Investigation of the gravitational-potential dependence of the fine-structure constant using atomic dysprosium

Radio-frequency E1 transitions between nearly degenerate, opposite-parity levels of atomic dysprosium (Dy) were monitored over an 8-month period to search for a variation in the fine-structure constant {alpha}. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of (-8.7{+-}6.6)x10{sup -6} for k{sub {alpha}}, the variation of {alpha} in a changing gravitational potential. This value gives the first laboratory limit independent of assumptions regarding other fundamental constants. In addition, our value of k{sub {alpha}} combined with other experimental constraints is used to extract the first limits on k{sub e} and k{sub q}. These coefficients characterize the variation of m{sub e}/m{sub p} and m{sub q}/m{sub p} in a changing gravitational potential, where m{sub e}, m{sub p}, and m{sub q} are electron, proton, and quark masses. The results are k{sub e}=(4.9{+-}3.9)x10{sup -5} and k{sub q}=(6.6{+-}5.2)x10{sup -5}. All these results indicate the absence of significant variation at the present level of sensitivity.