# Oscillations: Neutral Kaon vs neutrino

• Dmitry67
In summary, the conversation discusses the concept of particle and mass eigenstates in relation to neutrinos and quarks. It is explained that while we detect mass eigenstates of neutrinos, they are actually a mixture of weak eigenstates. Similarly, quarks have different mass and weak eigenstates. The conversation also mentions that we observe superpositions in both cases, but the time scales and interactions are different. This is due to the weak interaction, which is what allows us to "observe" these superpositions.

#### Dmitry67

I understand that
$$K_l = \frac{d\bar{s} + s\bar{d}}{\sqrt{2}}$$
$$K_s = \frac{d\bar{s} - s\bar{d}}{\sqrt{2}}$$
This happens because $$K_0$$ is oscillating into its own antiparticle.
My question is, why the same is not applicable to the neutrinos? They do oscillate. So instead of ‘pure’ e, mu, tau neutrinos we do not observe superposition?

We detect mass eigenstates of neutrinos, but a mass eigenstate is a mixture of weak eigenstates. Similar for quarks, their mass and weak eigenstates are not the same.

We DO observe superpositions; we observe one of three mass eigenstates, each of which is a linear superposition of flavors.

In each case, the mass eigenstate propagates, but the particle eigenstate (d sbar or
say e-neutrino) interacts in the weak interaction. The time scales are different.
When you say "observe" that is the weak interaction.

clem said:
In each case, the mass eigenstate propagates, but the particle eigenstate (d sbar or
say e-neutrino) interacts in the weak interaction. The time scales are different.
When you say "observe" that is the weak interaction.

that is correct, i mixed them up. Sorry OP

ansgar said:
that is correct, i mixed them up. Sorry OP

So your thoughts are in superposition? :)

Thank you