  A search is presented for single production of heavy vector-like quarks (B)
that decay to a Higgs boson and a b quark, with the Higgs boson decaying to a
highly boosted $\mathrm{b\overline{b}}$ pair reconstructed as a single
collimated jet. The analysis is based on data collected by the CMS experiment
in proton-proton collisions at $\sqrt{s} =$ 13 TeV, corresponding to an
integrated luminosity of 35.9 fb$^{-1}$. The data are consistent with
background expectations, and upper limits at 95% confidence level on the
product of the B quark cross section and the branching fraction are obtained in
the range 1.28-0.07 pb, for a narrow B quark with a mass between 700 and 1800
GeV. The production of B quarks with widths of 10, 20 and 30% of the resonance
mass is also considered, and the sensitivities obtained are similar to those
achieved in the narrow width case. This is the first search at the CERN LHC for
the single production of a B quark through its fully hadronic decay channel,
and the first study considering finite resonance widths of the B quark.
