  We propose a novel method in that quark-gluon tagging of the jets emitted as
initial state radiation (ISR) can boost searches of invisible Higgs from gluon
fusion processes against irreducible electroweak vector boson productions.
While quark ISR typically takes up a dominant portion than gluon in the
background processes mainly by frequent quark-gluon initiated hard scatterings
at the LHC, gluon ISR portion in the gluon fusion can be significantly larger
in the central region of detector. Focusing on invisible Higgs searches using
jet substructure variables capturing the new features, we demonstrate that
Higgs from gluon fusion constrains invisible Higgs decays the most, over vector
boson fusion traditionally known as the most constraining, and the limit on the
branching ratio is significantly improved. We summarize with emphasizing that
our method has wider implications in search for new resonances from gluon
fusion processes.
