  We study interference effects in the production channel ZZ + jet, in
particular focusing on the role of the Higgs boson. This production channel
receives contributions both from Higgs boson-mediated diagrams via the decay $H
\to ZZ$ (signal diagrams), as well as from diagrams where the Z-bosons couple
directly to a quark loop (background diagrams). We consider the partonic
processes $gggZZ$ and $gq \bar{q} ZZ$ in which interference between signal and
background diagrams first occurs. Since interference is primarily an
off-resonant effect for the Higgs boson, we treat the Z-bosons as on-shell.
Thus our analysis is limited to the region above threshold, where the invariant
mass of the Z-pair, $m_{ZZ}$, satisfies the condition $m_{ZZ}>2m_Z$. In the
region $m_{ZZ} > 300$ GeV we find that the interference in the ZZ + jet channel
is qualitatively similar to interference in the inclusive ZZ channel. Moreover,
the rates are sufficient to study these effects at the LHC once jet-binned data
become available.
