  Gauge bosons associated with unbroken gauge symmetries, under which all
standard model fields are singlets, may interact with ordinary matter via
higher-dimensional operators. A complete set of dimension-six operators
involving a massless U(1) field, gamma-prime, and standard model fields is
presented. The mu to e gamma-prime decay, primordial nucleosynthesis, star
cooling and other phenomena set lower limits on the scale of chirality-flip
operators in the 1 - 15 TeV range, if the operators have coefficients given by
the corresponding Yukawa couplings. Simple renormalizable models induce
gamma-prime interactions with leptons or quarks at two loops, and may provide a
cold dark matter candidate.
