  By evaluating the so-called Bose-ghost propagator, we present the first
numerical evidence of BRST-symmetry breaking for Yang-Mills theory in minimal
Landau gauge, i.e. due to the restriction of the functional integration to the
first Gribov region in the Gribov-Zwanziger approach. Our data are well
described by a simple fitting function, which can be related to a massive gluon
propagator in combination with an infrared-free (Faddeev-Popov) ghost
propagator. As a consequence, the Bose-ghost propagator, which has been
proposed as a carrier of the confining force in minimal Landau gauge, displays
a 1/p^4 singularity in the infrared limit.
