Quarks

Fair enough, obviously these symmetries were trying to tell us something about the composition of hadrons. What? Well, needless to say, Gell-Mann did not immediately come up with a simple nuts-and-bolts assembly manual; instead, they developed an abstract mathematical description called analogous to the description of spin for electrons, . [If you're interested, the acronym stands for Simple Unitary group of order 2 or 3.] I won't attempt to elaborate, but you can see why something like this was needed - as for the component of spin, the projections of the three operators along God-only-knows what axes in God-only-knows what dimensions cannot have a continuum of possible values but only a fixed number of discrete or quantized values. What is actually refers to is totally unknown. Or, more properly, it refers to just what it says; if that means nothing to us, well, that's just because our empirical personal experience of the space of is so limited that we don't relate to it very well. What do ``normal'' space and time actually refer to?

Anyway, someone inevitably formulated a simpler instruction manual for assembling hadrons. This was to give the requisite properties to three (there are more now, but hold off on that) really fundamental component particles called `` quarks.'' All mesons are composed of a quark-antiquark pair whereas baryons are composed of three quarks held together by a `` superstrong'' force mediated by a new type of intermediary called `` gluons'' (g) [more cuteness, but who can argue...].

  
Table: The known (or suspected) ``generations'' of quarks All quarks have a ``baryon number'' as well as fractional electric charge because it takes 3 to make one baryon. The ``hypercharge'' of any particle is the sum of its baryon number and its strangeness: . For each quark there corresponds an antiquark of the same mass, spin, parity and isospin, but with opposite values of electric charge, strangeness, baryon number and hypercharge.

  
Figure: Upper left: the three lowest-mass quarks. Lower left: the corresponding antiquarks. Right: the spin- baryons. The (strangeness -3) was predicted by a ``quark content'' analysis and later found experimentally, convincing everyone that the model was correct.

• Colour
• Why Quarks are Hidden