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