In
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
, bottomness (symbol ''B′''; using a prime as plain ''B'' is used already for
baryon number
In particle physics, the baryon number (B) is an additive quantum number of a system. It is defined as
B = \frac(n_\text - n_),
where is the number of quarks, and is the number of antiquarks. Baryons (three quarks) have B = +1, mesons (one q ...
) or beauty is a
flavour quantum number reflecting the difference between the number of
bottom antiquarks (''n''
) and the number of
bottom quark
The bottom quark, beauty quark, or b quark, is an elementary particle of the third generation. It is a heavy quark with a charge of − ''e''.
All quarks are described in a similar way by electroweak interaction and quantum chromodynamic ...
s (''n''
) that are present in a particle:
:
Bottom quarks have (by convention) a bottomness of −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
Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and ...
(symbol ''Q'') of that quark (in this case, Q = −).
As with other flavour-related quantum numbers, bottomness is preserved under
strong
Strong may refer to:
Education
* The Strong, an educational institution in Rochester, New York, United States
* Strong Hall (Lawrence, Kansas), an administrative hall of the University of Kansas
* Strong School, New Haven, Connecticut, United ...
and
electromagnetic interactions, but not under
weak interaction
In nuclear physics and particle physics, the weak interaction, weak force or the weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, and gravitation. It is th ...
s. For first-order weak reactions, it holds that
.
This term is rarely used. Most physicists simply refer to "the number of bottom quarks" and "the number of bottom antiquarks".
References
*
Quarks
Flavour (particle physics)
{{particle-stub