There’s a huge number of possible light quark/antiquark events, so it makes sense to distinguish these from tauon/antitauon events and “heavy” b-/anti-b-quark events.

In the case of three or four tracks one can use, that light don’t characteristically decay into one plus three tracks like the 𝛕⁺𝛕⁻ events. Additionally, they usually produce fewer neutrinos, so they typically have less missing energy. Furthermore, light quark/antiquark processes are usually less straight than 𝛕⁺𝛕⁻ events.

In the case of five to eleven tracks one can distinguish light quark processes from those with heavy b-quarks, because the light quark events are usually a lot straighter than b-/anti-b-quark events. Why that is the case is the easiest to understand by considering the b-/anti-b-quark production which is explained on the corresponding page.