A massless Weyl-invariant dynamics of a scalar, a Dirac spinor, and electro
mag netic fields is formulated in a Weyl space, W-4,W- allowing For conform
al rescalings of the metric and of all fields with nontrivial Weyl weight t
ogether with the associated transformations of the Weyl vector fields kappa
(mu), representing the D(1) gauge fields, with D(1) denoting the dilatation
group. To study the appearance of nonzero masses in the theory the Weyl sy
mmetry is broken explicitly and the corresponding reduction of the Weyl spa
ce W-4 to a pseudo-Riemannian space V-4 is investigated assuming the breaki
ng to be determined by an expression involving the curvature scalar R of th
e W-4 and the mass of the scalar, self-interacting field. Thereby also the
spinor field acquires a mass proportional to the modulus Phi of the scaler
field in a Higgs-type mechanism Formulated here in a Weyl-geometric setting
with Phi providing a potential for the Weyl vector fields ii,. After the W
eyl-symmetry breaking, one obtains generally covariant and U(1) gauge covar
iant field equations coupled to the metric of the underlying V-4. This metr
ic is determined by Einstein's equations, with a gravitational coupling con
stant depending on Phi, coupled to the energy momentum tensors of the now m
assive fields involved together with the (massless) radiation fields.