Bottomness

Bottomness
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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 I_z Weak isospin: T or T_z Electric charge: Q Combinations: Hypercharge: Y Y = 2 (Q − I_z) Weak hypercharge: Y_W Y_W = 2 (Q − T_z) X + 2Y_W = 5 (B − L) Related topics: CPT symmetry CKM matrix CP symmetry Chirality

In physics, bottomness (also formerly called beauty) quantum number is the number of bottom anti-quarks ( $\bar b$ ) minus the number of bottom quarks (b) that are present in a particle:

$\tilde B = n_{\bar b} - n_b$

Bottom quarks have a bottomness of −1 and bottom anti-quarks of +1, so the bottomness sign agrees with its charge ( $- 1 / 3$ for b).

As with other flavor-related quantum numbers, bottomness is preserved under strong and electromagnetic interaction, but not under weak interaction. For first-order weak reactions, it holds that $|\Delta \tilde B| = 1$ .

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

See also