I have a question regarding Figure 1 from this paper: https://cds.cern.ch/record/2859612/files/TOP-22-008-pas.pdf
How can a top quark decay into a top quark and a $W^{-}$ boson?
I have a question regarding Figure 1 from this paper: https://cds.cern.ch/record/2859612/files/TOP-22-008-pas.pdf
How can a top quark decay into a top quark and a $W^{-}$ boson?
It's a typo. The horizontal line should be a "b" with charge -1/3 rather than a "t" with charge +2/3. This is clear because the incoming "b" has emited a charge neutral gluon, and therefore remains a "b".