Neutrons

[Little Bang]

How does the sun turn two up Quarks and one down Quark into two down Quarks and one up Quark?

[Erasmus00]

The weak interaction (in particular W bosons) couples down quarks to up quarks. What happens is that one of the up quarks flips to a down quark, emitting a W boson. The W boson then decays to a lepton and an anti-lepton neutrino (i.e. electron+electron anti-neutrino or muon+muon antineutrino).

-Will

[Little Bang]

Good answer Will. Right out of the book. Read the thread in philosophy of science ( The Box )

[Erasmus00]

Good answer Will. Right out of the book. Read the thread in philosophy of science ( The Box )

 

What answer did you expect? If you ask a question on a science site, expect a scientific answer (i.e. the answer backed by a decade of experiment).

[Little Bang]

No your right Will. You give the answer I expected. I have some reservations about the answer, one being that when the up quark flips to a down quark a W boson is emitted that has a mass of one hundred times the mass of the proton. I'm sure there is an explanation of how it acquires this extra mass.

[Little Bang]

One more question while I wait. My understanding may be wrong about a particle collider. Doesn't the collision of particles occur in a cloud chamber and the mass and charge of any resulting particle or particles is determined by their trajectory in a magnetic field?

[Erasmus00]

No your right Will. You give the answer I expected. I have some reservations about the answer, one being that when the up quark flips to a down quark a W boson is emitted that has a mass of one hundred times the mass of the proton. I'm sure there is an explanation of how it acquires this extra mass.

 

The answer is the energy/time uncertainty (more or less). The W boson doesn't last very long, it decays quickly into an electron/antielectron neutrino. In very short times, systems can have very large fluctuations in energy.

 

As to particle accelerators, more modern silicon trackers take the place of cloud chambers, but particles are still identified by their mass/charge via their reaction to magnetic fields.

-Will

[Little Bang]

If your satisfied with that answer then I see no reason for me to keep asking questions.

[Erasmus00]

If you really want to get at the heart of the answer, it may help to learn some quantum mechanics. To give a more thorough answer, one of the weird things about quantum mechanics is that there measurable quantities are represented as operators, and so they might not commute (i.e. AB may not be the same as BA). This comes just form the mathematical structure of representing things in a Hilbert space. I'm not sure anyone knows WHY this is the correct formalism, but experiment indicates it has.

 

This non-commutation leads to uncertainties, for instance, between momentum and the variable its conjugate to:

 

[math]\delta x \delta p_x \propto i\hbar [/math]

 

Now, when we go to relativity, momentum has four components, the fourth being time. So we expect one more relationship

 

[math]\delta t \delta E \propto i\hbar [/math]

 

This allows for the creation of "virtual" W bosons. This uncertainty shows up mathematically in the propagator: W bosons (all bosons, for that matter) have a propagator of the form

 

[math]\int d^4 p \frac{1}{p^2 - m^2}e^{ip\cdot x} [/math]

 

Here p and x are four vectors. For long lifetimes, the only part of the integral that matters is the p = m pole. For short lifetimes, off-pole contributions matter. These are "virtual."

 

Is this a better answer?

[froggy]

:Dspeaking of neutrons;

 

A neutron walks into a bar. He starts to sit down and the barkeep comes over,

 

Say, arnt you a Neutron? he asks.

 

The neutron says proudly, why yes I am, thanks for noticing.

 

The bartender asks, so what can I get you?

 

Well, Im so small and dont carry around alot of money, how much is it for a bottle of beer? the neutron says.

 

Barkeep smiles and says, for you? No charge!

[Little Bang]

What particle mediates charge? Surely it is some particle other than the quarks since that leaves me scratching my head as to an explanation for the charge on the electron.

[Erasmus00]

What particle mediates charge? Surely it is some particle other than the quarks since that leaves me scratching my head as to an explanation for the charge on the electron.

 

Photons mediate electromagnetic charges. Gluons mediate strong nuclear force. W and Z bosons mediate the weak nuclear force.

[Little Bang]

Eras, I bet everyone who reads your explanation of charge is ecstatic that you have elucidated their understanding of why the electron and quarks have charge. Slam your hand down on the SM Bible and shout how can you not understand it's in the book.

[arkain101]

A proton picks up a hooker and takes her home.

 

The proton asks are you sure you don't have HIV?

 

She replies, Im positive!

 

The proton knowing its illeagle to pay this hooker for loving Replies: I am so confused, but I can bet there is going to be some kind of a charge for this.

[Erasmus00]

Eras, I bet everyone who reads your explanation of charge is ecstatic that you have elucidated their understanding of why the electron and quarks have charge.Slam your hand down on the SM Bible and shout how can you not understand it's in the book.

 

You didn't ask why things are charged, you asked what particle mediated charge. I feel more and more as if you ask questions only to disparage the answer. If you wish to continue to get answers, you should consider a touch of courtesy.

 

To get into the realm of why things have the charges/hypercharges they do, you have to move beyond the standard model. So far, I would argue that grand unified theories offer the most compelling explanations of the charges. As Glashow and Georgi pointed out, he hypercharges of the standard model fit nicely into a fundamental representation of SU(5). So things have the charges they do because the forces we know are echoes of one entity.

[Little Bang]

OK, let me rephrase the question. What is charge? How is it achieved by an up quark or down and the electron?

[CraigD]

What is charge? How is it achieved by an up quark or down and the electron?

In particle physics, electric charge, usually called just charge, is the property a particle must have to interact via the electromagnetic interaction, one of the Standard Model’s 3 fundamental interactions.

 

The up quark has a charge of +2/3, the down, -1/3. So a hadron (a composite particle consisting of bound quarks) containing a u, u, and d quark has charge 2/3 +2/3 -1/3 = 1, and is a proton, while one containing a u, d, and d quark has charge 2/3 -1/3 -1/3 =0, and is a neutron.

 

The electron is a fundamental particle with charge -1.

 

Because both quarks and electrons have charge, they can interact via the electromagnetic interaction. On an atomic scale, this interaction is most significant, explaining most of observed reality on this scale, such as the physical nature of everyday matter and laws of chemistry.

 

There are many other properties of quarks and much quantum weirdness about how they interact with one another to be bound into hadrons, and interact with electrons, but accounting for the charge of these particles is pretty simple, and can be gleaned from many textbooks and websites, such as the wikipedia links in this post.