So, is it finally accepted that neutrinos (at least one of the species) has mass? I have been searching and all I found was a million different articles about that huge detector which may have found some which did.
If its the case, which one was it, and how much have physicists needed to change any of the standard model?
It’s been inferred that neutrinos have mass, by experiments that seem to indicate that the three kinds of neutrinos can turn into each other. According to the theories of particle physics, this can only happen if they have some non-zero rest mass.
AFAIK, no one has directly measured the mass of any neutrino. Myself, I usually wait for five years or so before accepting any new claim in either particle physics or cosmology.
If any of them has mass, they all three have mass, and the tau is heavier than the mu, which is heavier than the electron neutrino. The best estimate is that the electron neutrino has a mass of about 3 eV; for comparison, the lightest particle known to have mass, the electron, weighs in at 510998.902 eV. All measurements or estimates of the neutrino’s mass thus far include zero in the one-sigma error bars. Neutrino oscillation would require that the mass be nonzero, but so far as I know, oscillation hasn’t yet been proven.
Regardless of the neutrino’s mass or lack thereof, the Standard Model is completely safe. It’s not yet anywhere near being able to predict the mass of any particle, so it can’t be proven wrong, on that count. Right now, all the masses are input parameters, so this just means that folks would have to input “3 eV” instead of “zero”. Probably the most interesting implication of a nonzero neutrino mass is that it means that right-handed neutrinoes must exist, but we’re still not likely to find any of them.
The Sudbury Neutrino Observatory site http://www.sno.phy.queensu.ca/ has the press release, but also a description of the detector and the full text of the paper.
Tonite’s Nightline had a rather good story about the Sudbury neutrino observatory, and the implications that the recently announced results have on cosmology.
But I was disappointed by one thing:
[Sagan mode]
The astronomer they hosted for the live interview failed to address the preeminent feature that makes cosmology so fascinating.
Namely, that the properties of the largest things we can imagine - the structure and fate of the universe - are intimately linked with the properties of the smallest things we can conceive of: neutrinos and other subatomic partcles.
This convolution of biggest and smallest, the intimate association of macro and micro, the ouroboros-like symmetry of colossal and miniscule, is perhaps the most singly beautiful thing about modern science… something that even laymen can appreciate.
It’s almost spiritual. It is a premiere example of the underlying beauty of the universe, something so aesthetically pleasing that we can even point it out to fundamentalists to show them how, in their own terms, no matter how much we apply science and mathematics, the beauty of God’s design still shows through.
It never fails to awe me. In fact, sometimes, it brings me nearly to tears.
[/Sagan mode]
Actually, when I speak those things, I sound more like the Crocodile Hunter than Carl Sagan.