Rare meson decay through off-shell doubly charged scalars

The presence of charged scalars is almost inevitable in most of the beyond standard model scenarios. They are expected to be detected easily if they are there due to their electromagnetic charge. These charged scalars can be produced at the LHC and their decays may lead to interesting signals—multilepton final states, displaced vertices, etc. These charged particles also play crucial roles in low energy rare processes. Thus apart from the collider searches in low energy rare processes their presence can be smelled. Here, we have noted the impact of doubly charged scalars in rare meson decays. As the mesons are lighter these heavy scalars always appear off shell. Due to their off-shell structure the phase space is relatively complicated to deal with. In this paper we have supplemented a general proposal to compute these decays that involve off-shell doubly charged scalars. We have argued that our prescription can be used for any process involving off-shell heavy scalars. Using the prescribed method we have computed two possible meson decays: $M^{\pm }\to l_i^{\pm }{l}_j^{\pm }{M}^{\prime \mp }$, $M^{\pm }\to l_i^{\pm }{l}_j^{\pm }{l}_m^{\mp }{l}_n^{\mp }{M}^{\prime \pm }$. We have also estimated the numerical values of the branching ratios in different channels for different charged mesons.

Figure 1

Meson decay $M^{\pm }\to M^{\prime \mp }{l}_1^{\pm }{l}_2^{\pm }$ through the heavy doubly charged scalars: s-channel (left) and t-channel (right) diagrams.

Figure 2

Neutrinoless double beta decay ($0\nu \beta \beta$) diagram mediated by doubly charged scalar.

Figure 3

Charged meson decay $M^{\pm }\to M^{\prime \pm }{l}_1^{\pm }{l}_2^{\pm }{l}_3^{\mp }{l}_4^{\mp }$ through the heavy doubly charged scalars.