  In the top quark pair production in association with the Higgs boson decaying
to a b quark pair t-tbar H (b-bbar), the final state has an irreducible
nonresonant background from the production of a top quark pair in association
with a b quark pair t-tbar b-bbar. Therefore, understanding of the t-tbar
b-bbar process precisely in particular differential cross-section as functions
of the properties of the additional b jets not from the top quark decay is
essential for improving the sensitivity of a search for the t-tbar H b-bbar
process. The two additional b jets can be identified by using various
approaches. In this paper, the performances are compared quantitatively in the
lepton+jets decay channel in terms of the matching efficiency of assigning two
additional b jets as a figure of merit. This study provides valuable
information towards the precise measurement of differential cross-sections as a
function of properties of the additional b jets in the t-tbar b-bbar events. We
showed that a matching efficiency of around 40% could be achieved using a deep
neural network method. In the events with at least 4 b jets, this performance
is 8% better than that achieved using minimum Delta R(b,bbar) method. This is
consistent with the boosted decision tree method within its statistical
uncertainty.
