# Presentation: 514189

## Tabletop probes for TeV physics:the search for electric dipole moments

-   EDMs and new physics
-   how to detect an EDM
-   electron EDM in atoms & molecules
-   the state of the art electron EDM search
-   the next generation
-   our approach:  PbO*

- D. DeMille
*Yale University*
*Physics Department*

- Funding: NSF, Packard, CRDF, NIST, Sloan, Research Corp.

**Review:**
- Fortson, Sandars, & Barr
- Physics Today June 2003

**Notes:**
Get more complete chart of EDM predictions from Yong
Get better group picture

## An EDM Violates P and T

- CPT theorem  T-violation = CP-violation

- Purcell
- Ramsey
- Landau

## T-violation: a window to new physics

- •  CP-violation observed in K- and B-mesons
- 	 T is _***NOT***_ conserved in nature
- K-, B-meson observations consistent with
-     SM/CKM description including O(1) phase 
- 	_***but also***_ consistent w/models containing
-     new sources of T-violation
- •  CP-violation in SM is minimal:
-    SM extensions typically include _***NEW***_ sources of T-violation
- •  Observed baryon asymmetry in universe
-    _***REQUIRES***_ new sources of T-violation

## Virtual exotic particles can generate EDMs

- e

-    = E-field

*X*
- (new heavy particle)

*f’**e**i***

*f*

- Dimensionless
- coupling
- constant

- T-violating
- phase

- “natural” assumptions
*ff’*/ħc  
- sin(**) ~ 1
*m**X** * ~ 100 GeV
- 
- typical e-*EDM~*
*d**e**~****B *
*(****/***)N (me/mX)2 sin()
*d**e** **100-1× *
- current limit!
- (1 vs. 2 loops)

## Electron EDM in various SM extensions

**not renormalizable ******** loop diagrams**

**Experimental limit:**
**|d****e****| < 1.6********10****-27**** e********cm**

| Physics model | |de| |
| --- | --- |
| Standard Model | ~10-41 e·cm |
| Left-right symmetric | 10-26-10-28 e·cm |
| Lepton flavor-changing | 10-26-10-29 e·cm |
| Multi-Higgs | 10-27-10-28 e·cm |
| Technicolor | 10-27-10-29 e·cm |
| Supersymmetry | < 10-25 e·cm |

- B. Regan, E. Commins, C. Schmidt,
- D. DeMille, PRL **88**, 071805 (2002)

*Models assume*
*new physics at ~100 GeV*
*& CP-violating phases ~1*

## Searching for SUSY w/ the electron EDM 

- Implications of current and ongoing electron EDM searches

## Current status of ALL EDM searches

|  | n (ILL,PNPI)  | Hg (Seattle)  | Tl (Berkeley)  |
| --- | --- | --- | --- |
| EDM  | <710-26  | <210-28  | <110-24  |
| dn  | 710-26  | 210-25  |  |
| de  |  | 1510-27  | 1.610-27  |
| QCD  | 410-10  | 210-10  |  |
| q/l, SUSY  | 110-2  | 210-3  | 110-2  |
| xq/l, LR 
 | 110-2   | 110-3  |  310-2  |
| Higgs  | 3/tan |  0.4/tan | 0.3/tan |

*Current status of ALL EDM searches*

- Best limits on “natural” parameters from 3 complementary experiments:

## General method to detect an EDM

- Energy level picture:

- Figure of merit for
- statistical sensitivity:

## E-field on an electron? (part I)

*E-field on an electron? (part I)*

- electric forces can be cancelled by _***magnetic***_ forces:** **

- <**F**tot> = <**F**el + **F**mag> = 0, <**E**eff> = -<**F**mag>/e

- magnetic forces
- arise from
- spin-orbit interaction:

## E-field on an electron? (part II)

- simple estimate: |<**E**eff>|  Z32 (e/a02)  P

- ~ P  1011 V/cm @ Z~80!

- polarization P required to unbalance
- vector average of **F***mag* (external **E** necessary!)

- <**E**int> = 0

- Sandars

## Tl EDM schematic

- State of the art
- electron EDM search:the Berkeley
- Tl beam experiment

-  Thermal beam of
-    atomic Tl (Z=81)
-  Efficient laser/rf spin
-   polarization & detection
-   count rate ~ 109/s
-  E =120 kV/cm (P ~10-3)
-     Eint = 70MV/cm
-  L=100 cm   T3 ms
-  Counterpropagating
-    vertical beams to cancel
-    systematic effects from
-    **B**motional = **E ** **v**/c
-    (*but:* complex procedure
-    to null residuals)

-  B-field noise rejection with side-by-side regions

-  Na atoms
- (low Z, small enhancement)
- as “co-magnetometer”
- to check systematics
- (*but:* little utility in practice)

**New electron EDM limit:**
- B. Regan, E. Commins, C. Schmidt, D. DeMille
- Phys. Rev. Lett. **88**, 071805 (2002)
**|d****e****| < 1.6********10****-27**** e********cm (90% c.l.)**

## Systematic effects: B correlated with E (part 1)

- Example 1:
- leakage current **I**  **E**  **B**E  **E**

- electron
- magnetic
- moment
- e  1016 de!
- Very small
- values
- BE ~ 10-11 G significant

-   |**B**tot|
- = |**B**0 + **B**E|
- changes
- on reversal of **E**

**B**0

**B**E

**E**

## Systematic effects: B correlated with E (part 2)

- y = v(x)E(z)

- E(z)

- misaligned B0

- Btotal (+E)

- Btotal (-E)

- Bmot (+E)

- Bmot (-E)

-  If **B**0** **and **E** are not exactly parallel,
-   |**B**tot| = |**B**0 + **B**mot| changes on reversal of **E**:

_**Solution:**_**  **avg. over counterpropagating beams   residuals are product of two imperfections (i.e., one v-mismatch  one wrong B-component)

- Example 2:  motional magnetic field **B**mot = **E****v**/c

## A new generation of electron EDM searches

| Group | System | Advantages | Projected gain |
| --- | --- | --- | --- |
| D. Weiss (Penn St.) | Trapped Cs | Long coherence | ~100 |
| D. Heinzen (Texas) | Trapped Cs | Long coherence | ~100 |
| H. Gould (LBL) | Cs fountain | Long coherence | ? |
| L. Hunter (Amherst) | GdIG | Huge S/N | 100? |
| S. Lamoreaux (LANL) | GGG | Huge S/N | 100?-100,000? |
| E. Hinds (Imperial) | YbF beam | Internal E-field | 2-? |
| D. DeMille (Yale) | PbO* cell | Internal E-field | 100-10,000? |
| E. Cornell (JILA) | trapped HBr+ | Int. E + long T | ?? |
| N. Shafer-Ray (Okla.) | trapped PbF | Int. E + long T | ?? |

## Electron EDM with cold trapped atoms

- Linear Photodiode
- Array

- 10 cm

*Electron EDM with cold trapped atoms*

- and guide beams

- Atoms loaded from below

- David Weiss *et al. *(& similar D. Heinzen *et al. *)

- Coherence time:

- Atom number:

- Cs (Z=55) EDM
- plus Rb(Z=37) comagnetometer

- x100 for Cs Eint

- de ~ 10-29 ecm
- for both Cs and Rb
- in ~1 day

## Solid state electron EDM searches

- Shapiro
- Lamoreaux
- DeMille

## A new direction in EDM searches:using molecules to search for de 

**** ***Extremely*** large effective E-field
- with lab-size external field:
**P ****~ 1 ******** E****eff**** ~ 10****11**** V/cm **
- (For atoms, P ~ 10-3 @ Eext ~ 100kV/cm)
**** Smaller signals due to
- thermal distribution over rotational levels (~10-4)
**** Molecules with unpaired electron spins are thermodynamically disfavored
-  high temperature chemistry, even smaller signals

## Addressing some problems with molecules:the metastable a(1)[3+] state of PbO

-    PbO is thermodynamically stable
- (routinely purchased and vaporized)
- a(1) populated via laser excitation** **(replaces chemistry)
** **
-  a(1) has very small -doublet splitting
****** **complete polarization with very small fields (>10 V/cm),
- equivalent to E 107 V/cm on an atom!
** **
****** ****can work in vapor cell**
- (***MUCH*** larger density and volume than beam)
**PbO Cell:****	****	****	****   Tl Beam:**
- N = nV ~ 1016		N = nV ~ 108

## Amplifying the electric field E with a polar molecule 

**E****int**

**Pb****+**

**O****–**

- Eext

**Complete molecular polarization **
**of PbO* **
**achieved at **
**E****ext**** ~ 10 V/cm**

**Explicit calculations indicate valence electron feels **
**E****int ****~ ********2****Z****3**** e/a****0****2**** ~ 1.8 - 4.0 ******** 10****10**** V/cm**
- semiempirical: M. Kozlov & D.DeMille, PRL **89**, 133001 (2002);
*ab initio*: T. Isaev *et al.*, PRA **69**, 030501 (2004); A. Titov, priv. comm.

## Populating the a(1) [3+] state of PbO 

-         Laser pulse
-          ~ 571 nm
-     bandwidth ~
-     1 GHz ~ Doppler

## An aside: what’s an -doublet?

- 

- Non-rotating molecule
- has internal
- tensor Stark shift

## Spin alignment & molecular polarization in PbO (no EDM)

## EDM measurement in PbO*:New mechanisms for suppressing systematics!

*  **Most systematics *
*      **cancel in *
*    **comparison!*

## The cruel reality of precision measurements (c.f. S. Freedman)

****

**Farmer   ****::****     Pig     ****::****   Truffle**** **

**Theorist ****:: ****Experimentalist ****:: ****Fact**

## PbO vapor cell and oven

**Sapphire **
**windows**
**bonded to ceramic frame with **
**gold foil “glue”**

**quartz oven body**
**800 C capability**
**wide optical access**
**w/non-inductive heater **
**for fast turn-off**

**Gold foil electrodes and “feedthroughs”**

## Present Experimental Setup 

- Pulsed Laser Beam
- 5-40 mJ @ 100 Hz
-  ~ 1 GHz
****  **B**

- Larmor
- Precession
-  ~ 100 kHz

- Photo-
- multiplier tube

**B**

- solid quartz
- light
- pipes

- Data
- Processing

- Vacuum
- chamber

**E**

## The PbO EDM lab

- .001 km

## Zeeman quantum beats in PbO

*Zeeman quantum beats in PbO*

- Excellent fit to Monte Carlo w/PbO motion, known lifetime
- Shot-noise limited S/N in frequency extraction

## RF electric resonance in PbO

-    Zeeman splitting ~ 450 kHz

- Zeeman splitting slightly different in lower level

- ~11 MHz RF E-field
- drives transitions

- ~1.6 ppt shift
- in Zeeman
- beat freq.

- g/g =
- 1.6(4) 10-3

*** ****-doublet will be near-ideal *
*co-magnetometer*
-  Also:
- = 11.214(5) MHz;
- observed low-field
- DC Stark shift

## Current status:  a proof of principle

- PbO vapor cell technology in place
- Collisional cross-sections as expected anticipated density OK
- Signal sizes large, consistent with expectation;
- straightforward improvements will reach target count rate: 1011/s.
- Shot-noise limited frequency measurement
- using quantum beats in fluorescence
- g-factors of -doublet states match precisely
- co-magnetometer will be very effective
- E-fields of required size applied in cell; no apparent problems

****** *****First EDM data in fall 2004;***
*******d******e***** ~ 10****-29**** *****e************cm within ~2 years***

- [D. Kawall *et al.,* PRL **92**, 133007 (2004)]

## The PbO EDM group

_*Postdocs:*_
**David Kawall**
**Val Prasad**
_*Grad students:*_
- Frederik Bay
**Sarah Bickman**
**Yong Jiang**
**Jonathan Jerke**
_*Undergrads:*_
- Cliff Cheung
**Yulia Gurevich**
_*Visitors:*_
**Rich Paolino (USCGA)**