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Atomic Nuclei: Nuclear Spin01:08

Atomic Nuclei: Nuclear Spin

All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although protons and neutrons in nuclei may have higher half-integer spins owing to energetic factors.
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Setting Limits on Supersymmetry Using Simplified Models
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Published on: November 15, 2013

Limits on anomalous spin-spin couplings between neutrons.

Alexander G Glenday1, Claire E Cramer, David F Phillips

  • 1Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.

Physical Review Letters
|December 31, 2008
PubMed
Summary

Researchers set new limits on undiscovered forces between neutrons, searching for axion-like particles. This study explores spin-dependent interactions using a helium-3/xenon-129 maser, constraining new physics beyond the Standard Model.

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Area of Science:

  • Experimental Physics
  • Particle Physics
  • Nuclear Physics

Background:

  • The Standard Model of particle physics does not account for all observed phenomena, motivating searches for new particles and forces.
  • Axions and other light pseudoscalar particles are hypothetical candidates for dark matter and can mediate novel spin-dependent interactions.
  • Previous experiments have searched for such interactions, but limits can be improved with more sensitive techniques.

Purpose of the Study:

  • To experimentally constrain the coupling strength of new spin-dependent macroscopic forces between neutrons.
  • To search for evidence of axion-like particles mediating neutron spin-spin interactions.
  • To establish new limits on hypothetical interactions beyond the Standard Model.

Main Methods:

  • Utilized a helium-3/xenon-129 (3He/129Xe) maser to measure nuclear Zeeman frequencies.
  • Modulated the nuclear spin polarization of a nearby 3He ensemble in a separate glass cell.
  • Analyzed frequency shifts in the maser to infer limits on neutron spin-spin interactions.

Main Results:

  • Established experimental limits on the coupling strength of neutron spin-spin interactions mediated by light pseudoscalar particles.
  • Achieved a coupling strength limit of [g(p)g(p)/(4pihc)] at the 3 x 10(-7) level for interaction ranges greater than 40 cm.
  • The obtained limit is approximately 10(-5) times the strength of the magnetic dipole-dipole interaction between neutrons.

Conclusions:

  • The experiment provides stringent new limits on new spin-dependent macroscopic forces involving neutrons.
  • The findings constrain the parameter space for axion-like particles and other new physics scenarios.
  • This work demonstrates a sensitive method for probing hypothetical interactions at macroscopic distances.