozlov & D.D., PRL 89, 133001 (2002);

(b)Ab initio: Petrov, Titov, Isaev, Mosyagin, D.D., PRA 72, 022505 (2005).

spin alignment molecular polarization in pbo no edm

J=1-

J=1+

Brf  z

a(1)

[3+]

E

B

S

S

m = -1

m = 0

m = +1

-

S

 || z

+

X, J=0+

n

n

-

-

-

-

+

+

+

+

-

-

-

-

n

n

+

+

+

+

Spin alignment & molecular polarization in PbO (no EDM)
edm measurement in pbo

E

B

E

E

E

n

n

-

-

+

+

-

-

n

n

+

+

EDM measurement in PbO*

Novel state structure allows extra reversal of EDM signal

“Internal

co-magnetometer”:

most systematics

cancel in

comparison

proof of principle setup top view
Proof-of-principle setup (top view)

Larmor

Precession

 ~ 100 kHz

B

E

PMT

Vacuum chamber

solid quartz

light

pipes

quartz oven structure

PbO vapor cell

Data

Processing

Pulsed Laser Beam

5-40 mJ @ 100 Hz

 ~ 1 GHz

  B

Vapor cell technology allows high count rate

(but modest coherence time)

laser only spin preparation for proof of principle

J=1-

vibrational substructure

J=1+

570 nm

S

S

m = -1

m = +1

548 nm

Laser-only spin preparation for proof of principle

rotational substructure

m = 0

a(1)

[3+]

 || x

X, J=0+

zeeman quantum beats in pbo g factors
Zeeman quantum beats in PbO: g-factors
  • Gives info on:
  • Density limits
  • S/N in frequency extraction
  • g-factors
  • E-field effects
  • Problems with fluorescence quantum beats:
  • Poor contrast C~10%
  • Backgrounds from blackbody, laser scatter  reduced collection
  • Poor quantum efficiency for red wavelengths
verification of co magnetometer concept

Zeeman splitting ~ 450 kHz

Verification of co-magnetometer concept

~11 MHz RF E-field

drives transitions

Zeeman splitting slightly different in lower level

g/g =

1.6(4) 10-3

 -doublet will be near-ideal

co-magnetometer

Also:

W= 11.214(5) MHz;

observed low-field

DC Stark shift

~1.6 ppt shift

in Zeeman

beat freq.

status in 2004 a proof of principle

[D. Kawall et al., PRL 92, 133007 (2004)]

Status in 2004: a proof of principle
  • PbO vapor cell technology in place
  • Collisional cross-sections as expected anticipated density OK
  • Signal size, background, contrast:
  • Many improvements needed to reach target count rate & contrast
  • Shot-noise limited frequency measurement
  • using quantum beats in fluorescence
  • g-factors of -doublet states match precisely: geff/g < 510-4
  • systematics rejection from state comparison very effective
  • E-fields OK: no apparent problems
  • EDM state preparation not demonstrated
  • EDM-generation cell & oven needed
pbo vapor cell and oven
PbO vapor cell and oven

Sapphire

windows

bonded to ceramic frame with

gold foil “glue”

Gold foil electrodes and “feedthroughs”

Opaque quartz oven body:

800 C capability;

wide optical access;

non-inductive heater;

fast eddy current decay

w/shaped audio freq. drive

state preparation rotational raman excitation

laser-prepared

superposition, as in proof-of-principle

(no good for EDM)

J=2

28.2 GHz

28.2-.04 GHz

40 MHz

J=1

laser + wave

preparation,

as needed for EDM

State preparation: rotational Raman excitation

Doesn’t

work!?!

quasi optical microwave delivery
Quasi-optical microwave delivery

“Dichroic” beamsplitter

separates

laser & microwave beams

Laser beam overlaps

with microwave beam

PbO cell

Quartz lightpipes =

multi-mode quasi-optical “fibers” for microwaves

s n enhancements far less than anticipated
S/N enhancements—far less than anticipated

Bottom line: only ~2x improvement over Tl expected with current setup  --taking data soon

laser double resonance detection

C’

Excite: X→a→C’ ( = 548 +1114 nm)

Detect: C’→a ( = 380-450 nm)

a

arbitrary units

X

10

20

30

40

50

60

70

  • Dramatic reduction of blackbody, laser scatter
  • ~8x contrast
  • ~2x quantum eff.

a

Laser double-resonance detection

Excite: X→a ( = 548 nm)

Detect: X→a ( = 570 nm)

arbitrary units

X

10

20

30

40

50

60

70

s

m

a sad story double resonance detection doesn t work

|—>-|+>/2

|—>+|+>/2

|—>

|+>

A sad story: double-resonance detectionDOESN’T WORK!*&%!

C’

Transition

Probability

|+>

1+cos(t)

|—>

1+cos(t) [+]

+

1-cos(t) [-]

=1!!!

phase

difference

eit

a

back to the future absorption detection w microwaves

A

  • Dominant noise from thermal  carrier: cancellation via “bridge” (= dark fringe interferometer)
  • Shot noise limit with ~1015 wave /shot looks feasible
  • Enhanced absorption with resonant cavity: S/N Q
Back to the future: absorption detection w/microwaves
  • long cylindrical cell for increased absorption path
  •  P/P ~ 10-4 (cross-section & density well-known)
  • P ~ 100 W in cell for no saturation
schematic of planned absorption detection scheme

J=2

Schematic of planned absorption detection scheme
  • Long cell  minimal effect of leakage currents,
  • easier heating & shielding
  • Bottom line: de 10-29 ecm looks feasible!
  • (50 cm long cell, Q = 100, shot-noise limited)

“bridge”

lens

Mixer/ detector

Magic tee

horn

lens

cavity mirror

28.2 GHz

~15 cm diam.

50 cm long

alumina tube cell

cavity mirror

horn

Magic tee

cos voltage on

rod electrodes

for transverse E-field

J=1

status of electron edm search in pbo
Status of electron EDM search in PbO
  • Current version with fluorescence detection set to take data soon (~end of summer?)
  • All major parts in place, but projected sensitivity (statistical) now only ~2x beyond current Tl result
  • Major redesign for 2nd generation experiment based on long cell + microwave absorption underway
  • Projected 2nd generation sensitivity well beyond 10-29 ecm (better estimate to come soon…)
the pbo edm group
The PbO EDM group

Postdocs:

(David Kawall)

(Val Prasad)

Grad students:

(Frederik Bay)

Sarah Bickman

Yong Jiang

Paul Hamilton

Undergrads:

Robert Horne

Gabriel Billings

Collaborators:

Rich Paolino

(USCGA)

David Kawall

(UMass)

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