I have read a lot of questions on this site about neutrino absorption, and all of them mention that usually when a neutron transforms into a proton or vica versa, that is really an up quark transforms into a down quark or vica versa, a neutrino is absorbed (or emitted).
Now none of these say whether the word absorption is used as in fact the neutrino being absorbed by a specific particle, that is the neutron or the proton as a whole system, or just a quark (though in confinement), as a separate elementary particle.
Is it correct to view this as analogous to photon absorption, where a free electron cannot absorb a photon (except when accelerating in an external magnetic field), but it is really the atom/electron system that absorbs the photon.
Is it the same with a neutrino, where the whole neutron or proton (quark, antiquark, gluon sea) can only absorb the neutrino, and not the quark itself?
I have read this:
https://arxiv.org/pdf/0804.3899.pdf
And it is talking about quark-neutrino scattering (elastic).
https://en.wikipedia.org/wiki/Weak_interaction
This wiki site does not mention neutrino absorption, just emission in certain cases. Usually the process is described by a intermediary (virtual) W or Z bozon transforming into a neutrino and another lepton.
Question:
1.In neutrino absorption, what is it really that absorbs the neutrino?