Topness

Topness(symbolT) ortruthis aflavour quantum numberthat represents the difference between the number oftop quarks(t) and number oftop antiquarks(t) present in a particle:

$T=n_{\text{t}}-n_{\bar {\text{t}}}$

By convention, top quarks have a topness of +1 and top antiquarks have a topness of −1. The term "topness" is rarely used; most physicists simply refer to "the number of top quarks" and "the number of top antiquarks".

Conservation

Like allflavour quantum numbers,topness is preserved understrongandelectromagnetic interactions,but not underweak interaction.However the top quark is extremely unstable, with ahalf-lifeunder 10⁻²³s, which is the required time for the strong interaction to take place. For that reason the top quark does nothadronize,that is it never forms anymesonorbaryon,so the topness of a meson or a baryon is always zero. By the time it can interact strongly it has already decayed to another flavour of quark (usually to abottom quark).

References

• Anchordoqui, L.;Halzen, F.(2009). "Lessons in Particle Physics".arXiv:0906.1271[physics.ed-ph].

Further reading

• Anchordoqui, L.;Halzen, F.(2009). "Lessons in Particle Physics".arXiv:0906.1271[physics.ed-ph].