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Register a new userProbing a new decay of vector-like top partner mediated by heavy Majorana neutrino via single production
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Models beyond the Standard Model have been proposed to simultaneously solve the problems of naturalness and neutrino mass, in which heavy Majorana neutrinos and vector-like top partners are usually predicted. A new decay channel of the top partner mediated by the heavy Majorana neutrino can thus appear: $Tto b,W^{+}to b,ell^{+}ell^{+}qbar{q}$. We study in this paper the observability of this decay process through single production of the top partner at the 14 TeV LHC: $ppto T/bar{T}$+jets$to b/bar{b}+mu^{pm}mu^{pm}$+jets. $2sigma$ exclusion bounds on the top partner mass and mixing parameters are given by Monte-Carlo simulation, which surpass those from the search through VLT pair production in the mass range of $m_{T}>1.3$ TeV.
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We first build a minimal model of vector-like quarks where the dominant Higgs boson production process at LHC -- the gluon fusion -- can be significantly suppressed, being motivated by the recent stringent constraints from the search for direct Higgs production over a wide Higgs mass range. Within this model, compatible with the present experimental constraints on direct Higgs searches, we demonstrate that the Higgs ($h$) production via a heavy vector-like top-partner ($t_2$) decay, $pp to t_2 bar t_2$, $t_2to t h$, allows to discover a Higgs boson at the LHC and measure its mass, through the decay channels $hto gammagamma$ or $hto ZZ$. We also comment on the recent hint in LHC data from a possible $sim 125$ GeV Higgs scalar, in the presence of heavy vector-like top quarks.
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