View source for Bottomness

{{Short description|Term  used in physics to refer to the number of bottom quarks}}
{{Flavour quantum numbers}}
In [[physics]], '''bottomness''' (symbol '''''B&prime;'''''; using a prime as plain ''B'' is used already for [[baryon number]]) or '''beauty''' is a [[Flavour (particle physics)|flavour quantum number]] reflecting the difference between the number of [[bottom antiquark]]s (''n''<sub>{{SubatomicParticle|Bottom antiquark}}</sub>) and the number of [[bottom quark]]s (''n''<sub>{{SubatomicParticle|Bottom quark}}</sub>) that are present in a particle:
:<math> B^\prime = -(n_b - n_{\bar b})</math>

Bottom quarks have (by convention) a bottomness of &minus;1 while bottom antiquarks have a bottomness of +1. The convention is that the flavour quantum number sign for the quark is the same as the sign of the [[electric charge]] (symbol ''Q'') of that quark (in this case, Q&nbsp;=&nbsp;&minus;{{frac|1|3}}).

As with other flavour-related quantum numbers, bottomness is preserved under [[strong interaction|strong]] and [[electromagnetic interaction]]s, but not under [[weak interaction]]s. For first-order weak reactions, it holds that <math>\Delta B^\prime = \plusmn 1</math>. 

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

==References==
* {{cite arXiv
 |last1=Anchordoqui  |first1=L.
 |last2=Halzen |first2=F.
 |authorlink2 = Francis Halzen
 |year=2009
 |title=Lessons in Particle Physics
 |eprint=0906.1271
 |class=physics.ed-ph
}}

[[Category:Quarks]]
[[Category:Flavour (particle physics)]]


{{particle-stub}}