# The Naked Scientists Forum

#### MichaelS

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« on: 01/10/2009 16:53:29 »
I have a couple of questions. Please excuse if I make horrible newbie "I'm not a physicist" types of errors when I ask.

question: are color charge, and charge the same thing when it comes to describing Hadrons?
question: are color charge, charge (if it's different than color charge), and spin all related to each other in some way. another way of asking this, is "spin" independent of color charge?

tia

m

[MOD EDIT - PLEASE PHRASE YOUR POST TITLES AS QUESTIONS, IN LINE WITH OUR FORUM POLICY. THANKS, CHRIS]
« Last Edit: 02/10/2009 08:09:26 by chris »

#### JP

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #1 on: 01/10/2009 17:16:46 »
They're all different things and are independent.

Charge describes how strongly a particle interacts via the electromagnetic force.

Color charge describes how strongly a particle interacts via the strong force.

Spin is another intrinsic property of particles that works similar to angular momentum, which is a property of rotating objects (hence it's called spin).  However, the particles are not actually "spinning," it's just that the mathematics work out that way.

You can come up with devices that use both spin and charge to do useful things.  If you have a charged particle with spin, you generate a tiny magnet.  I know this has been applied in magnetic storage devices and in MRI imaging.

#### Mr. Scientist

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #2 on: 01/10/2009 20:53:52 »
They're all different things and are independent.

Charge describes how strongly a particle interacts via the electromagnetic force.

Color charge describes how strongly a particle interacts via the strong force.

Spin is another intrinsic property of particles that works similar to angular momentum, which is a property of rotating objects (hence it's called spin).  However, the particles are not actually "spinning," it's just that the mathematics work out that way.

You can come up with devices that use both spin and charge to do useful things.  If you have a charged particle with spin, you generate a tiny magnet.  I know this has been applied in magnetic storage devices and in MRI imaging.

Incorrect.

Spin is not a physical spin. It's actually an angular momentum.

#### JP

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #3 on: 01/10/2009 22:20:17 »
Uh... I said it wasn't physically "spinning."  However, it is not angular momentum.  For one thing, the total angular momentum of a fundamental particle can take on an infinite number of values, the spin number (the analogue of total angular momentum) is fixed.

#### Mr. Scientist

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #4 on: 01/10/2009 23:20:55 »
Trust me, angular momentum has prety much re-emphasized what spin physically-is.

#### MichaelS

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #5 on: 02/10/2009 00:17:15 »
Charge describes how strongly a particle interacts via the electromagnetic force.

Color charge describes how strongly a particle interacts via the strong force.

thank you thank you!

ok. i just read that color force is what holds the quarks together to form a proton/neutron and that the strong force is considered a residual of that force. As a residual of color force, strong force is what holds protons and neutrons together. is that correct?

also, the electromagnetic force operates to hold atoms together correct. So where the strong force holds neutrons and protons together, the electromagnetic force holds atomic nuclei and electrons together?

and where is the weak force in all this.

m

#### JP

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #6 on: 02/10/2009 01:48:05 »
i just read that color force is what holds the quarks together to form a proton/neutron and that the strong force is considered a residual of that force. As a residual of color force, strong force is what holds protons and neutrons together. is that correct?

also, the electromagnetic force operates to hold atoms together correct. So where the strong force holds neutrons and protons together, the electromagnetic force holds atomic nuclei and electrons together?

and where is the weak force in all this.

That's all correct to the best of my knowledge, though I'm not an expert in this area of physics.

The weak force only comes up in special situations, such as beta decay, which is where a proton turns into a neutron and spits out an electron.  It doesn't hold the nucleus together or hold atoms together.

There's also a concept of "electroweak unification" which says that at high energies, the electromagnetic and weak forces become one unified force, but I only know a little about how that works.

#### MichaelS

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• Posts: 12
##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #7 on: 02/10/2009 02:28:05 »
i just read that color force is what holds the quarks together to form a proton/neutron and that the strong force is considered a residual of that force. As a residual of color force, strong force is what holds protons and neutrons together. is that correct?

also, the electromagnetic force operates to hold atoms together correct. So where the strong force holds neutrons and protons together, the electromagnetic force holds atomic nuclei and electrons together?

and where is the weak force in all this.

That's all correct to the best of my knowledge, though I'm not an expert in this area of physics.

thanks. so how many colors of quarks are there?
also, how many different types of charge are there?

m

#### MichaelS

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #8 on: 02/10/2009 02:41:14 »
ok wait. this website says quarks have both color and charge

quarks carry fractional charges. is the addition of these charges what determines the charge on the resulting hadron?

m

#### JP

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##### Re: What are colour, charge and spin when talking about hadrons?
« Reply #9 on: 02/10/2009 02:45:18 »
There's 3 colors and 2 types of charge (the familiar positive and negative).

And yes, it is the addition of the quark's fractional electric charges that gives a hadron its electric charge.

#### Vern

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« Reply #10 on: 02/10/2009 12:32:30 »
ok wait. this website says quarks have both color and charge

quarks carry fractional charges. is the addition of these charges what determines the charge on the resulting hadron?

m
This is from the theory of Quantum Electro Dynamics and it works very well. But there is a way to define all the forces within the electromagnetic force. Richard Feynman wote about QED in his "QED the stange theory of light and matter".

Edit: On second thought the quoted text looks more like QCD which is similar to QED but studied by different advocates I think. QED only uses one charge value while QCD uses three. I suspect that these separate theories will eventually evolve into just one that more resembles QED.
« Last Edit: 02/10/2009 13:40:40 by Vern »

#### MichaelS

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« Reply #11 on: 02/10/2009 15:48:24 »

[MOD EDIT - PLEASE PHRASE YOUR POST TITLES AS QUESTIONS, IN LINE WITH OUR FORUM POLICY. THANKS, CHRIS]
[/quote]

will do. sorry

#### MichaelS

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« Reply #12 on: 02/10/2009 15:50:03 »
ok so one last question. quantum numbers are used a a short hand to describe the "state" of a particle correct. Am I getting this wrong or are quantum numbers just a fancy pants name for integers? Particle states are "discrete" (and not continuous) and so therefore we use "integers" (i.e. quantum numbers) to describe.

m

#### JP

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« Reply #13 on: 02/10/2009 16:15:20 »
ok so one last question. quantum numbers are used a a short hand to describe the "state" of a particle correct. Am I getting this wrong or are quantum numbers just a fancy pants name for integers? Particle states are "discrete" (and not continuous) and so therefore we use "integers" (i.e. quantum numbers) to describe.

Basically, yes.  Sometimes you use funny names such as in the case of color charge, or spin "up" or "down," but they're just labels for discrete things.