Topness Information & Topness Links at HealthHaven.com

	Flavour in particle physics v • d • e
	Flavour quantum numbers: Baryon number: B; Lepton number: L; Strangeness: S; Charmness: C; Bottomness: B′; Topness: T; Isospin: I or I3; Weak isospin: T or T3; Electric charge: Q; Combinations: Hypercharge: Y Y = (B + S + C + B′ + T); Y = 2 (Q − I3); ; Weak hypercharge: YW YW = 2 (Q − T3); X + 2YW = 5 (B − L); ; Flavour mixing CKM matrix; PMNS matrix; Flavour complementarity;

Topness (formerly also called truth), a flavour quantum number, is the number of top quarks (t) minus the number of top anti-quarks ( $\bar t$ ) that are present in a particle:

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

Top quarks have a topness of +1 and anti-top quarks have a topness of −1.

Topness is preserved under strong and electromagnetic interactions, but not under weak interaction. However the top quark is extremely unstable, with a half life under 10⁻²³ s, which is the required time for the strong interaction to take place. For that reason the top is never found to form any meson or baryon: by the time it can interact strongly it has already decayed to another flavor of quark (usually to a bottom quark).

This term is rarely used. Most physicists simply refer to "the number of top quarks" and "the number of top antiquarks".

[edit] See also

top quark

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