paper

MICROSCOPE limits for new long-range forces and implications for unified theories

arXiv:1712.00856 · doi:10.1103/PhysRevD.97.055039

Abstract

Many theories beyond the Standard Model involve an extra U(1) gauge group. The resulting gauge boson U, in general mixed with the Z and the photon, may be massless or very light, and very weakly coupled. It may be viewed as a generalized dark photon interacting with matter through a linear combination (ε_Q Q + ε_B B+ε_L L) e, involving B-L in a grand-unified theory, presumably through B-L-.61 Q, inducing effectively a very small repulsive force between neutrons. This new force, if long-ranged, may manifest through apparent violations of the Equivalence Principle. They are approximately proportional to ε_B+ε_L/2, times a combination involving mostly ε_L. New forces coupled to B-L or L should lead to nearly opposite values of the Eötvös parameter δ, and to almost the same limits for ε_{B-L} or ε_L, as long as no indication for δ\neq 0 is found. We derive new limits from the first results of the MICROSCOPE experiment testing the Equivalence Principle in space. A long-range force coupled to (ε_Q Q + ε_{B-L} (B-L)) e or (ε_Q Q + ε_L L) e should verify |ε_{B-L}| or |ε_L| < .8 10^{-24}, and a force coupled to (ε_Q Q + ε_B B) e, |ε_B| < 5 10^{-24}. We also discuss, within supersymmetric theories, how such extremely small gauge couplings g", typically \simle 10^{-24}, may be related to a correspondingly large ξ"D" term associated with a huge initial vacuum energy density, \propto 1/g"^2. The corresponding hierarchy between energy scales, by a factor \propto 1/\sqrt g" \simge 10^{12}, involves a very large scale ~ 10^{16} GeV, that may be associated with inflation, or supersymmetry breaking with a very heavy gravitino, leading to possible values of δ within the experimentally accessible range.

13 pages. Phys. Rev. D, in press. Journal version, with systematic and statistical errors combined in quadrature

References in corpus (5)

Cited by in corpus (46)