Color-octet scalar decays to a gluon and an electroweak gauge boson in the Manohar-Wise model

We present one loop results for the amplitudes giving rise to couplings between a color octet scalar, a gluon, and an electroweak gauge boson. These amplitudes could signal new physics in $\gamma$ jet, $Z$ jet and $W$ jet production at the LHC. We compute the relevant branching ratios and identify regions of parameter space where these decay modes become important. This can happen for scalar masses below the threshold for decay into heavy quark pairs ($t\overline{t}$ and $t\overline{b}$) or for small Yukawa couplings in which case the colored scalars are fermiophobic. In the case of light scalars, $\mathcal{B}(S\to \gamma g)$ can reach up to 10% whereas $\mathcal{B}(S\to Zg)$ can reach a few percent. In the fermiophobic region of parameter space, $\mathcal{B}(S\to \gamma g)$ and $\mathcal{B}(S\to Zg)$ can reach up to 72% and 28% respectively, whereas $\mathcal{B}(S\to gg)$ can be 100%. For the charged scalar, the decay mode $\mathcal{B}(S^{\pm }\to W^{\pm }g)$ can become dominant in both scenarios.

Figure 1

One-loop diagrams contributing to the factors appearing in Eq. (4) for the $S_{R,I}gg$ coupling.

Figure 2

One-loop diagrams contributing to the factors appearing in Eq. (4) for the $S_{R,I}\gamma g$ coupling.

Figure 3

One-loop diagrams contributing to the factors appearing in Eq. (4) for the $S_{R,I}Zg$ coupling.

Figure 4

One-loop diagrams contributing to the factors appearing in Eq. (4) for the $S^{\pm }{W}^{\mp }g$ coupling.

Figure 5

Branching ratios for $S_R$ decay in the fermiophilic scenario ${\eta }_U=5$, ${\eta }_D=1$ (left panel: ${\lambda }_{4,5}=0$, right panel: ${\lambda }_4={\lambda }_5=-10$. Above the $t\overline{t}$ threshold, $\mathcal{B}(S_R\to t\overline{t})$ rises rapidly to 100%.

Figure 6

Branching ratios for $S_I$ left panel ($S^{\pm }$ right panel) decay for parameter values ${\eta }_U=5$ and ${\eta }_D=1$. Above the $t\overline{t}$ threshold, $\mathcal{B}(S_I\to t\overline{t})$ rises rapidly to 100%.

Figure 7

Illustrative parameter points for $S_R$ decay modes, top four panels; $S_I$ decay modes, bottom left; and $S^{\pm }$ decay modes, bottom right. In all cases ${\eta }_U=0$.

Figure 8

Limits on $\mathcal{B}(S\to gg)$ from ATLAS [43] and CMS [42] searches for pair-produced resonances decaying to four jets as discussed in the text.