Shedding light on top partner at the LHC

We investigate the sensitivity of the 14 TeV LHC to pair-produced top partners ( T ) decaying into the Standard Model top quark ( t ) plus either a gluon ( g ) or a photon ( γ ). The decays T → tg and T → t γ can be dominant when the mixing between the top partner and top quark are negligible. In this case, the conventional decays T → bW , T → tZ , and T → th are highly suppressed and can be neglected. We take a model-independent approach using effective operators for the T - t - g and T - t -γ interactions, considering both spin- 1/2 and spin- 3/2 top partners. We perform a semi-realistic simulation with boosted top quark tagging and an appropriate implementation of a jet-faking-photon rate. Despite a simple dimensional analysis indicating that the branching ratios BR( T → t γ) ≪ BR( T → tg ) due to the electric-magnetic coupling being much smaller than the strong force coupling, our study shows that the LHC sensitivity to TT→ ttγ g is more significant than the sensitivity to TT→ tt gg . This is due to much smaller backgrounds attributed to the isolated high- p T photon. We find that with these decay channels and 3 ab −1 of data, the LHC is sensitive to top partner masses m T ≲ 1 . 4-1 . 8 TeV for spin- 1/2 and spin- 3/2 top partners, respectively.