Derek F' Jackson Kimball

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A new search for aspin-gravity interaction

• Derek F. Jackson Kimball

Eric Bahr, Valentin Dutertre, Srikanth
Guttikonda, Rene Jacome, and Khoa Nguyen
Funded by the National Science Foundation
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Dima Budker and friends.
Only 30 min from UC Berkeley!
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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 dont fit together
  nicely.

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A spin-gravity coupling?
Many physicists have proposed the possibility of
a long-range spin-gravity coupling...
Hamiltonian in Earths field
Shift of Zeeman sublevels
Spin precession
?
g
?
S
?0
?E
M -1 M 0 M 1
F1 ? F0
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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.

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Violates Equivalence Principle!
?
?
g
a
No spin precession in accelerating frame.
Gravitational field causes spin precession.
Violates parity conservation and time-reversal
invariance!
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Distinct from some other sources of spin-mass
couplings
Lense-Thirring precession
General relativistic frame-dragging (Gravity
Probe B)
Axions
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Previous Searches
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Previous Searches
Best limit on gravitational dipole
moment Venema, Majumder, Lamoreaux, Heckel,
Fortson (1992). PRL 68, 135.
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Need sensitive measurement of atomic
spin-precession...
See Rene Jacomes talk to follow...
Nonlinear Magneto-Optical Rotation with
Frequency-modulated Light (FM NMOR)
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Projected sensitivity of FM NMOR to Zeeman shifts
Sensitivity to precession frequency is
sufficient to search for k1.
Improvement of 100 times!
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FM NMOR Gyroscope
87
Rb
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Electron spin serves as co-magnetometer for
nuclear spin
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Experimental Setup
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Systematic Effects

• Magnetic fields and gradients
• Earths rotation
• Collisional effects
• Nonlinear Zeeman effect
• AC Stark shifts due to optical fields
• Apparatus misalignments
• Geometric (Berrys) Phase

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Systematic Effects
Nuclear magnetic moment can generate ??
0.3 Hz for B 1 mG!
Controlled by magnetic field reversal and precise
measurement of B via FM NMOR.
?? ? 10-9 Hz
nucl
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Systematic Effects
Earths rotation can generate ??
Atomic spins are effectively decoupled from
laboratory spins inertial frame viewed from
noninertial lab frame.
?
? 11.6 ?Hz
E
?
1
B
1
?
E
?
1
g
Solution? Align B along ? to make effect
quadratic in misalignment, transverse field
resonances enable precise alignment.
1
1
E
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Where are we now?
5-layer magnetic shield constructed magnetic
field reduced 10,000,000 times!
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Where are we now?
Set of 7 independent coils designed and mount
built for precise control of magnetic fields.
Special antirelaxation- coated cells manufactured
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Where are we now?
Laser system and optics being tested...
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Where are we now?
Having lots of fun!
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Future

• Working on FM NMOR setup, optimizing
• magnetometric sensitivity...
• Demonstrate FM NMOR gyro and optimize
• sensitivity (amplitudes of F2,1 resonances).
• Detect nuclear magnetic moments, Earths
• rotation ? sensitivity test.
• Study collisional effects, Berrys phase.
• Look for spin-gravity coupling!