Shedding light on top partner at the LHC
Haider Alhazmi (Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, U.S.A., Department of Physics, Jazan University, Jazan, 45142, Saudi Arabia); Jeong Kim (Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, U.S.A.); Kyoungchul Kong (Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, U.S.A.); Ian Lewis (Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, U.S.A.)
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 → tγ 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- $$ \frac{1}{2} $$ and spin- $$ \frac{3}{2} $$ 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 → tγ) ≪ 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 $$ T\overline{T}\to t\overline{t}\gamma g $$ is more significant than the sensitivity to $$ T\overline{T}\to t\overline{t} gg $$ . 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- $$ \frac{1}{2} $$ and spin- $$ \frac{3}{2} $$ top partners, respectively.
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