topness

Topness (symbol T) or truth is a flavour quantum number that represents the difference between the number of top quarks (t) and number of top antiquarks () 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".