# Presentation: 632409

## Derek F. Jackson Kimball

**A new search for a**_**spin-gravity interaction**_

- Funded by the National Science Foundation

- Eric Bahr, Valentin Dutertre, Srikanth Guttikonda,
- Rene Jacome, and Khoa Nguyen

## Only 30 min from  UC Berkeley!

- Dima Budker
- and friends.

## Guess

- Within next 10-50 (?) years, our present
- understanding of gravity will be radically revised.

-   Gravity is very weak, experiments are hard.
-   Most tests of General Relativity are observational.
-   Lots of mysteries are somehow associated with 	gravity:
- 	- Dark Matter
- 	- Dark Energy
-   GR and quantum mechanics don’t fit together nicely.

## A spin-gravity coupling?

**A spin-gravity coupling?**

- Many physicists have proposed the possibility
-  of a long-range spin-gravity coupling...

- Hamiltonian in Earth’s field:

- *E*

- 0

* **M *= -1                *M *= 0              *M *= 1

***F=1 ************ F’=0****** ***

- _Shift of Zeeman sublevels_

- _Spin precession_

- g

- 

- 

- S

## A spin-gravity coupling?

- What might cause a spin-gravity interaction?

- _Truth_:  Who knows?

- _Guesses_:

-  _Einstein-Cartan Theory_: incorporates spin into
-    General Relativity, so that spin becomes generator of
-    a form of space-time curvature called torsion,
-    leads to various spin-mass couplings.

-  _Quantum theories of gravity_: often propose spin-1 and
-    spin-0 partners of the standard spin-2 graviton.
-    Spin-1, spin-0 gravitons can generate spin-mass couplings.

## Violates Equivalence Principle!

**Violates Equivalence Principle!**

- g

- 

- a

- 

- Gravitational field causes
- spin precession.

- No spin precession in
- accelerating frame.

- Violates parity conservation and
- time-reversal invariance!

## Distinct from some other 

**sources of spin-mass couplings:**

- Lense-Thirring
- precession

- General relativistic
- “frame-dragging”
- (Gravity Probe B)

- Axions

## Previous Searches

**Previous Searches**

## Previous Searches

_*Best limit on gravitational dipole moment:*_
- Venema, Majumder, Lamoreaux, Heckel, Fortson (1992). *PRL* 68, 135.

**Previous Searches**

## Need sensitive measurement

**Need sensitive measurement**
**of atomic spin-precession...**

- Nonlinear Magneto-Optical Rotation
- with Frequency-modulated Light
- (FM NMOR)

- See Rene Jacome’s
- talk to follow...

## Projected sensitivity of FM NMOR to Zeeman shifts:

- Sensitivity to precession frequency is sufficient
- to search for k~1.

- Improvement of ~100 times!

## FM NMOR “Gyroscope”

- Rb

- 87

## Electron spin serves as co-magnetometer for nuclear spin:

## Experimental Setup

**Experimental Setup**

## Systematic Effects

- Magnetic fields and gradients
- Earth’s rotation
- Collisional effects
- Nonlinear Zeeman effect
- AC Stark shifts due to optical fields
- Apparatus misalignments
- Geometric (Berry’s) Phase

**Systematic Effects**

## Systematic Effects

- Nuclear magnetic moment can generate :

- Controlled by magnetic field reversal and
- precise measurement of B via FM NMOR.

- 0.3 Hz
- for B = 1 mG!

-     10-9 Hz

- nucl

## Systematic Effects

**Systematic Effects**

- Earth’s rotation can generate :

- Atomic spins are effectively decoupled from laboratory:
- spins’ inertial frame viewed from noninertial lab frame.

- 

- E

-  11.6 Hz

_**Solution?**_
- Align B along    to make effect quadratic in misalignment,
- transverse field resonances enable precise alignment.

- E

****

****

- B

****

- g

****

- 

****

- E

- 

- 

## Where are we now?

**Where are we now?**

- 5-layer magnetic shield
- constructed:
- magnetic field reduced
- 10,000,000 times!

## Where are we now?

- Set of 7 independent coils
- designed and mount built
- for precise control of
- magnetic fields.

- Special antirelaxation-
- coated cells manufactured

## Where are we now?

- Laser system and optics being tested...

## Where are we now?

- Having lots of fun!

## Future

-  Working on FM NMOR setup, optimizing
-    magnetometric sensitivity...
-  Demonstrate FM NMOR “gyro” and optimize
- sensitivity (amplitudes of F=2,1 resonances).
-  Detect nuclear magnetic moments, Earth’s
- rotation  sensitivity test.
-  Study collisional effects, Berry’s phase.
-  Look for spin-gravity coupling!