Transcript Future electron EDM measurements using YbF

Future electron EDM measurements
using YbF
Ben Sauer
Predicted values for the electron edm de (e.cm)
Recent electron EDM measurements
10-22
10-24
10-26
10-28
MSSM
f~1
Multi
Left Higgs
Right
MSSM
f ~ a/p
10-30
YbF experiment (2011)
de < 1 x 10-27 e.cm (90% c.l.)
de < 8.7 x 10-29 e.cm (90% c.l.)
ThO* experiment (2013)
10-32
10-34
10-36
Tl experiment (2002)
de < 1.6 x 10-27 e.cm (90% c.l.)
Standard Model
An EDM experiment
E
Polarize
Precess
time T
Analyze
Sensitivity of an EDM experiment

Uncertainty:  d 
ET 2CN
size of E field
coherence time
polarization
contrast
number of
molecules
Why polar molecules?
de 
E
electric field
Interaction energy
-de E•
Analogous to magnetic dipole
interaction -gem B. but
violates P&T
Factor  includes both
relativistic interaction Z3,
system containing and polarization
electron
© Imperial College London
15
10
15 GV/cm
(2011)
Parpia
Quiney
Kozlov
Titov
5
18 GV/cm
Effective Field |E| (GV/cm)
YbF: really large internal field
5
10
15
20
25
Applied Electric Field (kV/cm)
© Imperial College London
30
ThO*: huge internal field
Effective field Eeff in YbF is 26 GV/cm
when molecule is fully polarized
For ThO* Eeff is about 84 GV/cm (factor of
3.2 more sensitive)
3
Mostly relativistic:
 Z Th 

  2.1
 Z Yb 
(also depends on structure)
ThO* can be fully polarized!
Comparing some atomic and
molecular systems
• YbF, 2011: |Eeff|= 14.5 GV/cm ( = 0.56)
|de|<1.0 x 10-27 e.cm (90% c.l.)
• Tl, 2002: |Eeff|= 72 MV/cm (Eeff = -582 Eapplied)
|de|<1.6 x 10-27 e.cm (90% c.l.)
• PbO*, 2013: |Eeff|= 25 GV/cm
|de|<1.7 x 10-26 e.cm (90% c.l.)
• Eu0.5Ba0.5TiO3, 2012:
|de|<6 x 10-25 e.cm (90% c.l.)
• ThO*: |Eeff| = 84 GV/cm (factor of 6 on 2011 YbF)
|de|<8.7 x 10-29 e.cm (90% c.l.)
Upgrades since 2011
3rd layer of magnetic shield
(less noise)
Longer inner magnetic shield
(reduce end effects)
Longer interaction region
Separate rf, high-voltage plates
(reduce end effects, higher voltage, less leakage)
1kW/1ms rf pulses
(reduce gradient effects from both movement and linewidth)
In total, a factor of 3 in sensitivity
Our plans for YbF
• More molecules
- increase beam intensity
- better detection
• Slower molecules
Made possible by new technology
- solid state lasers
- buffer gas beam sources
© Jony Hudson
A rough guide to YbF
A 2P½ (v=0, N=0)
552nm

mF = -1

mF = 0
mF = +1
170MHz
mF = 0
Page 12
F=0
F=1
X 2S+ (v=0, N=0)
YbF eEDM measurement
E, B
Precess
time T
Polarize
1
 
2


1 i
e   e  i 
2
Analyze

Measure population
in F = 0
N cos 2  
F=0 population
Signal vs. magnetic phase
  gm B B  d e E T 
Signal  cos f   cos 

Page 14
© Jony
Hudson


2
2
F=1
F=0
More molecules: Initial pumping
Use cycling transition to optically pump
molecules into ground rotational state.
F=0, 1 A2P1/2 (v=0, J=1/2)
(-)
F=2+
F=1
F=3
F=2-
N=2 (J=3/2, 5/2) (+)
F=1+
F=2
F=0
F=1-
N=1 (-)
N=0 (+)
F=1
F=0
Scheme increases
population by a
factor of 7,
sensitivity by 2.6
rf mixing (~100 MHz)
Microwave mixing (14 GHz)
Optical pumping (N=2 rotational state)
More molecules: Better detection
Fluorescence detection is only about 0.7% efficient
Probe laser beam
More molecules: make them cycle
F=0, 1 A2P1/2 (v=0, J=1/2)
(-)
F=2+
F=1
F=3
F=2-
N=2 (J=3/2) (+)
F=1+
F=2
F=0
F=1-
N=1 (-)
N=0 (+)
F=1
F=0
Molecules cycle until they escape to v=1 vibrational state (14 photons/molecule)
A flaw: measuring the eEDM
Detector count rate
F=0
F=1
F = 0 and F = 1 are the two output ports of
the interferometer
B0
-B0
Applied magnetic field
Page 18
Shelve population in N=1
F=0, 1 A2P1/2 (v=0, J=1/2)
(-)
F=2+
F=1
F=3
F=2-
N=2 (J=3/2) (+)
F=1+
F=2
F=0
F=1-
N=1 (-)
N=0 (+)
F=1
F=0
Sensitivity gain of 5
High fidelity shelving
The problem is the YbF beam is larger than l at 14 GHz.
Cross section of simulated parallel plate
transmission line.
plate
plate
microwaves
in
uniform
(integrated) field
High fidelity shelving
Transition probability over cross section of YbF beam
Average transition probability N=0  N=1 over YbF beam >98%
Slow source of YbF
4K copper cell
4K helium flow
Nick Bulleid (PhD thesis, 2013)
YbF formed by laser ablation, cools to 4K,
forward velocity is 150 m/s. Flux is similar
to current beam (5x109 YbF /str/pulse)
(20 sccm)
time after ablation (ms)
YbF velocity (m/s)
YbF signal
Slow source of YbF
time after ablation (ms)
2011 supersonic beam had forward velocity of 600 m/s
“Traditional” YbF eEDM
Compared to 2011 measurement:
•
•
•
•
Factor 3 for longer plates
Factor 2 for N=2 population pumping
Factor 5 for cycling detection
Factor 4 for slower beam
• Two orders of magnitude improvement is
underway.
• We have a lot of experience and a fairly
sophisticated data analysis scheme, so
should be able to control systematic effects.
Is there more?
YbF eEDM experiment takes place in the
ground state, so why not coherence times of
1s?
Building the YbF fountain
Fantastically inefficient: 10-8 from cell to
detector. But T = 300ms, so 60h of data
gives d = 3x10-31 e.cm!
The YbF team
Mike Tarbutt
Jony Hudson Joe Smallman
Isabel Rabey
B.E.S.
Jack Devlin
YbF fountain:
James Bumby
James Almond
Jongseok Lim
Noah Fitch
Ed Hinds
Everything
clear?