Transcript Slide 1

FrPNC @ TRIUMF
Atomic Parity Violation in
Francium
Seth Aubin
College of William and Mary
PANIC 2011 Conference, MIT
FrPNC collaboration
S. Aubin (College of William and Mary)
J. A. Behr, K. P. Jackson, M. R. Pearson (TRIUMF)
V. V. Flambaum (U. of New South Wales, Australia)
E. Gomez (U. Autonoma de San Luis Potosi, Mexico)
G. Gwinner, R. Collister (U. of Manitoba)
D. Melconian (Texas A&M)
L. A. Orozco, J. Zhang (U. of Maryland at College Park)
G. D. Sprouse (SUNY Stony Brook)
Y. Zhao (Shanxi U., China)
Funding
Atomic Parity Violation: Basic Processes
e-
e-
e-

e-
e-
e-

Z0
W,Z0 exchange
in nucleus
N
N
Standard
Electromagnetic
Interaction
(parity conserving)
N
N
N
N
Z0 exchange
Intra-nuclear PNC
Electron-Nucleon PNC
Anapole moment
(nuclear spin-independent)
(nuclear spin-dependent)
Atomic Parity Violation: Basic Processes
e-
e-
e-

e-
e-
e-

Z0
W,Z0 exchange
in nucleus
N
N
Standard
Electromagnetic
Interaction
(parity conserving)
N
N
N
N
Z0 exchange
Intra-nuclear PNC
Electron-Nucleon PNC
Anapole moment
(nuclear spin-independent)
(nuclear spin-dependent)
Motivation 1:
Nuclear Spin-Independent PNC
e-
e-
Ae
The Hamiltonian for this interaction:
(infinitely heavy nucleon approximation)
Z0
H PNC , nsi

G

1  5  ( r )
2
G = Fermi constant = 10-5/mp2
VN
N
1, p  12 1  4 sin 2 W   0.04
Neutron: 1,n  0.5
Proton:
N
Z0 exchange
Electron-Nucleon PNC
(nuclear spin-independent)
[Standard Model values for 1, (p,n)]
Motivation 1:
Nuclear Spin-Independent PNC
e-
e-
Ae
For a nucleus with Z protons
and N neutrons:
Z0
Qweak = weak charge of nucleus  -N
VN
nucleons
H PNC , nsi

G Qweak

 5  (r )
2 2
= 2(1,p Z + 1,n N)
nucleons
Z0 exchange
Electron-Nucleons PNC
(nuclear spin-independent)

 (r )  nucleon distribution
Motivation 1:
Testing and Probing the Weak Interaction
Parity Violation = Unique Probe of Weak Interaction
Atomic PNC (APV) experiments test and constrain the Standard Model
Motivation 1:
Testing and Probing the Weak Interaction
Parity Violation = Unique Probe of Weak Interaction
Atomic PNC (APV) experiments test and constrain the Standard Model
Weak mixing angle
[figure by G. Gwinner, adapted from Erler et al. Phys. Rev. D 72, 073003 (2005)]
Effective e--quark couplings C1u & C1d
[figure from Young et al., Phys. Rev. Lett. 99, 122003 (2007)]
Atomic PNC
H PNC , nsi

G Qweak

 5  (r )  Parity Odd
2 2
 Electron wavefunction does not have a definite parity !!!

S  S   PNC P
Parity forbidden transitions
become possible (slightly) !!!
P  P   PNC S
 PNC,nsi  Z R ~ 10
3
11
relativistic enhancement factor
(Cs)
Francium advantage:
 PNC ,nsi Fr

 PNC ,nsi Cs 
18
Motivation 2:
Nuclear Spin-Dependent PNC
e-
e-
e-
e-
e-
e-
Ae
Ve

Z0

Z0
W,Z0 exchange
in nucleus
N
N
Intra-nuclear PNC
Anapole moment
N
AN
N
Z0 exchange
Electron-Nucleon PNC
(vector) (axial)
N
VN
N
Hyperfine Interaction
+
NSI - Z0 exchange
(nuclear spin-dependent)
What’s an Anapole Moment ?
e-
e-
Answer:
Electromagnetic moment produced by a
toroidal current.

W,Z0 exchange
in nucleus
N
N
 Time-reversal conserving.
 PNC toroidal current.
 Localized moment, contact interaction.
[A. Weis, U. Fribourg (2003)]
Motivation 2:
Nuclear Anapole Moment
e-
e-
For heavy atoms, the anapole moment term
dominates.
H PNC ,nsd

W,Z0 exchange
in nucleus
N
N
Anapole moment
  
G
K

 anapole ( p ,n ) I    (r )
2 I I  1) 
Motivation 2:
Nuclear Anapole Moment
e-
e-
For heavy atoms, the anapole moment term
dominates.
H PNC ,nsd

W,Z0 exchange
  
G
K

 anapole ( p ,n ) I    (r )
2 I I  1) 
 anapole ( p,n)
 p,n
9
2/3
Z  N 
 g p ,n
~
10
mp r0
in nucleus
N
N
Anapole moment
K  I  1 / 2  1
I  nuclear spin
I 1 / 2  l
l  valencenucleonorbital
angularm om entum
  1 / 137
  nucleonm agneticm om ent
~
r0 1.2 fm  nucleonradius
Motivation 2:
Nuclear Anapole Moment
e-
e-
For heavy atoms, the anapole moment term
dominates.
H PNC ,nsd

W,Z0 exchange
in nucleus
N
N
Anapole moment
  
G
K

 anapole ( p ,n ) I    (r )
2 I I  1) 
 anapole ( p,n)
 p,n
9
2/3
Z  N 
 g p ,n
~
10
mp r0
g p ~ 4 and 0.2  gn  1 characterize
the nucleon-nucleus weak potential.
K  I  1 / 2  1
I  nuclear spin
I 1 / 2  l
l  valencenucleonorbital
angularm om entum
  1 / 137
  nucleonm agneticm om ent
~
r0 1.2 fm  nucleonradius
Motivation 2:
Isovector & Isoscalar Nucleon Couplings
Cs anapole (Boulder) and low-energy nuclear PNC
measurements produce conflicting constraints on
weak meson-nucleon couplings.
(Desplanques, Donoghue, and Holstein model)
Need to understand
nuclear structure better.
Measure anapole in a string
of Fr isotopes
[Haxton et al., Phys. Rev. C 65, 045502 (2002) and
6Li(n,) from Vesna Phys. Rev. C 77, 035501 (2008)]
Motivation 2:
Isovector & Isoscalar Nucleon Couplings
Cs anapole (Boulder) and low-energy nuclear PNC
measurements produce conflicting constraints on
weak meson-nucleon couplings.
(Desplanques, Donoghue, and Holstein model)
[Behr and Gwinner, J. Phys. G 36,
033101 (2009)]
[Haxton et al., Phys. Rev. C 65, 045502 (2002) and
6Li(n,) from Vesna Phys. Rev. C 77, 035501 (2008)]
Francium isotopes
provide orthogonal
constraints !!!
Francium advantage:
 PNC,anapole Fr
 11
 PNC,anapole Cs 
FrPNC program:
Atomic PNC Experiments in Francium

Fr is the heaviest of the simple (alkali atoms).
 Electronic structure is well understood.
 Particle/nuclear physics can be reliably extracted.
 Fr has large (relatively) PNC mixing.
 PNC ~ 10-10 is still really really small … we’re going to need a lot of Fr.
 Fr does not exist sufficiently in nature.
+
dipole trap
Atomic PNC in Fr (NSI)
EStark
Excitation to continuum
(ionization)
k
506 nm
Fr atoms
(trapped)
506 nm
8S1/2
F’
F

 

 PNC  BDC  k  EStark
1.3 m
1.7 m
7P3/2
7P1/2
506 nm
E1
“forbidden”
BDC

Amplification by Stark Interference
TransitionRate  AStark  APNC
2


 AStark  2 Re AStark APNC  APNC
2
718 nm
817 nm
F’
Statistical Sensitivity:
7S1/2
F
M1 is strongly suppressed.
*
2
Anapole Moment in Fr
New Method: Anapole can be measured by driving a parity forbidden
E1 transition between two hyperfine states with F=1, mF=1.
/2 pulse preparation: the atoms are prepared in a 50/50 superposition
of the initial and final states (equivalent to interference amplification)
before application of the microwave driving E-field.
F ' , mF '
7S1/ 2
M1
E1PNC
F, mF
Anapole Moment in Fr
New Method: Anapole can be measured by driving a parity forbidden
E1 transition between two hyperfine states with F=1, mF=1.
/2 pulse preparation: the atoms are prepared in a 50/50 superposition
of the initial and final states (equivalent to interference amplification)
before application of the microwave driving E-field.
F ' , mF '
7S1/ 2
M1
E1PNC
F, mF




 anapole  BDC  M1 / 2  Emicrowave

Anapole Moment in Fr
New Method: Anapole can be measured by driving a parity forbidden
E1 transition between two hyperfine states with F=1, mF=1.
/2 pulse preparation: the atoms are prepared in a 50/50 superposition
of the initial and final states (equivalent to interference amplification)
before application of the microwave driving E-field.
F ' , mF '
7S1/ 2
M1
E1PNC
F, mF
Signal to  noise ~ 20 Hz 1
for Emicrowave~0.5 kV/cm and 106 atoms.
[E. Gomez et al., Phys. Rev. A 75, 033418 (2007)]




 anapole  BDC  M1 / 2  Emicrowave

Simulating Fr Anapole with Rb
180 ms coherence time in
blue-detuned dipole trap
(/2 pulse with Rb)
[Data by D. Sheng (Orozco Group, U. of Maryland)]
Simulating the PNC Interference
TransitionRate  1 / 2  APNC
2
 1 / 4  APNC cos phase
APNC simulated with 10-4 M1 transition
FrPNC: Current Status
Present: Construction of an on-line, shielded laser laboratory at TRIUMF
with 100 db RF suppression.
Fall 2011: (14 shifts in December)
Installation of high efficiency MOT
(from U. of Maryland).
2012: Physics starts !!!
Hyperfine anomaly (Pearson), 7S-8S M1 (Gwinner),
Anapole (Orozco), optical PNC (Gwinner), …
FrPNC collaboration
S. Aubin (College of William and Mary)
J. A. Behr, K. P. Jackson, M. R. Pearson (TRIUMF)
V. V. Flambaum (U. of New South Wales, Australia)
E. Gomez (U. Autonoma de San Luis Potosi, Mexico)
G. Gwinner, R. Collister (U. of Manitoba)
D. Melconian (Texas A&M)
L. A. Orozco, J. Zhang (U. of Maryland at College Park)
G. D. Sprouse (SUNY Stony Brook)
Y. Zhao (Shanxi U., China)
Funding