Lorentz and CPT symmetry tests with atoms and antimatter

4 problems

• Does antihydrogen 1S-2S match hydrogen at $10^{-15}$?

  Open

  Antihydrogen (an antiproton bound to a positron) should have exactly the same energy levels as hydrogen if matter and antimatter mirror each other perfectly. The main ultraviolet line has been compared to a few parts in $10^{12}$; hydrogen itself is known about a thousand times better.

• Antihydrogen ground-state hyperfine splitting at the ppm level

  Open

  The tiny splitting caused by the magnetic interaction of the antiproton and positron is sensitive to different possible symmetry violations than the optical line. It has been measured only to a few parts in 10000.

• Proton and antiproton magnetic moments compared at $10^{-12}$

  Open

  A single proton or antiproton held in an electromagnetic trap can have its magnetism measured by flipping its spin. Matter-antimatter symmetry requires the two magnetic moments to be equal and opposite.

• Are electron-sector Lorentz-violation coefficients nonzero at $10^{-23}$?

  Open

  If space had a preferred direction, an electron moving in an atom would have slightly different energy depending on how the atom is oriented as the Earth rotates. Clocks with oddly shaped electron orbitals are the most sensitive detectors of this.