Spining of protons and its effect on stability of nucleus

1. Jun 13, 2014

shivakumar06

dear sir,
i heard that that proton spins about itselfand this helps in stability of nucleus. i also heard from the a friend that neutron has a proton and electron within it. this electron moves out from neuton making it proton and entering proton to form a neutron. sir i need to know if it is true and and many other interesting facts about nucleus and protons and neutrons. please guide me.

2. Jun 13, 2014

ChrisVer

1. The spin doesn't mean any spin about itself- it's just an intrinsic quantum number so it's better to avoid such visualizations of it (although it looks like angular momentum). The stability of the nuclei- I don't get how the proton spin affects that... In general the proton spin could allow or forbid some transitions of an excited nucleus state to another (because spin is coupled to electromagnetic forces). Of course the spin plays a role in the energy levels of a nuclei because it exists in the interactive hamiltonian.
For your second question, that is totally wrong...
The fact that the neutron's charge distribution is positive within a certain radius and negative outside doesn't mean that a neutron is a proton+electron..the only analogy I've seen of that, is that of pions rather than electrons and it's still an analogy and doesn't reflect any truth... Neither the fact that an electron can be captured by a proton to give a neutron means that thing for the neutron...

3. Jun 13, 2014

Drakkith

Staff Emeritus
This is true in that the proton's quarks have the equivalent of orbital angular momentum, but I don't know how it affects the stability of the nucleus.

This is not true. Protons are composed of 2 up quarks and 1 down quark. The two up quarks have + 2/3 charge, while the down quark has -1/3 charge. Adding them up gives the proton a charge of +1. A neutron, on the other hand, is composed of 2 down quarks and 1 up quark. Adding the charges together we get a net charge of 0, making the neutron neutral overall.

Note that we can make neutrons in particle colliders without having to have protons and electrons. The fact that a proton and an electron can "combine" and form a neutron is simply the result of charge and mass conservation. The electron disappears and the energy and charge is used to convert one one of the up quarks to a down quark (a down quark is heavier than an up quark, so to convert an up quark into a down quark, energy and charge are required in order to satisfy conservation laws).

4. Jun 14, 2014

kurros

It is an entirely separate matter. If you take a proton, and change the quark spin or orbital angular momentum, then we don't call that thing a proton anymore, we call it a different particle (e.g. Δ+). This is because changing the internal angular momentum changes the internal energy by a lot, i.e. changes the mass. Anyway they are very unstable so no long-lived nuclei will contain such a particle.

5. Jun 14, 2014

Drakkith

Staff Emeritus
Hmmm... I was reading on the proton spin crisis and how a significant portion of the angular momentum comes from something other than the quark's spin. Is that correct?

6. Jun 14, 2014

kurros

Well, I am not super familiar with that issue, but certainly the proton is not just a bag of 3 quarks. It is a soup of strongly-interacting junk. There are lots of "sea" quarks and gluons in there, as well as the three "valence" quarks. So the spin and angular momentum from all that junk contributes as well.

7. Jun 15, 2014

ChrisVer

I think the calculations for the gluon and sea quarks contribution in the proton spin are already calculated and give zero result... that's why the spin-problem arises and people look into COMPASS.

8. Jun 15, 2014

Bill_K

9. Jun 15, 2014

HeavyMetal

Your friend may have been talking about beta decay and electron capture. Beta decay is the simultaneous emission of an electron and an electron antineutrino, converting a neutron into a proton ($n^{0} \longrightarrow p^{+}+e^{-}+\overline{\nu}_{e}$). Electron capture is the collision between an electron and a proton making a neutron and an electron neutrino ($e^{-}+p^{+} \longrightarrow n^{0}+\nu_{e}$).

10. Jun 15, 2014

Bill_K

shivakumar06, it helps the discussion greatly if you have a specific reference to cite, either a book or something accessible on the web.

"I heard that", and "a friend told me" could mean almost anything!

11. Jun 16, 2014

Staff: Mentor

There are many types of spin involved, the statement is too unclear for a specific answer.

One aspect not mentioned before: due to spin, protons (and neutrons) are fermions and not bosons. Bosons would form nuclei that would look completely different.

This is wrong.

-> books about nuclear and particle physics

12. Jun 17, 2014

shivakumar06

dear sir
i would like to thank you for you guidance and i request you to tell me about books and website on nuclear and particle physics.