Can neutrinos pass through a quark

[bland]

I am puzzled by the mechanism that enables neutrinos to be able to pass though many light years of lead without interacting with anything. I understand that they do not feel the strong force and that the weak force is slow to respond, but to travel straight though a 100 light year thick slab of lead, surely it not possible that they avoid everything. So what happens at the quantum level when a neutrino hits a quark square on? do they simply go straight through the quark?

 

[DrChinese]

Quarks are point particles (as are neutrinos), no intrinsic size. Their effective cross section is mostly a result of the virtual gluons being exchanged (the strong force). It wouldn't really be quarks anyway that stop neutrinos, it would be the surrounding atomic structure as a whole (a lone quark would do nothing to scatter a neutrino). There are cases in which it can absorb a neutrino in a "somewhat analogous" reverse nuclear reaction to what emits a neutrino in the first place.

http://authors.library.caltech.edu/33286/1/BAHpr64d.pdf
http://www.physics.ox.ac.uk/neutrino/Petyt/chapter2.pdf

 

[bland]

OK, thanks for that reply and the pdf's.

 

[ChrisVer]

Well, you shouldn't think of neutrinos as balls striking the quarks...
Things are way more complicated. Since interactions mainly occur by the mediation of force carriers, then if there is no force carrier there is no interaction, even if the particle goes through the other...Interactions are then connected to probabilities, with the weak being the less probable (because of the heavy gauge bosons).

 

[nikkkom]

So what happens at the quantum level when a neutrino hits a quark square on? do they simply go straight through the quark?

The same as when a photon hits another photon - nothing happens. They go through each other as if nothing was there.

Particles are not tiny ball bearings. Your intuition says "when things collide, they bounce off or otherwise interact ('rock shatters glass' etc)". Your intuition comes from your everyday experience with baryonic matter. In general, it's wrong: when things collide, they MAY interact, but don't necessarily interact.