Editing Baryon number (section)

== Baryon number vs. quark number ==
{{See also|Color charge}}

Quarks carry not only [[electric charge]], but also [[charge (physics)|charges]] such as [[color charge]] and [[weak isospin]]. Because of a phenomenon known as ''[[color confinement]]'', a [[hadron]] cannot have a net color charge; that is, the total color charge of a particle has to be zero ("white"). A quark can have one of three "colors", dubbed "red", "green", and "blue"; while an antiquark may be either "anti-red", "anti-green" or "anti-blue".<ref name="hyerphys">{{cite web |last=Nave |first=R. |author-link=Rod Nave |title=The Color Force |url=http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/color.html |access-date=May 29, 2021 |archive-date=August 20, 2007 |archive-url=https://web.archive.org/web/20070820075205/http://hyperphysics.phy-astr.gsu.edu/hbase/forces/color.html |url-status=live }}</ref>

For normal hadrons, a white color can thus be achieved in one of three ways: 
* A quark of one color with an antiquark of the corresponding anticolor, giving a [[meson]] with baryon number 0,
* Three quarks of different colors, giving a [[baryon]] with baryon number +1,
* Three antiquarks of different anticolors, giving an antibaryon with baryon number &minus;1.

The baryon number was defined long before the [[quark model]] was established, so rather than changing the definitions, particle physicists simply gave quarks one third the baryon number.

In theory, [[exotic hadron]]s can be formed by adding pairs of quarks and antiquarks, provided that each pair has a matching color/anticolor. For example, a pentaquark (four quarks, one antiquark) could have the individual quark colors: red, green, blue, blue, and antiblue. In 2015, the [[LHCb|LHCb collaboration]] at [[CERN]] reported results consistent with pentaquark states in the decay of [[bottom Lambda baryon]]s ({{nowrap|Λ{{su|p=0|b=b}}}}).<ref name="LHCb2015">
{{cite journal
 |author=R. Aaij et al. ([[LHCb|LHCb collaboration]])
 |year=2015
 |title=Observation of J/ψp resonances consistent with pentaquark states in Λ{{su|p=0|b=b}}→J/ψK<sup>−</sup>p decays
 |journal=[[Physical Review Letters]]
 |volume=115 |issue=7
 |pages=072001
 |doi=10.1103/PhysRevLett.115.072001
 |pmid=26317714
 |arxiv = 1507.03414 |bibcode = 2015PhRvL.115g2001A |s2cid=119204136
}}</ref>