Quark mixing vs neutrino mixing, mass eigenstates, weak states and detection

Question

I have some doubts regarding the CKM matrix in the quark sector and PMNS matrix in the leptonic sector. Let us call $(d^\prime, s^\prime, b^\prime)$ the weak basis for quarks and $(d,s,b)$ the mass basis in the quark sector. In the leptonic sector $\nu_e,\nu_\mu,\nu_\tau$ are the weak basis ans $\nu_1,\nu_2,\nu_3$ represent the mass basis.

1. All the weak processes involving quarks are written in terms of the mass basis. For example, $$d\rightarrow u,\hspace{0.5cm} d\rightarrow s$$ etc. But in the leptonic sector the weak processes involving neutrinos are written in terms of weak basis. Why is this difference? Does it mean the physical particles in the quark sector are the mass eigenstates and those in the leptonic sector are the weak states? Isn't it strange?

2. What about the crucial matter of production and detection of neutrinos and quarks? It is said that neutrinos are produced in one of the weak states and I presume they are also detected as weak state. But what happens in the quark sector? Processes like $d\rightarrow u$ or $d\rightarrow s$ seems to imply that quarks are produced in mass eigenstates.

3. If there is the phenomenon of oscillation of neutrino weak states, from $\nu_e\rightarrow \nu_\mu$ (say, for example), why is there no such oscillation observed in the quark sector form $d^\prime\rightarrow s^\prime$?

Answer 1

1) You can of course write down these amplitudes in any basis you choose, as long as you take into account matrix elements of the CKM and PMNS matrix.

2) There is indeed a difference here, neutrinos are produced exclusively by the weak interaction, whereas quarks can be pair produced by the strong (or electric) force, or produced by weak decays.

3) in principle hadronic states can oscillate, $K-\bar{K}$ and $B-\bar{B}$ oscillations have been studied in great detail. Also, interference effects in weak decays certainly exist. There are some difficulties, however, with observing''$d-s$'' oscillations: i) Quarks are confined, so the actual oscillation would have to be $\pi-K$. ii) But pions and kaons are (typically) produced as strong (mass) eigenstates. iii) The mass difference is quite large, and the oscillation length would be very short. iv) Kaons are unstable (not necessarily a problem, they live sufficiently long to observe kaon-anti-kaon oscillations).