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Adam

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Registered Senior Member
Hello all. I've been reading up a bit on quarks, leptons, all that stuff. Now with quarks we have up, down, strange, charm, top, and bottom, with fractional charges. Each positive-sounding one is 2/3 , each negative-sounding one is 1/3, and together I assume that means one of each makes them electrically neutral (top + bottom = neutral or no charge). I think that's correct.

Anyway, for each there is also, I hear, an anti-particle which is the same except for having opposite charge. This is what I'm getting from the Particle Adventure website. Does this mean an anti-bottom-quark is basically a top quark, meaning it has 2/3 charge? If so, why call it an anti-bottom-quark instead of a top quark?

Now, I'm sure I'm missing something there. They don't go into a lot of detail. So clarification would be welcome.

Thanks.
 
Oh, do they mean that they have 2/3 and 1/3 positive charge, making them in general positive? And the anti-particles of each would have 2/3 and 1/3 negative instead, making the whol set of anti-particles negative?
 
Adam

If an up quark has charge -1/3 and a down has +2/3 an anti-up has charge +1/3 and an anti-down -2/3. I may have my ups and downs the wrong way.

So a proton is made of an udd = -1/3+2/3+2/3 = 1 a neutron is made of an uud = -1/3-1/3+2/3 = 0.
 
Can you recommend a good book on all this which may be available in Australia? Something for beginners yet explaining everything. (I don't ask for much. :p )
 
Also: Charge is not the only thing which is different between matter and antimatter. Other quantum numbers are also different.
 
Re: Adam

Originally posted by thed
If an up quark has charge -1/3 and a down has +2/3 an anti-up has charge +1/3 and an anti-down -2/3. I may have my ups and downs the wrong way.

So a proton is made of an udd = -1/3+2/3+2/3 = 1 a neutron is made of an uud = -1/3-1/3+2/3 = 0.
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Wouldn't the up quark have a charge of +1/3, not -1/3? Or is it:

Particles
up +2/3
top +2/3
charm +2/3
down +1/3
bottom +1/3
strange +1/3

Anti-Particles
anti up -2/3
anti top -2/3
anti charm -2/3
anti down -1/3
anti bottom -1/3
anti strange -1/3
 
Adam:

A few of those are wrong. I think, for example, the up quark is +2/3 and the down is -1/3. Two ups and a down make a proton with charge +1. Two downs and an up make a neutron with charge 0.
 
Originally posted by James R
Adam:

A few of those are wrong. I think, for example, the up quark is +2/3 and the down is -1/3. Two ups and a down make a proton with charge +1. Two downs and an up make a neutron with charge 0.
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So if you get an up and a down together, they end up with a charge of 1/3?
 
Originally posted by Adam
So if you get an up and a down together, they end up with a charge of 1/3?
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This can't happen. You can only get combinations of three quarks, called a baryon, with integral charge -- or a combination of one quark and its antiquark, called a meson, with zero charge.

- Warren
 
So, you have have, for example:

up, top, down = 2/3 + 2/3 - 1/3 = 1

or:

top, anti-top = 2/3 - 2/3 = 0

And baryons make up the positively charged protons to which we attach an electron, which balances out the charge?
 
Originally posted by Adam

And baryons make up the positively charged protons to which we attach an electron, which balances out the charge?
Click to expand...

quarks make up the proton. not baryons. a proton is a baryon. baryons make up the nucleus.
 
Originally posted by Adam
So, you have have, for example:

up, top, down = 2/3 + 2/3 - 1/3 = 1

or:

top, anti-top = 2/3 - 2/3 = 0

And baryons make up the positively charged nucleus to which we attach an electron, which balances out the charge?
Click to expand...


So if I change it to this, I'm on the right track?
 
Originally posted by Adam
So if I change it to this, I'm on the right track?
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Yes, except that most baryons are not stable. Up, top, down, for example, is not stable. The only two baryons which are stable are the proton and neutron, uud and udd, respectively.

- Warren
 
Can you recommend a good book on all this which may be available in Australia? Something for beginners yet explaining everything. (I don't ask for much.)
Click to expand...
All of this meaning particle physics? Or all of this as in science in general for laymen?

If the latter then you might try Brian Greene "The Elegant Universe", and, John Gribben's "In Search of Schrödinger's Cat" and "Schrödinger's Kittens". They're all at aimed at laymen (they're all good reads in any case :))
 
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