For Anyone Interested: A Sixty Symbols Video on the Recent Nobel Prize

Morbert

tl;dw

Models of the sun predicted lots of neutrinos hitting earth. Scientists only observed a few.

Either the model was wrong or neutrinos were turning into other, undetected kinds.

It turns out the latter was the case (which also means neutrinos must have mass). The prize was awarded for discovering this.

Labarbapostiza

Morbert wrote: »

It turns out the latter was the case (which also means neutrinos must have mass). The prize was awarded for discovering this.

Why do the neutrinos need mass to change flavour?

Labarbapostiza

Morbert wrote: »

It turns out the latter was the case (which also means neutrinos must have mass).

Mass in what sense?

Nearly all the mass of a Proton is gluons binding the quarks.

What are they on about?

Morbert

Mass in what sense?

The uncertainty principle which applies to position and momentum also applies to neutrino mass and neutrino type. I.e. If the neutrino wavefunction is in a state with a definite type, it must be in a superposition of mass states.

E.g. The electron neuturino wavefunction |e>, when written in terms of mass states (|m1>,|m2>,|m3>) is

|e> = a|m1> + b|m2> + c|m3>

where a,b,c are just numbers or "amplitudes".

Now, what is interesting is, if the masses m1, m2, and m3 associated with the mass states are different, the amplitudes a,b, and c change with time. If the amplitudes change, then we can no longer say the wavefunction is a state with a definite type, and so even though a neutrino starts as an electron neutrino |e>, there is a chance that we could observe a tau neutrino, and hence record |t>.

If all the mass states were the same (e.g. m1 = m2 = m3 = 0), then the amplitudes would not change, and hence a definite electron neutrino |e> would remain a definite electron neutrino forever.