Download Precision atomic physics tests of P, CP, and CPT symmetries

January 16, 2018 | Author: Anonymous | Category: , Science, Astronomy, Particle Physics
Share Embed


Short Description

Download Download Precision atomic physics tests of P, CP, and CPT symmetries...

Description

I

Fundamental Symmetry Tests with Atoms Michael Romalis Princeton University

I

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!

I

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%

I

I

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)

I

Impact on Electroweak Physics

I

T and CP violation by a permanent EDM  Time Reversal:

I

t–t I  –I

dd

I

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    5F  2

Requires a complex phase

I

I

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

I

I

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

I

I

ILL neutron EDM Experiment n, 199Hg

40 mHz

I

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 = 0.61.5(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)

I

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

I

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

I

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 ecm |de| < 1.610-27 ecm (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)

I

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: 21016 W

I

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

I

New

199Hg

EDM Result

I

 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

I

I

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  

I E

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.

I

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 gNN

 Large uncertainties due to collective effects

gNN

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)

gNN

~ ~  RQCD ( du  dd )

 Other effects: nucleon EDMs, electron EDM, CPviolating nuclear-electron exchange

q Pospelov et al.

Sen’kov Oshima Flambaum

I

Jon Engel calculations for 199Hg(2010) isovector

I

Octupole Enhancement I

  1| 1|/2

|+ DE

I

  |  |/2

P, T

  |  |/2

  1| 1|/2



|

  V PT  

Slab ~ e Z A2/3 2 32/DE

Sintr ~ eZA23

DE

~

 3 A1 / 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

I

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

I

Limits on EDMs of fundamental particles EDM: e d – d < 610 – 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

I,L

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
View more...

Comments

Copyright © 2017 HUGEPDF Inc.