Scalar-tensor theory offers the possibility of a modification of Newtonian gravity due to the presence of a 4d scalar dilaton field. The prototypical version of such a theory, massless Brans-Dicke theory, is considered here in the Einstein frame representation. The acceleration of a test mass is obtained from the exact 4d Xanthopoulos-Zannias solutions with spherical symmetry. The deviation of this acceleration from the pure Newtonian gravitational acceleration is examined to see if it can account for the anomalous Pioneer acceleration, while satisfying solar system constraints. Theoretical considerations, along with limits inferred from Pioneer 10 data, suggest that Brans-Dicke gravity could account for no more than a small fraction of the Pioneer anomaly, so that a complete explanation of the anomaly must lie elsewhere.

• Received 23 July 2012

DOI:https://doi.org/10.1103/PhysRevD.86.064023