Charged Higgs bosons in the NMSSM under current LHC constraints

Charged Higgs boson is a crucial prediction of new physics beyond the SM. In this work, we perform a comprehensive scan over the parameter space of NMSSM considering various experimental constraints including the direct search limits from the 13 TeV LHC, and consider the scenario that the next-to-lightest CP-even Higgs boson is SM-like. We find that the masses of charged Higgs bosons can be as light as 350 GeV, the lightest CP-even Higgs boson $h_1$ is predominantly singlet and can be as light as 48 GeV, and the lightest CP-odd Higgs boson $a_1$ is also singlet-dominated and can be as light as 82 GeV. The charged Higgs bosons mainly decay to $t\bar{b}$ or $\bar{t} b$, but the branching ratio of the exotic decays $H^\pm\to W^\pm h_1$ and $H^\pm\to W^\pm a_1$ can maximally reach to 20\% and 11\%, respectively, which can be used to distinguish the NMSSM from MSSM. Such a heavy charged Higgs boson is unaccessible at the 13 TeV LHC with a luminosity of 36.1 $\rm fb^{-1}$ and its detection needs higher energy and/or higher luminosity.