edm searches - triumf · 2019. 9. 27. · very stringent edm limits of diamagnetic atoms with...

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Guillaume Pignol, August 3, 2019 IUPAP Nuclear Science Symposium, Notre Dame, London EDM searches , a worldwide perspective

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  • Guillaume Pignol, August 3, 2019IUPAP Nuclear Science Symposium, Notre Dame, London

    EDM searches,

    a worldwide perspective

  • Why is there more matter

    than antimatter in the Universe?

    𝜂 =𝑛𝐵−𝑛ഥ𝐵𝑛𝛾

    ≈ 1per billion

    Sakharov’s baryogenesis recipe (1967)

    • Universe out of equilibrium

    • Baryon number not conserved

    • Violation of C and CP symmetry

    69 %

    Dark

    Energy

    5 % Baryons

    26% Dark

    matter

  • Rotation of the spin in an external E field

    𝐻 = − 𝑑 Ԧ𝜎 ⋅ 𝐸The EDM operator must be

    aligned with the spin for a

    simple spin ½ system

    ℏ𝜔 = 2𝑑𝐸

    spin up

    spin down

  • Violation of time reversal

    >> PLAY >>

  • 5/30

    → 𝐻 = 𝑑 ෝ𝝈𝑬

    Electric dipoles & CP symmetry

    𝑑𝑛 < 3 × 10−26 𝑒 cm (Grenoble, 2006)

    𝑑𝑒 < 1 × 10−29 𝑒 cm (Harvard, 2018)

    EDM = CP-violating fermion-photon coupling

    -imaginary part of the diagram-

    generated by radiative corrections

    ℒ = −𝑖𝑑

    2ҧ𝑓𝜎𝜇𝜈𝛾5𝑓 𝐹

    𝜇𝜈

    EDMs: indirect probe of physics at distance 10−26 cm

    LHC: direct probe at large distance 10−17 cm

  • 6/30

    Sources of EDMs in the SM and BSM

    CKM contribution to the quark

    EDM vanishes at two loops…

    The QCD contribution 𝛼

    8𝜋𝜃 𝐺𝜇𝜈 ෪𝐺𝜇𝜈

    Generates a potentially enormous EDM

    𝑑𝑛 ≈ 𝜃 × 10−16 𝑒 cm

    → 𝜃 < 10−10

    « Strong CP problem »

    Prediction: 𝑑𝑛 ≈ 10−33𝑒 cm

    Kobayashi-Maskawa

    background negligible

    Ellis, Ferrara, Nanopoulos, PLB 114 (1982).EDM induced by soft mass terms for squarksand gluinos

    𝑑𝑛 ≈ 𝑒𝛼

    4𝜋

    𝑚𝑞

    𝑀𝐶𝑃𝑉2 ≈

    1 TeV

    𝑀𝐶𝑃𝑉

    2

    ×10−25 𝑒 cm

    « SUSY CP problem »

    MSSM contains ~40 CP violating imaginary parameters…

  • 7/30

    EDMs beyond the SM: modified Higgs couplings

    Barr, Zee, PRL 65 (1990)

    Modified Higgs-fermion Yukawa coupling: ℒ = −𝑦𝑓

    2𝜅𝑓 ҧ𝑓𝑓ℎ + 𝑖 ǁ𝜅𝑓 ҧ𝑓𝛾5𝑓ℎ

    CP violating

    Brod, Haich, Zupan, 1310.1385Brod, Stamou, 1810.12303Brod, Skodras, 1811.05480

    0,001

    0,01

    0,1

    1

    10

    d u s c b t

    90% C.L. limits from eEDM

    90% C.L. limits from nEDM

    Generates EDM at 2 loops ǁ𝜅𝑓

  • 8/30

    Take home messages1. Great puzzle: Baryogenesis still unexplained. CP-violation

    in the standard electroweak theory fails to explain the

    observed baryon asymmetry of the Universe.

    2. Great sensitivity: EDMs are very sensitive probes of CP

    violation beyond the SM because

    (i) New physics at the TeV scale (and beyond) predicts

    generically sizable EDMs

    (ii) CKM contribution to EDMs undetectably small

    3. Complementarity: Importance of measuring the EDMs in

    different systems (neutron, atoms, muons…) to cover the

    many different possible fundamental sources of CP violation

  • 9/30

    Basics of EDM measurement

    𝑓 ↑↑ − 𝑓 ↑↓ = −2

    𝜋ℏ𝑑 𝐸

    2𝜋𝑓 =2𝜇

    ℏ𝐵 ±

    2𝑑

    ℏ|𝐸|

    Easy!

    The trick: measure frequencies** Only if you can’t, try something else

  • 10/30

    Basics of EDM measurement

    2𝜋𝑓 =2𝜇

    ℏ𝐵 ±

    2𝑑

    ℏ|𝐸|

    Easy!

    Larmor frequency (neutron)

    𝑓 = 30 Hz @ 𝐵 = 1 μTIf 𝑑 = 10−27 𝑒 cm and 𝐸 = 15 kV/cmThe spin will make one full turn in a time𝜋ℏ

    𝑑𝐸= 1.4 × 108 s = 𝟒 𝐲𝐞𝐚𝐫𝐬

  • 11/30

    Basics of EDM measurement

    2𝜋𝑓 =2𝜇

    ℏ𝐵 ±

    2𝑑

    ℏ|𝐸|

    If 𝑑 = 10−27 𝑒 cm and 𝐸 = 15 kV/cmone full turn in a time𝜋ℏ

    𝑑𝐸= 1.4 × 108 s = 𝟒 𝐲𝐞𝐚𝐫𝐬

    To detect such a minuscule coupling:

    • Long interaction time

    • High intensity/statistics

    • Control the magnetic field

  • Experiments: 1. Neutron EDM

    2. Other EDMs

  • Neutron EDM history

    Dis

    covery

    Pvio

    latio

    n

    Dis

    covery

    CP

    vio

    latio

    n

    First experiment

    by Smith, Purcell and Ramsey

    with a beam of thermal neutrons,

    interrogation time 𝑇 ≈ 1 ms

    Best « beam » experiment in Grenoble

    with slower neutrons,

    interrogation time 𝑇 ≈ 20 ms

    « Modern » experiments with

    ultracold neutrons started.

    interrogation time 𝑇 ≈ 100 s

    13/30

  • 14/30

    Neutrons with energy < 200

    neV, are totally reflected by

    material walls.

    They can be stored in material

    bottles for long times , up to

    15 minutes.

    They are significantly affected

    by gravity.

    Neutron optics, cold and ultracold neutrons

    Thermal neutrons, E=25 meV

    Cold neutrons, E

  • Best limit: 𝑑𝑛 < 3 × 10−26 𝑒 cm

    Baker et al, PRL (2006); Pendlebury et al, PRD (2015)

    State of

    the art

    Apparatus installed at

    the ILL reactor

    Grenoble (~1980-2009)

  • History of the single-chamber nEDM apparatus

    1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

    Move of the apparatus at

    Paul Scherrer Institute (PSI)

    ILL data production PSI data

    Dismantling nEDM

    Installing n2EDM

    UCN source startup

    & nEDM upgrade

    16/30

  • 17/30

    UCN source at the

    Paul Scherrer Institute

    600 MeV, 2.2 mA

    pulsed UCN source

    One kick per 5 min

    online since 2011

  • 18/30

    Scheme of the

    apparatus at

    PSI during EDM

    data-taking

    2015-2016

    SWITCH

    Magnetized iron analyser

    5T polarizer(SC magnet)

    UCN source

    High voltage, E = ± Τ132 kV 12 cm

    Adiabatic Spin Flipper

    4 layers mu-metal shield

  • Ramsey’s method

    Statistical sensitivity: 𝜎𝑑𝑛 =ℏ

    2 𝛼 𝐸 𝑇 𝑁

    𝑇 = 180s

    19/30

  • 20/35

    Typical measurement sequence at PSI, 1 cycle every 5 minutes

    +1

    32

    kV

    Black:

    uncorrected

    neutron

    frequency

    Green: corrected

    with the mercury

    co-magnetometer,

    compensates for

    the residual

    magnetic field

    fluctuations

    -1

    32

    kV

    + - + -

  • The nEDM collaborationOur collaboration [8 countries, 16 labs, 10 PhD students]

    just finished nEDM.

    The results is 𝑑𝑛 = 𝑋 ± 1.1stat × 10−26 𝑒 cm … still blinded …

    We now start assembling n2EDM aiming at an improved

    sensitivity by an order of magnitude.

    21/30

  • The n2EDM project

    22/30

    The collossal magnetic shield (6 mumetal layers,

    5 × 5 × 5 m3) begins its commissionning phase. Internal parts are under construction or advanced

    design phase

    Will be operational in 2 years

    A large double-chamber

    UCN apparatus at room

    temperature

  • The nEDM competition

    23/35

    Place Neutron source Concept Stage/Readiness

    SNS Spallation + UCN production in situ

    Cryogenic double chamber with helium comagnetometers

    « large scale integration » phase

    PSI Spallation + sD2 UCN source

    n2EDM: double Ramsey chamber with mercury comagnetometers

    Source running, experiment under construction

    LANL Spallation + sD2 UCN source

    double Ramsey chamber with mercury comagnetometers

    Source running, experiment in design phase

    TRIUMF Spallation + superfluid He UCN source

    double Ramsey chamber Source under construction, experiment in conceptual phase

    ILL Reactor +superfluid He UCN source

    panEDM: double Ramsey chamber, no comagnetometers

    Source and experiment under construction

    PNPI WWR-M reactor +inpile superfluid He UCN source

    Getting a really high density of UCNs Source under construction

    ESS Spallation +Cold neutron beam

    100m double beam + time of flight Demonstration phase, small prototype operational @ ILL

    Room temperature UCN experiments aiming at a precision of ≈ 𝟏 × 𝟏𝟎−𝟐𝟕𝒆 𝐜𝐦

  • nEDM competition: superfluid concept

    24/30

    Place Neutron source Concept Stage/Readiness

    SNS Spallation + UCN production in situ

    Cryogenic double chamber with heliumcomagnetometers

    « large scale integration » phase

    Science data taking to start in 2023

    Moon landing in 2024

    Simulated signal

    Oscillates at fn − f3

    Golub-Lamoreaux concept:

    • Aiming at a precision of 𝓞(𝟏𝟎−𝟐𝟖 𝒆 𝐜𝐦)• In-situ UCN production in superfluid helium-4 @ 0.5K

    • Precession of polarized neutrons and helium-3 in the cells

    • Measure the scintillation light of 3He 𝑛, 𝑝 𝑡 which is spin-dependent

  • 2. Other EDMs

    1. Diamagnetic atoms

    2. Paramagnetic atoms and polar molecules

    3. Charged particles: proton, deuton, muon

    4. Other I will not talk about • Heavy baryons @ LHC

    • Tau @ super tau charm factory

  • Very stringent EDM limits of diamagnetic atoms with

    nuclear spin ½

    • Mercury-199: atom-light interaction permits super-

    precise monitoring of the spin precession

    • Xenon-129: very long interaction times (many hours)

    Due to electron shielding, nuclear EDMs do not

    generate atomic EDMs.

    Instead, atomic EDMs could be induced by

    • T-violating e-N interactions

    • A T-odd nuclear deformation (Schiff moment)

    → generating an E field inside the nucleus

    → pulling the s electrons.

    → atomic EDM

    T-violating N-N interactions or nucleon EDM generate a

    nuclear Schiff moment, the effect is larger in heavy

    nuclei, and enhanced in octupole-deformed nuclei like

    radium-225. 26/30

    EDMs of diamagnetic atoms

  • 27/30

    EDMs of paramagnetic systems

    (Cs, Tl, YbF, HfF+, ThO) sensitive to

    • T-violating e-N interactions

    • electron EDM

    Spectacular recent results with ThO @ Yale

    Prospects to go to sensitivity of 𝓞(𝟏𝟎−𝟑𝟎𝒆 𝐜𝐦)• Cesium atom reborn

    • Ultracold YbF fountain

    • ThO

    • HfF+

    • BaF

    • Radioactive Francium atoms (larger Z!)

    EDMs of paramagnetic systems

  • 28/30

    EDMs in storage rings: muon, proton, deutonDifferences with “classic” EDM searches:

    • The lovely configuration 𝑬 ∥ 𝑩 does not work to store charged particles!

    • Relativistic motional fields 𝐸 × Ԧ𝑣 and

    𝐵 × Ԧ𝑣 are not small.

    Spin precession in the

    rotating frame given by

    the BMT equation

    𝜔 =𝑞

    𝑚𝑎𝐵 − 𝑎 +

    1

    1 − 𝛾2Ԧ𝑣 × 𝐸 + 2𝑑 Ԧ𝑣 × 𝐵 + 𝐸

    Term due to magnetic dipole.

    Can be set to ~0 by choosing 𝐵, 𝐸, Ԧ𝑣« frozen spin »

    Term due to electric dipole.

    Makes spin go « out of plane »

    Prospects:

    • Muon EDM @ JPARC 𝒪 10−21 𝑒 cm• Frozen spin muon EDM @ PSI 𝒪 10−24 𝑒 cm• Frozen spin proton & deuton EDM 𝒪 10−29 𝑒 cm

  • EDMs: the worldviewNeutrons (~200 ppl)

    • Beam EDM @ Berne

    • LANL EDM @ Los Alamos

    • n2EDM @ PSI

    • nEDM @ SNS

    • panEDM @ ILL

    • PNPI/FTI/ILL

    • TUCAN @ TRIUMF

    Diamagnetic atoms

    (~70 ppl)

    • Hg @ Bonn

    • Ra @ Argonne

    • Xe @ Heidelberg

    • Xe @ PTB

    • Xe @ Rikken

    Paramagnetic systems

    (~80 ppl)

    ▪ Cs @ Penn State

    ▪ Fr @ Rikken

    ▪ BaF @ Nikhef

    ▪ BaF @ Toronto

    ▪ HfF+ @ JILA

    ▪ ThO @ Yale

    ▪ YbF @ London

    www.psi.ch/en/nedm/edms-world-wide

    Storage rings (~400 ppl)

    ▪ srEDM/JEDI

    ▪ muEDM @ PSI

    ▪ (g-2) @ Fermilab

    ▪ (g-2) @ JPARC

  • Concluding remarks

    30/30

    Interdisciplinary field

    • Motivations from cosmology and particle physics

    • Techniques from nuclear and atomic physics

    Many experiments/projects

    • Prioritize? Not a good idea…

    • Towards a combined global effort?

    Makes sense for nEDM and pEDM at the horizon 2030

    Exciting future

    Experiments are getting harder and harder, but they are now pushing

    the frontier of BSM CP violation beyond the electroweak scale.

    Ambition: learn whether or not the matter-antimatter asymmetry was

    generated during the Electroweak Phase transition!

  • thank you, the rest are backup slides

  • About 10 Big neutron sources available for

    fundamental physics in the world

    SNS Oak Ridge

    1.4 MW beam

    PSI Switzerland

    1.5 MW proton beam

    Los Alamos

    TRIUMF

    Vancouver

    J-PARC

    PNPI

    ILL Grenoble

    58 MW reactor

    NIST NCNR

    20 MW reactor

    Number of operational

    nuclear reactors in the

    world, according to IAEA:

    227 research reactors

    453 power reactors

    TRIGA Mainz

    pulsed reactor

  • T = 300 GeV

    T ≃ 100 GeV

    T = 20 GeV

    symmetric phase𝝓 = 𝟎

    boiling

    broken phase𝝓 ≠ 𝟎

    Electroweak baryogenesis?

    33

    1015 GeVInflation ends?

    100 GeVElectroweak

    transition

    1 MeV

    1 eVDecoupling

    of CMB

    1 meVToday

    Sakharov’s Baryogenesis

    recipe (1967)

    • Baryon number not

    conserved

    • Universe out of equilibrium

    • Violation of CP symmetry

    >> EDMs

    Current EDM bound

    constrains many

    scenarios of BSM

    electroweak baryogenesis

  • Energy scale ladder

    34/35

  • 35/22

    Free precession in

    E and B fields ...

    C: Apply RF pulse

    π/2 spin-flip...A: spin polarizer

    C’ :Second RF pulse

    A’: spin

    analyzer

    D: counter

    First EDM experiment with a neutron beam

    Smith, Purcell and Ramsey, Phys. Rev. 108, 120 (1957)

    𝑑𝑛 = −0.1 ± 2.4 × 10−20 𝑒 cm

    Vary the RF frequency

    and measure the resonance

    curve to extract 𝑓𝐿. Do it forparallel and antiparallel E

    and B fields.

    Statistical sensitivity:

    𝜎𝑑𝑛 =ℏ

    2 𝛼 𝐸 𝑇 𝑁

    𝑇 ≈ 1 ms

  • Storing Ultracold neutrons in the nEDM apparatus

  • The co-magnetometer problem: vxE/c2

    𝑑𝑛←Hgfalse =

    ℏ|𝛾𝑛𝛾Hg|

    2𝑐2න0

    𝑑𝑡 cos𝜔𝑡 𝑩𝒙 𝟎 ሶ𝒙 𝒕 + 𝑩𝒚 𝟎 ሶ𝒚 𝒕

    Simulation, Hg atoms in nEDM Ø47cm

    Frequency shift from a transverse

    magnetic noise B (Redfield theory)𝛿𝑓 =

    𝛾2

    4𝜋න0

    𝑑𝜏 Im 𝑒−𝑖𝜔𝜏 𝐵 0 𝐵∗(𝜏)

    Linear in E field frequency shift:

  • Magic field 𝑑𝑛←Hgfalse (𝝎) =ℏ|𝛾𝑛𝛾Hg|

    2𝑐2න0

    𝑑𝑡 cos𝝎𝑡 𝐵𝑥 0 ሶ𝑥 𝑡 + 𝐵𝑦 0 ሶ𝑦 𝑡