# Anti particles: What exactly is inverted?

http://en.wikipedia.org/wiki/Antiparticle says "Corresponding to most kinds of particles, there is an associated antiparticle with the same mass and opposite electric charge." and What is anti-matter? goes along with that.

But.

Reading about the Standard Model I see several things sometimes called XXX-charge, like baryon-charge, lepton-charge - or baryon-number, lepton-number.

And as far as I see in the examples I found (but until now never in any definition I found) the anti particles have a negative XXX-charge/-number too.

So can you point to a list, what exactly is inverted in anti particles? (And why this list? Sure it has to do with the Standard Model, hasn't it? But Why? :)

-
Essentially a duplicate of this question. –  Qmechanic Aug 21 '12 at 21:45
Maybe, but not recognisably so. –  Falko Aug 22 '12 at 5:23

Charge is only the most familiar of the properties that are inverted between a particle and its antiparticle, but it's not the only one. So you should not consider "same mass and opposite electric charge" to be a definition of what an antiparticle is; it's merely a plain-English explanation.

A list of properties in which particles and antiparticles differ can be found on the Wikipedia page for flavor. In particular, they include

• Each of the six quark flavor quantum numbers (upness, downness, strangeness, charmness, bottomness, topness)
• Isospin, which is like a combination of upness and downness
• Baryon number, which is like a combination of all six quark flavor numbers
• Each of the three lepton flavor quantum numbers (electron number, muon number, tau number)
• Lepton number, which is like a combination of all three lepton flavors
• Weak isospin
• Electric charge
• Hypercharge, which is like a combination of weak isospin and electric charge
• Parity
• Chirality... sort of (let's just say that one's complicated)

As I've mentioned, some of these are just combinations of others, so you couldn't make a complete list of all the quantum numbers in which particles and their antiparticles differ, but you could list all the "fundamental" ones (the basis of the vector space of quantum number operators). I'm not sure I got them all here, but I can't think of any others off the top of my head.

-
"sort of (let's just say that one's complicated)" ::laughs:: Yep. Let's do that. –  dmckee Aug 22 '12 at 3:48
IIRC, the parity of a fermion is opposite to that of its antiparticle, but for a boson they are the same. –  Brian Bi Jan 1 at 4:42