  In massive scalar-tensor gravity, core-collapse supernovae are strong sources
of scalar-polarized gravitational waves. These can be detectable out to large
distance. The dispersive nature of the propagation of waves in the massive
scalar field mean the gravitational wave signals are long lived and many such
signals can overlap to form a stochastic background. Using different models for
the population of supernova events in the nearby universe, we compute
predictions for the energy-density in the stochastic scalar-polarized
gravitational wave background from core-collapse events in massive
scalar-tensor gravity for theory parameters that facilitate strong
scalarization. The resulting energy density is below the current constraints on
a Gaussian stochastic gravitational wave background but large enough to be
detectable with the current generation of detectors when they reach design
sensitivity, indicating that it will soon be possible to place new constraints
on the parameter space of massive scalar-tensor gravity.
