[$\PH\to\ccbar$]{}decay mode, the analysis is split into two separate searches involving different topologies: the “resolved-jet” topology, in which the boson candidate is reconstructed from two well-separated and individually resolved charm quark jets, and the “merged-jet” topology, in which the hadronization products of the two charm quarks are reconstructed as a single jet. The former focuses on boson candidates with lower transverse momentum, , while the latter performs better for boson candidates with high . In practice, the two topologies can have significant overlap and so, for the final result, the two are made distinct by defining them in reference to whether the boson in the event has [$\pt(\PV)$]{}below or above a single threshold chosen to maximise the sensitivity to the [$\PV\PH(\PH\to \PQc \PAQc)$]{}process.

The central feature of this search is the identification of charm quark jets. In both topologies, novel tools based upon advanced machine learning (ML) techniques are used for charm quark jet identification [@Sirunyan:2017ezt; @CMS-PAS-JME-18-002]. In addition, the merged-jet topology makes use of jet substructure information to further suppress the backgrounds.

The CMS detector
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The central feature of the CMS apparatus is a superconducting solenoid of 6 internal diameter, providing a magnetic field of 3.8. Within the 