  Recently Weinberg suggested that Goldstone bosons arising from the
spontaneous breakdown of some global hidden symmetries can interact weakly in
the early Universe and account for a fraction of the effective number of
neutrino species N_eff, which has been reported persistently 1 \sigma away from
its expected value of three. In this work, we study in some details a number of
experimental constraints on this interesting idea based on the simplest
possibility of a global U(1), as studied by Weinberg. We work out the decay
branching ratios of the associated light scalar field $\sigma$ and suggest a
possible collider signature at the Large Hadron Collider (LHC). In some corners
of the parameter space, the scalar field \sigma can decay into a pair of pions
with a branching ratio of order O(1)% while the rest is mostly a pair of
Goldstone bosons. The collider signature would be gluon fusion into the
standard model Higgs boson gg -> H or associated production with a W gauge
boson q q'-bar -> H W, followed by H -> \sigma \sigma -> (\pi\pi)
(\alpha\alpha), where \alpha is the Goldstone boson.
