Exploring the doubly charged Higgs boson of the left-right symmetric model using vector boson fusionlike events at the LHC

This paper studies the pair production of the doubly charged Higgs boson of the left-right symmetric model using a multilepton final state in the vector boson fusionlike processes. The study is performed in a framework consistent with the model’s correction to the standard model ${\rho }_{\mathrm{EW}}$ parameter. Vector boson fusion topological cuts, the number of leptons, and $p_T$ cuts on the leptons are found to be effective in suppressing the background. Significant mass reach can be achieved for exclusion/discovery of the doubly charged Higgs boson for the upcoming LHC run with a luminosity of $\mathcal{O}(10^3){\mathrm{fb}}^{-1}$.

Figure 1

Same-value $\mathrm{\Delta }m$ contours (dashed) as a function of $m_{{\delta }_L^0}$ and $\delta \alpha$, where $\mathrm{\Delta }m=m_{{\delta }_L^{++}}-m_{{\delta }_L^{+}}$. The constraint $\mathrm{\Delta }{\rho }_{\mathrm{EW}}=0.001$ is shown by the black thick line. The shaded region is excluded.

Figure 2

Left: Cross section for $pp\to {\delta }_L^{++}{\delta }_L^{--}jj+{\delta }_L^{\pm \pm }{\delta }_L^{\mp }jj$ at LHC14 for different values of $\mathrm{\Delta }m$, where $\mathrm{\Delta }m=m_{{\delta }_L^{++}}-m_{{\delta }_L^{+}}$. Right: Comparison of the production cross sections for $pp\to {\delta }_L^{++}{\delta }_L^{--}jj$ and $pp\to {\delta }_L^{++}{\delta }_L^{--}jj+{\delta }_L^{\pm \pm }{\delta }_L^{\mp }jj$ at LHC14, keeping $\mathrm{\Delta }m\approx 40\mathrm{GeV}$ fixed for all $m_{{\delta }_L^{\pm \pm }}$.

Figure 3

Distribution of the dijet invariant mass $M_{j_1{j}_2}$ normalized to unity for the tagging jet pair $(j_1,j_2)$ for the signal and all the backgrounds before the VBF cuts are applied. The signal is inclusive of the processes ${\delta }_L^{++}{\delta }_L^{--}jj$ and ${\delta }_L^{\pm \pm }{\delta }_L^{\mp }jj$ for the benchmark point $(m_{{\delta }_L^{++}},m_{{\delta }_L^{+}})=(460\mathrm{GeV},420\mathrm{GeV})$ at $\sqrt{s}=14\mathrm{TeV}$. The tagged jets $(j_1,j_2)$ are the pair of jets with largest dijet invariant mass among all final-state jet pairs. $j_1$ and $j_2$ have been sorted among themselves by their $p_T$.

Figure 4

$p_T$ distribution of the leptons, normalized to unity, in the $\ge 3l+\ge 2j$ final state for the signal $[(m_{{\delta }_L^{++}},m_{{\delta }_L^{+}})=(460\mathrm{GeV},420\mathrm{GeV})]$ and SM backgrounds at $\sqrt{s}=14\mathrm{TeV}$.

Figure 5

Left: The signal invariant mass distribution of like-sign dilepton pairs in the $\ge 3l+\ge 2j$ final state, after applying all the kinematic cuts. Since the number of background events drops to less than 1 after all the cuts, they have not been included in this figure. Right: The significance curves assume $1000{\mathrm{fb}}^{-1}$ (solid) and $3000{\mathrm{fb}}^{-1}$ (dot-dashed) LHC luminosities at 14 TeV. The $3\sigma$ and $5\sigma$ levels are shown as horizontal lines, and $\mathrm{\Delta }m$ is kept at $\approx 40\mathrm{GeV}$.

Figure 6

$p_T$ distribution of the ${\tau }_h\mathrm{s}$, normalized to unity, in the $\ge 3{\tau }_h+\ge 2j+{\cancel{E}}_{\mathrm{T}}$ final state for the signal $[(m_{{\delta }_L^{++}},m_{{\delta }_L^{+}})=(210\mathrm{GeV},170\mathrm{GeV})]$, as well as SM backgrounds at $\sqrt{s}=14\mathrm{TeV}$. For all the plots, the $\tau$ ID efficiency and $\text{jet}\to {\tau }_h$ fake rate are considered to be 70% and 2%, respectively.

Figure 7

The visible mass of the like-sign ${\tau }_h$ pair for the signal (dotted) and backgrounds (solid and dashed) for the $\ge 3{\tau }_h+\ge 2j+{\cancel{E}}_{\mathrm{T}}$ final state, after all the kinematic cuts. $(m_{{\delta }_L^{++}},m_{{\delta }_L^{+}})=(210\mathrm{GeV},170\mathrm{GeV})$, with $\epsilon =70\%$ and $f=2\%$ at 14 TeV.

Figure 8

The ${\tau }_h$ channel significance versus $m_{{\delta }_L^{++}}$ for ${\tau }_h$ ID efficiency $\epsilon =50\%$ with the jet fake rate $f=1\%$ (left panel) and for $\epsilon =70\%$, $f=2\%$ (right panel). The LHC energy is 14 TeV, and $\mathrm{\Delta }m$ is kept at 40 GeV. The significances for luminosities at 1000 and $3000{\mathrm{fb}}^{-1}$ are plotted as solid and dot-dashed curves, respectively.