Interaction between electron & neutron

[Denton]

Since a neutron has no charge and an electron is not involved in the strong nuclear force, does this mean that an electron has no interaction between a neutron? As in a very dense neutron star, would we expect that electrons could easily pass right though without being absorbed/deflected in any way?

 

[jtbell]

Neutrons are composite particles made up of quarks which are charged, so the electromagnetic interaction is not out of the picture. Also, electrons and quarks can interact via the weak interaction.

 

[Denton]

Yes but since the charge of each quark has become neutralised why would one expect there be any electromagnetic interaction even when the electron 'enters' the neutron? Also with the weak reaction, i thought those only happened when some sort of nuclear reaction took place, how does an electron interact with a neutron on this level?

 

[Renge Ishyo]

Both neutrons and electrons have mass so gravity will have an influence between the particles at the very least. Gravity is normally very weak compared to the electrostatic force, but if you had a very dense (massive) neutron star it seems reasonable that the gravitiational attraction between such a star and an electron can be quite large...

 

[Gokul43201]

Yes but since the charge of each quark has become neutralised why would one expect there be any electromagnetic interaction even when the electron 'enters' the neutron?

How has it become "neutralised"?

A neutron is a composite particle that is charge neutral, sort of in the same way that you are also a charge neutral object (made up of charged particles). But that doesn't mean an electron fired at you will not interact with your constituent (charged) particles.

PS: Incidentally, you share your username with the manufacturer of electron beam equipment.

 

[jtbell]

Note that the neutron has a nonzero magnetic moment, so it can interact with a magnetic field.

 

[BenTheMan]

Note that the neutron has a nonzero magnetic moment, so it can interact with a magnetic field.

It also has a spin, so they can couple to each other that way, too.

 

[Vanadium 50]

It also has a spin, so they can couple to each other that way, too.

That's not enough. A neutrino and photon both have spin, but they do not interact with each other.

JTBell is correct - the electron has a magnetic interaction with the neutron. He's also right that an electron can interact electrically with the quarks inside a neutron, although this is the scale at which the concept of a neutron behaving as a simple particle breaks down.

 

[Denton]

How has it become "neutralised"?

A neutron is a composite particle that is charge neutral, sort of in the same way that you are also a charge neutral object (made up of charged particles). But that doesn't mean an electron fired at you will not interact with your constituent (charged) particles.

Ive always expected this because a neutron does not have a slightly positive side or a slightly negative side as one would expect something being made of dissimilar charged components.

 

[malawi_glenn]

At high energies, the electron can "resolve" the components of the neutron (i.e. the quarks)

 

[humanino]

Ive always expected this because a neutron does not have a slightly positive side or a slightly negative side as one would expect something being made of dissimilar charged components.

It does. There is a non-trivial distribution of charge, not from left to right (unless you break left-right symmetry, by polarization or something), but from inside to outside.

 

[Vanadium 50]

To build on that a bit: if a neutron had a positive side and a negative side, this would be called it's electric dipole moment. This has been measured to be zero to exquisite precision - it's one of the best known numbers in subatomic physics. However, the inside of a neutron is measurably more positive than the outside.

Now we can ask ourselves what would happen if we scattered a variable energy beam of electrons at a pile of neutrons. First, at very low energies, they would interact magnetically with the whole neutron. As the energy increases, they would start to interact electrically with the negative halo and the positive core. As the energy increases further, they would start to interact with the constituent quarks (the quarks and, in a sense, their "nearby" gluons) and finally at the very highest energies they would interact with the bare current quarks.

 

[Denton]

Thanks for that :)