Probing the NMSSM via Higgs boson signatures from stop cascade decays at the LHC

Higgs signatures from the cascade decays of light top squarks are an interesting possibility in the next-to-minimal supersymmetric standard model (NMSSM). We investigate the potential reach of the light top-squark mass at the 13 TeV run of the LHC by means of five NMSSM benchmark points where this signature is dominant. These benchmark points are compatible with current Higgs coupling measurements, LHC constraints, dark matter relic density and direct-detection constraints. We consider single and dilepton search strategies, as well as the jet-substructure technique to reconstruct the Higgs bosons. We find that one can probe top-squark masses up to 1.2 TeV with $300{\mathrm{fb}}^{-1}$ luminosity via the dilepton channel, while with the jet-substructure method, top-squark masses up to 1 TeV can be probed with $300{\mathrm{fb}}^{-1}$ luminosity. We also investigate the possibility of the appearance of multiple Higgs peaks over the background in the fat-jet mass distribution, and conclude that such a possibility is viable only at the high-luminosity run of the 13 TeV LHC.

Figure 1

A sample Feynman diagram for the channel under consideration.

Figure 2

$p_T$ distribution of the leading two fat jets for the 13 TeV LHC. We reconstruct the jets using the C/A algorithm with jet radius $R=1.2$. The benchmark points BP1 and BP5 are as tabulated in Table 2.

Figure 3

The left panel shows the distribution of $H_T$ where $H_T={\mathrm{\Sigma }}_j{p}_T^j$ with the anti-$k_T$ jets selected after imposing the basic Higgs tagging criteria, while the right panel displays the distribution of the ${\cancel{p}}_T$ at the 13 TeV LHC.

Figure 4

The $M_{T2}$ distribution at the 13 TeV LHC for the benchmark points P1, P5 and the SM backgrounds $t\overline{t}{H}_{\mathrm{SM}}$ and $t\overline{t}+\text{jets}$.

Figure 5

Fat-jet mass distribution with 300 (left), 1000 (middle), and 3000 (right) ${\mathrm{fb}}^{-1}$ of luminosity, after all cuts as described by the jet-substructure analysis in the text. Here we plot the first six $p_T$-ordered fat-jet masses at the end of our selection cut (C5), and no extra $b$-tagging criteria on these fat jets are imposed expect the SM Higgs-like fat jets where we demand two $b$-tagged jets inside the fat jet. The reason behind this plot is to investigate the possibility of having multiple Higgs peaks in the fat-jet mass distributions. The figures are all normalized to the cross section with a particular choice of luminosity.