New limits on coupling of fundamental constants to gravity using Sr87 optical lattice clocks

Abstract

The S01-P03 clock transition frequency I Sr in neutral Sr87 has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the 1 10-15 level makes I Sr the best agreed-upon optical atomic frequency. We combine periodic variations in the Sr87 clock frequency with Hg+199 and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant α, electron-proton mass ratio I, and light quark mass. Furthermore, after Hg+199, Yb+171, and H, we add Sr87 as the fourth optical atomic clock species to enhance constraints on yearly drifts of α and I. © 2008 The American Physical Society.