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Topness

From Biocrawler, the free encyclopedia.

Flavour in particle physics

Flavour quantum numbers

Y=B+S+C+B'+T
Q=I_z+Y/2
Q=T_z+Y_W/2
B-L conserved in the standard model

Related topics:

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".

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