Test of special relativity

Motivation

All accepted theories dealing with the description of the fundamental interactions in nature are based on the invariant Lorentz-transformation. The Standard Model as well as general and special relativity depend strongly on the validity of this tranformation. This is a strong motivation to test the theory of special relativity (SR) experimentally with ever higher precision, as any deviation from its predictions would have profound consequences for our understanding of nature.

Technical aspects

Heavy ion storage rings equipped with electron coolers like the Test Storage Ring (TSR) at the Max-Planck-Institute for Nuclear Physics in Heidelberg and the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, respectively, provide low-divergence ion beams at high velocities. The combination of these fast ion beam techniques with high resolution laser spectroscopy allows for a modern version of the classical Ives-Stilwell experiment, which measures relativistic time dilation via the transverse Doppler-effect.

Experiments and Results

Test Storage Ring (TSR) at the Max-Planck-Institute for Nuclear Physics in Heidelberg

In the latest experiments at the TSR metastable 7Li+ ions where accelerated and stored at a velocity of 3% c and 6.4% c, respectively. Those ions have an optical transition at rest that can be used for high precision spectroscopy. That transition is excited by two laser beams travelling parallel and antiparallel with respect to the ions. The Doppler-shifted excitation wavelengths of both lasers are measured simultaneously using saturation spectroscopy technique for each of the two ion velocities. Comparing measured and predicted frequencies leads to a new upper limit of 8.4 x 10-8 for deviations from SR.
Ref.: S. Reinhardt et.al Nature Physics 3 (2007) 861-864 (to press release)

Setup with the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt - click for big version

The next step is to perform this type of experiment at the ESR with an ion-velocity of 34% c. Due to the higher velocity an increase in sensitivity of more than a factor ten is possible. First experiments had already shown the feasibility for this test.
Ref.: C. Novotny et.al Hyperfine Interactions 171 (2006) 57-67

Wavelength plotted against ion velocity - click for bigger version