Radio-frequency E1 transitions between nearly degenerate, opposite parity
levels of atomic dysprosium were monitored over an eight month period to search
for a variation in the fine-structure constant. 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)×10−6 for the fit parameter kα. This
value gives the current best laboratory limit. In addition, our value of
kα combined with other experimental constraints is used to extract
the first limits on k_e and k_q. These coefficients characterize the variation
of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p,
and m_q are electron, proton, and quark masses. The results are ke=(4.9±3.9)×10−5 and kq=(6.6±5.2)×10−5.Comment: 6 pages, 3 figure