Probing radiative neutrino mass models with dilepton events at the LHC

In this work, we investigate the possibility of probing a class of neutrino mass models at the LHC proton-proton collisions with 8 and 14 TeV energies. The existence of lepton flavor violating interactions for a singlet charged scalar, $S^{\pm }$, that couples to the leptons could induce many processes such as $pp\to {\ell }_{\alpha }^{\pm }{\ell }_{\beta }^{\mp }+\cancel{E}$. Using the processes with ${\ell }_{\alpha }{\ell }_{\beta }=ee$, $e\mu$, $\mu \mu$, we found that an inclusive cut on the $M_{T2}$ event variable is vital in our analysis and leads to an effective suppression of the large Standard Model background. Our results show possible detectability of the charged scalars effect, especially at the $\sqrt{s}=14\mathrm{TeV}$.

Figure 1

The Feynman diagrams of the charged scalar $S^{\pm }$ pair production via the gluon-gluon fusion and quark-antiquark annihilation at proton-proton collisions.

Figure 2

Left: the production cross section (in fb units) of $S^{+}{S}^{-}$ pair production at $\sqrt{s}=8\mathrm{TeV}$ (in magenta) and 14 TeV (in blue) vs the charged scalar mass $M_S$. The dashed black lines represent the DY values. Right: the ratio $[{\sigma }^{\text{full}}(s)-{\sigma }^{(\mathrm{DY})}(s)]/{\sigma }^{(\mathrm{DY})}(s)$ vs the charged scalar mass ($M_S$). The considered $M_S$ values are in agreement with different experimental constraints such as LFV and the Higgs decay $h\to \gamma \gamma$.

Figure 3

The charged scalar total decay width (left) and its different branching ratios (right) vs $M_S$. The considered values of the charged scalar mass and the Yukawa couplings $f_{\alpha \beta }$ are in agreement with the experimental constraints mentioned above.

Figure 4

The cross section (in fb units) of different contributions (solid lines) of the missing energy for each process as a function of the center of mass (in TeV). Here, the dashed lines represent the SM values.

Figure 5

The significance vs the luminosity at $\sqrt{s}=8\mathrm{TeV}$ (left) and at $\sqrt{s}=14\mathrm{TeV}$ (right) for the three different signatures. The two horizontal dashed lines in each panel indicate the corresponding significance values for $S=3$ and $S=5$, respectively.

Figure 6

The significance vs the mass of the charged scalar $M_S$ for each channel at $\mathrm{L}=20{\mathrm{fb}}^{-1}$ (left) and at $\mathrm{L}=100{\mathrm{fb}}^{-1}$ (right). The two dashed horizontal lines indicate the significance values at $\mathrm{S}=3$ and $\mathrm{S}=5$, and the vertical one indicates the charged scalar mass given (9).