Download Precision atomic physics tests of P, CP, and CPT symmetries
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Download Download Precision atomic physics tests of P, CP, and CPT symmetries...
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Fundamental Symmetry Tests with Atoms Michael Romalis Princeton University
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1. Atomic Parity Violation
2. Limits on CP violation from Electric Dipole Moments
3. Tests of CPT and Lorentz symmetries
Atomic parity violation Parity transformation:
ri ri
Electromagnetic forces in an atom conserve parity [Hatomic, P]=0 Atomic stationary states are eigenstates of Parity But weak interactions maximally violate Parity! Electromagnetic
Weak
Tiny virtual contribution of Z-boson exchange can be measured!
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Atomic Parity Violation Experiments Early work: M.-A. Bouchiat, C. Bouchiat (Paris) Sandars (Oxford) Khriplovich, Barkov, Zolotorev (Novosibirsk) Fortson (Seattle)
Current Best Measurement – Wieman (Bolder, 1999) Parity mixing on M1 transition 6S1/2 7S1/2 transition in Cs
Experimental accuracy on PV amplitude EPV:
0.35%
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Relation to Standard Model Parameters Exchange of virtual Z0 boson: HW
GF e 5e C1u u u C1d d d ... 2
GF H [ N Z (1 4 sin W )] 5 (r) 8 e W
2
Weak charge Qw
Nuclear (neutron) distribution
EPV k PV QW
Best Atomic Calculation in Cs: 0.27% error - Derevianko (Reno, 2009) Phys. Rev. Lett. 102, 181601 (2009)
Parity violation in Yb Parity violation is enhanced 100 times in Yb because of close opposite-parity states (DeMille, 1995) Atomic calculations will not be as accurate, but one can compare a string of isotopes and measure the anapole moment First observation by Budker with 14 % accuracy (2009) The experiment is improving, needs to reach ~ 1%
K. Tsigutkin et al, Phys. Rev. Lett. 103, 071601 (2009)
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Impact on Electroweak Physics
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T and CP violation by a permanent EDM Time Reversal:
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t–t I –I
dd
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d –d 0 d =dI I d 0 violation of time reversal symmetry
Vector:
CPT theorem also implies violation of CP symmetry
EDM T violation CP violation
• Relativistic form of interaction: L = d E = – i d 5F 2
Requires a complex phase
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EDM Searches Nuclear
High Energy
Theory
Nuclear
Atomic
Neutron n
Experiments Molecular
Atomic Diamagnetic Atoms Hg, Xe, Rn
Paramagnetic Atoms Tl,Cs, Fr
Molecules PbO, YbF, TlF
Atomic Theory
Atomic Theory
Atomic Theory
Nuclear Theory QCD
QCD
Quark EDM
Quark Chromo-EDM
Electron EDM
Fundamental Theory Supersymmetry, Strings
Discovery potential of EDMs
In SM the only source of CP violation is a phase in CKM matrix
The EDMs are extremely small, require high-order diagrams with all 3 generations of quarks
Almost any extension of the Standard Model contains additional CPviolating phases that generally produce large EDMs.
Raw energy sensitivity: d ~
em , 10 – 27 e cm 2
=100 TeV
Current experiments are already sensitive enough to constrain EDMs from Supersymmetry by a factor of 100 or more
Baryogenesis scenarios:
Electroweak baryogenesis: EDMs around the corner, somewhat unfavorable based on existing constraints
Leptogenesis: No observable EDMs
Other (GUT scale, CPT violation): No observable EDMs
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Experimental Detection of an EDM
• Measure spin-precession frequencies B
E
d w1
w1 =
B
2 B+ 2dE h
E
H = – B – d E
d w1 w2 = 2 B 2dE h
w1 – w2 = 4dE h
• Statistical Sensitivity: Single atom with coherence time t:
dw = t1
h N uncorrelated atoms measured for time T >> t: d d =
1
2E 2tTN
Search for EDM of the neutron
Historically, nEDM experiments eliminated many proposals for CP violation
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ILL neutron EDM Experiment n, 199Hg
40 mHz
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Recent nEDM result Complicated effects of motional magnetic field Bm = E v/c Random motion results in persistent rotating magnetic field Dependance on field gradient dBz/dz dBr/dr r
V
V
Rotating field causes frequency shift E and B0 into page
dBz/dz
dn = 0.61.5(stat)0.8(syst) 10-26 ecm |dn| < 3.0 10-26 ecm (90% CL)
Factor of 2 improvement dBz/dz
C.A. Baker et al Phys. Rev. Lett. 97, 131801 (2006)
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Cryogenic nEDM experiments Superthermal production in superfluid 4He N increased by 100 – 10000 He-4 good isolator, low temperature E increased by 5 Superconducting magnetic shields SQUID magnetometers
1 m
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Electron EDM Electron has a finite charge, cannot be at rest in an electric field For purely electrostatic interactions
F = eE = 0 E = 0 — Schiff shielding, 1963
Can be circumvented by magnetic interactions, extended nucleus
F = eE+B = 0, E 0 Enhanced in heavy atoms: 3 2 d a d e Z Strong spin-orbit magnetic interaction Large Nuclear Coulomb field Relativistic electrons near the nucleus
Thallium: d Tl = – (585 ± 50) d e
Sandars, 1965
Cs: 114,
Fr: 1150
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Berkeley Tl EDM Experiment Tl (~700 C) Tl detectors
Mixing chamber
Beam stop
Light pipe photodiodes
Na (~350 C) 378 nm laser beams
70 Hz
Analyzer
Na detectors
590 nm laser beams
RF 2 Collimating slits
E-field (120 kV/cm) 1m
Atomic beams
B Collimating slits
RF 1
590 nm laser beams
• Na atoms used as a co-magnetometer
de = (6.9 7.4)10-28 ecm |de| < 1.610-27 ecm (90% C.L.)
Na detectors State Selector
Tl detectors
378 nm laser beams
Beam stop Tl (~700 C)
Mixing chamber
Na (~350 C)
B. Regan, E. Commins, C. Schmidt, D. DeMille, Phys. Rev. Lett. 88, 071805 (2002)
YbF Experiment Polarized polar molecules have very high internal electric field It is hard to generate paramagnetic molecules
New Result !!! de= (−2.4 ± 5.7 ± 1.5) × 10−28e cm Only 20% better than Thallium J. J. Hudson, D. M. Kara, I. J. Smallman, B. E. Sauer, M. R. Tarbutt, E. A. Hinds, Nature 473, 493, (2011)
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199Hg
EDM Experiment Solid-state Quadrupled UV laser
100,000 hours of operation High purity non-magnetic vessel
Hg Vapor cells
All materials tested with SQUID Spin coherence time: 300 sec Electrical Resistance: 21016 W
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Recent improvements in 199Hg Experiment Use four 199Hg cells instead of two to reduce magnetic field noise and have better systematic checks
inner cells
w1 w2 w3
E E
outer cells
w4 Magnetic Gradient Noise Cancellation S = w2 w3 1/3 w1 w4 Leakage Current Diagnostic L = w2 w3 w1 w4 Larger signal due to cell improvements Frequency uncertainty 0.1 nHz
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New
199Hg
EDM Result
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About 1 year of data Changed all components of the system:
d(199Hg) = (0.49±1.29stat±0.76syst)×10−29 e cm W. C. Griffith, M. D. 199 −29 |d( Hg)| < 3.1×10 e cm (95% C.L.) Swallows, T. H. Loftus, M. V. Romalis, B. R. Factor of 7 improvement Heckel, E. N. Fortson Phys. Rev. Lett. 102, 101601 (2009)
Continued work on
199Hg
Still a factor of 10-20 away from shot noise limit Limited by light shift noise, magnetic shield noise Need to find more precisely path of leakage currents Practical cell fabrication issues
Steady improvement – factor of 3-5 improvement in ~3 years
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Interpretation of nuclear EDM Limits No atomic EDM due to EDM of the nucleus Schiff’s Theorem Electrons screen applied electric field d(Hg) is due to finite nuclear size nuclear Schiff moment S Difference between mean square radius of the charge distribution and electric dipole moment distribution 2 x 2 x 5 r 2 3 S dx x 5 3
x ch
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Recent work by Haxton, Flambaum on form of Schiff moment operator
Schiff moment induces parity mixing of atomic states, giving an atomic EDM:
da = RA S
RA - from atomic wavefunction calculations, uncertainty 50% B. P. Das et al, V. Dzuba et al.
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Interpretation of nuclear EDMs The Schiff moment is induced by CP nucleon-nucleon interaction:
Due to coherent interactions between the valence nucleon and the core
S RN gNN
Large uncertainties due to collective effects
gNN
n
p
Engel, Flambaum
CP-odd pion exchange dominated by chromo-EDMs of quarks
g
Factor of 2 uncertainty in overall coefficient due to approximate cancellation q (1)
gNN
~ ~ RQCD ( du dd )
Other effects: nucleon EDMs, electron EDM, CPviolating nuclear-electron exchange
q Pospelov et al.
Sen’kov Oshima Flambaum
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Jon Engel calculations for 199Hg(2010) isovector
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Octupole Enhancement I
1| 1|/2
|+ DE
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| |/2
P, T
| |/2
1| 1|/2
|
V PT
Slab ~ e Z A2/3 2 32/DE
Sintr ~ eZA23
DE
~
3 A1 / 3 DE
2 , 3 ~0.1
Haxton & Henley; Auerbach, Flambaum & Spevak; Hayes, Friar & Engel; Dobaczewski & Engel 223Rn
t1/2 I Deth (keV) DEexp (keV) 105 S (efm3) 1028 dA (e cm)
23.2 m 7/2 37 -1000 2000
223Ra
11.4 d 3/2 170 50.2 400 2700
225Ra
14.9 d 1/2 47 55.2 300 2100
223Fr
22 m 3/2 75 160.5 500 2800
225Ac
10.0 d 3/2 49 40.1 900
229Pa
1.5 d 5/2 5 0.22 12000
199Hg
129Xe
1/2
1/2
-1.4 -5.6
1.75 0.8
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Oven: 225Ra
EDM measurement with 225Ra
Transverse cooling
Zeeman Slower
Statistical uncertainty:
Magneto-optical trap
100 days 10 days 100 kV/cm
100 10 s
1064
10%
-26 e cm Phase II dd = 3 x 10-28
• 225Ra / 199Hg enhance factor ~ 1,000 • dd(199Hg) = 1.5 x 10-29 e cm
EDM measurement
Optical dipole trap
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Limits on EDMs of fundamental particles EDM: e d – d < 610 – 27 e cm d u • Neutron EDM: e(d d +0.5d u)+1.3d d –0.32d u 1/2 Quadrupole energy shift due to angular momentum of the valence nucleon:
EQ ~ (c11 c22 2c33 ) p x2 p y2 2 p z2
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px2 p y2 2 pz2 0 pn Previously has been searched for in two experiments using 201Hg and 21Ne with sensitivity of about 0.5 Hz Bounds on neutron cn
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