Proton EDM search with cold molecules

Tanya Zelevinsky &

CeNTREX Collaboration

Columbia University, New York

CeNTREX = Cold molecule Nuclear Time Reversal EXperiment

Fundamental symmetries with

quantum science techniquesSearch for T-reversal symmetry violating forces

Tabletop scale experiments

Exceed the energy reach of LHC

10,000,000,001 10,000,000,000

Matter Antimatter

Could explain 10-10 asymmetry,

measured from photon-baryon ratio

Searching for new T-violating interactions

Equal amounts of

matter and antimatter

NAIVE EXPECTATION: OBSERVED

:Mostly photons; little matter;

almost no antimatter

photons

matter

antimatter

• T-violation required to explain the baryon asymmetry

• T-violation in Standard Model is too small by orders of magnitude

• Need new T-violating forces associated with new particles of ~TeV mass

• Standard Model extensions

A. Sakharov, JETPL 5, 27 (1967)

Charge asymmetry violates T, P

Size of charge asymmetry depends on mass of new particles:

Larger effect for lighter virtual particles, or simpler processes

+ +

- -

T + +

- -≠

+ +

- -

m

EDM

Searching for new T-violating interactions

J. Feng, ARNPS 63, 351 (2013)

0.3 1 3 10 30

Superpartner mass (TeV)

𝑢 , ෩𝑑 , 𝑒

LHC

Atom,

molecule,

neutron

EDMs

Natural scale

for supersymmetry

Projected

EDMs

Sensitivity to particles that mediate T-violating forces

TeV

Energy

nuclear

atomic

Fundamental CP phases

EDMs of diamagnetic atoms

(Hg, Ra)and molecules (TlF)

Nucleon EDMs (n, p)

EDMs of paramagneticatoms and molecules

(Cs, Fr, Tl, YbF, ThO, HfF+),solid state

e EDMθQCD,

quark EDMs,CEDMs

Leptonic

Leptonic and hadronic EDMs

Hadronic

Quantum mechanics (Schiff theorem) & simple reasoning →

𝐸 = 0on pointlike, nonrelativistic charged particle

within neutral atom or molecule

Loopholes lead to observable atomic & molecular EDMs:

• Electron relativistic motion → eEDM de

• Nucleus finite size → Schiff moment S nEDM or pEDM

Molecules are ~105× more polarizable than atoms

Origin of EDMs in atoms and molecules

Search for a nuclear charge asymmetrySchiff moment in 205Tl nucleus, shows up in TlF molecules

Torque from intramolecular E-field →

precession of nuclear spin

Tl

F

Ԧ𝑑𝑆𝑀

Ԧℰ𝑙𝑎𝑏 ∼ 104 V/cmԦℰ𝑖𝑛𝑡

F nuclear spin:

• Low Z → small EDM

• Co-magnetometer to

suppress systematics

Search for a nuclear charge asymmetrySchiff moment in 205Tl nucleus, shows up in TlF molecules

𝛿𝑑𝑆𝑀~ℏ

ℰ𝑒𝑓𝑓𝜏 𝑁Measurement sensitivity

Ԧℰ𝑖𝑛𝑡 = 0

Ԧ𝑑𝑆𝑀 ⋅ Ԧℰ𝑖𝑛𝑡 = 𝑑𝑆𝑀ℰ𝑒𝑓𝑓 ≠ 0

Intramolecular field at nucleus:

Tl

F

Ԧ𝑑𝑆𝑀

Cryogenic molecular beam

Laser detection

& cooling

t ~ 20 ms

ሶ𝑁 > 107/ s

100% molecules

detected

ℰ𝑒𝑓𝑓 ∼ 30 kV/cm

finite

nuclear size

<10-30 ecm

Search for a nuclear charge asymmetrySchiff moment in 205Tl nucleus, shows up in TlF molecules

𝛿𝑑𝑆𝑀~ℏ

ℰ𝑒𝑓𝑓𝜏 𝑁Measurement sensitivity

Ԧℰ𝑖𝑛𝑡 = 0

Ԧ𝑑𝑆𝑀 ⋅ Ԧℰ𝑖𝑛𝑡 = 𝑑𝑆𝑀ℰ𝑒𝑓𝑓 ≠ 0

Intramolecular field at nucleus:

D. Cho et al., PRA 44, 2783 (1991)D. Wilkening et al., PRA 29, 425 (1984)E. Hinds and P. Sandars, PRA 21, 480 (1980)

Tl

F

Ԧ𝑑𝑆𝑀

Cryogenic molecular beam

Laser detection

& cooling

t ~ 20 ms

ሶ𝑁 > 107/ s

100% molecules

detected

New

methods

ℰ𝑒𝑓𝑓 ∼ 30 kV/cm

finite

nuclear size

• Tl is sensitive to Schiff moment (∝ 𝐴2/3 𝑍2)

• Polarization ~0.5 at E ~30 kV/cm: ~104 relative to 199Hg

• Quasi-cycling optical transition

• Can use electronic ground state

• 19F nuclear spin: small EDM, internal co-magnetometer

• High yield from cryogenic buffer-gas beam source

• Spectroscopy and sensitivity well-known from past work

Advantages of TlF molecules

CeNTREX sensitivity to hadronic EDM

Generation I

Projected 30× sensitivity improvement in qQCD

and proton EDM

compared to 199Hg

parametrizes the

allowed CP violation

B. Graner et al., PRL 116, 161601 (2016)

~ 0.2 mHz @ T ~ 300 hours integration time

Generation II

Additional 10-100 improvement from laser cooling

J. M. Pendlebury et al., PRD 92, 092003 (2015)

Experiment design

Experiment design

• Ablated TlF entrained in 16 K neon

• ~1011 molecules / s / quantum state, pulsed

• ~200 m/s

Cryogenic beam source

The cold cell is kept at 16 K;

neon buffer gas flows through the cell

A focused laser pulse ablates a

solid TlF target,

introducing hot TlF molecules

Hot TlF are cooled by neon.

~10% of TlF molecules leave the cell,

forming the molecular beam

Experiment design

• Collect population in J = 0, F = 0

• Laser + mwaves

• E = B = 0

𝑋1Σ+

𝐵3Π+

13 GHz

27 GHz

40 GHz

271 nm

J = 1

J = 2

J = 1

J = 0

J = 3

Rotational cooling

At ~5 K, most molecules are in J = 0 ~ 5

Experiment design

• Move population to J = 2 for optimal downstream focusing

• J = 2 preparation: mwaves, E = 100 V/cm, B = 0

• Electrostatic lens: 30 kV/cm, B = 0

𝑋1Σ+

13 GHz

27 GHzJ = 2

J = 1

J = 0

Electrostatic molecule lens

Move molecules to J = 2, for a large restoring force

𝑋1Σ+

13 GHz

27 GHzJ = 2

J = 1

J = 0

Electrostatic molecule lens

Move molecules to J = 2, for a large restoring force

quadrupole potential

Quadratic Stark shift for J = 2

𝑋1Σ+

13 GHz

27 GHzJ = 2

J = 1

J = 0

Electrostatic molecule lens

Move molecules to J = 2, for a large restoring force

quadrupole potential

30

enhancement

Experiment design

• Move population to J = 1 science state

• mwaves

• E = 1 kV/cm, B = 20 G

Experiment design

• 3 m long spin-precession region

• 30 kV/cm electrodes for uniform E-field

• RF & static B-field coils, B 0

• Magnetic shielding

• >3 long, 30 cm diameter

vacuum glass tube

• Metal endcaps for sealing and

electrical connections

• Magnetic shielding: Metglas,

high-permeability

amorphous metal alloy

• Machined glass electrodes

with graphite coating for low

magnetic noise, 30 kV/cm

Interaction region

𝑋1Σ+

27 GHzJ = 2

J = 1

• >3 long, 30 cm diameter

vacuum glass tube

• Metal endcaps for sealing and

electrical connections

• Magnetic shielding: Metglas,

high-permeability

amorphous metal alloy

• Machined glass electrodes

with graphite coating for low

magnetic noise, 30 kV/cm

Interaction region

3 m long E-field plates,

separated by 2 cm

Experiment design

• Map nuclear-spin precession states onto J = 1, 2

• mwaves

• E = 1 kV/cm, B = 20 G

Experiment design

• Lasers + mwaves detect both spin states

• Cycling fluorescence detected, 100 UV photons / molecule

• E = B = 0

Optical cycling in molecules

E. Norrgard et al., PRA 95, 062506 (2017)

Scattering ~100 photons in TlF:

fluorescence detection & laser cooling

l = 272 nm

L. Hunter et al., PRA 85, 012511 (2012)

Optical cycling in molecules

T. Wright, B.S. Thesis, Amherst College (2018)

Scattering ~100 photons in TlF:

fluorescence detection & laser cooling

3 excited states

12 ground states

3 bright states

9 dark states

22 kHz

176 kHz

15 kHz

Optical cycling in molecules

T. Wright, B.S. Thesis, Amherst College (2018)

Scattering ~100 photons in TlF:

fluorescence detection & laser cooling

Polarization dark states:

remix via

polarization modulation

Optical cycling in molecules

T. Wright, B.S. Thesis, Amherst College (2018)

Scattering ~100 photons in TlF:

fluorescence detection & laser cooling

Hyperfine dark states:

remix via

microwaves to J = 0

@ 13 GHz

Optical cycling in molecules

T. Wright, B.S. Thesis, Amherst College (2018)

Scattering ~100 photons in TlF:

fluorescence detection & laser cooling

Polarization-modulation + microwave

dark-state remixing

molecular

beam

optical

passes

Only ~40 photons/molecule

Scattering rate:

1/10 of Gmax = G Ne / (Ne+Ng)

OK for efficient detection &

rotational cooling

• Laser sidebands spaced by g = 1.6 MHz cover Doppler width

• Multipass arrangement, uniform laser intensity

• Optical polarization switching @ 1 MHz

• Dark-state-mixing mwave polarization switching @ 1 MHz

43 photons

Optical cycling in TlF

L. Hunter (Amherst Colege)

(calibration)

Cryogenic beam source Rotational cooling Electrostatic quadrupole lens

3x tunable UV laser systems Stable frequency reference

CeNTREX under construction

pulse tube

refrigerators

UV laser

directed

through the

beam source

turbopump

optical

detection

flange for

molecular

beam output

Cryogenic molecular beam source

Chamber with

buffer-gas cell

and shields

cell assembly

4K shield

40K

shield

vacuum

chamber

Cryogenic molecular beam source

ablation

light enters

molecules

exit

laser port

Rotational cooling

J = 1 2

27 GHz

mwave horns

J = 2 3

40 GHz

mwave horns

J = 0 1

13 GHz

mwave horn

System 199Hg n 205TlF

Latest result 2016 2006(2015) Projected, 2021 Improvement

Sens. to QCD

q param.

𝜕𝜈/𝜕𝜃

0.1 Hz 300 Hz 105 Hz

Sens. to

quark

chromo-EDM

𝜕𝜈/𝜕 ሚ𝑑𝑞

11016 Hz/[e·cm] 21018 Hz/[e·cm] 21020 Hz/[e·cm]

Sens. to p/n

EDM 𝜕𝜈/𝜕𝑑𝑝/𝑛11015 Hz/[e·cm] 21018 Hz/[e·cm] 61018 Hz/[e·cm]

Limit on 𝜃 < 110-10 < 210-10 < 210-12 30

Limit on ሚ𝑑𝑞(cm)

ሚ𝑑𝑢 − ሚ𝑑𝑑< 1.510-27

0.5 ሚ𝑑𝑢 + ሚ𝑑𝑑< 310-26

ሚ𝑑𝑢 + ሚ𝑑𝑑< 110-27

1.5*-30

Limit on

𝑑𝑛(e·cm)<610-26 <310-26 Not competitive

Limit on

𝑑𝑝(e·cm)<910-25 Not competitive <310-26 30

*sensitive to a linear combination of parameters nearly orthogonal to comparison

Projected sensitivity comparisons

Principal Investigators

David DeMille

(Yale)

David Kawall

(UMass)

Tanya Zelevinsky

(Columbia)

Postdoc

J. Olivier Grasdijk

(Yale)PhD students

Konrad

Wenz

(Columbia)

Oskari

Timgren

(Yale)

Jakob

Kastelic

(Yale)

Tristan

Winick

(UMass)

Trevor

Wright

(Yale)

Mick

Aitken

(Columbia)

Steve Lamoreaux

(Yale)

CeNTREX teamFunding:

NSF,

Templeton,

Heising-Simons