  We consider the standard model with local scale invariance. The theory shows
exact scale invariance of dimensionally regulated action. We show that massless
gauge fields, which may be abelian or non-abelian, lead to vanishing
contribution to the cosmological constant in this theory. This result follows
in the quantum theory, to all orders in the gauge couplings. However we have
not considered contributions higher orders in the gravitational coupling.
Similarly we also find that massless fermion fields yield null contribution to
the cosmological constant. The effective cosmological constant in this theory
is non-zero due to the phenomenon of cosmological symmetry breaking, which also
gives masses to all the massive fields, besides generating the Planck mass. We
find a simple relationship between the curvature scalar and the vacuum value of
the Higgs field in the limit when we ignore all other contributions to the
energy density besides the vacuum energy.
