Direct searches of Type-III seesaw triplet fermions at high energy $$e^+e^-$$ e+e- collider

Abstract

Abstract The signatures of heavy fermionic isotriplets ($$\Sigma $$ Σ ) are probed through their direct production and subsequent decay at high energy electron–positron colliders. Unlike the case of LHC, the production process has strong dependence on the mixing of $$\Sigma $$ Σ with electron ($$V_{e}$$ Ve ), making the leptonic collider unique to fingerprint the presence of such mixing. We establish that pair production considered at $$\sqrt{s}=2$$ s=2 TeV can be employed to study both the cases of $$V_e=0$$ Ve=0 and of $$V_e\ne 0$$ Ve≠0 with $$\sim 100$$ ∼100 fb$$^{-1}$$ -1 luminosity, while the single production can probe the latter case with a few inverse femto barn luminosity at $$\sqrt{s}=1$$ s=1 TeV. Exploring the mass reach, both the single and pair productions are capable of probing $$\Sigma $$ Σ of mass close to the kinematic limits through selected channels. Investigating simultaneous limits on the $$M_\Sigma -V_e$$ MΣ-Ve parameter space, we identify suitable final states and their $$3\sigma $$ 3σ reach on $$V_e$$ Ve and $$M_\Sigma $$ MΣ at 300 (100) fb$$^{-1}$$ -1 luminosity in the case of pair (single) $$\Sigma $$ Σ production.