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Reshma
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Do neutrinos have mass and spin?
Reshma said:Do neutrinos have mass and spin?
Jake said:What would they have been if they had no mass anyway, just another form of electromagnetic wave?
This seems like an awfully large upper limit. Do you have a reference?dextercioby said:They definitely have spin.As for mass,apparently there are no sources left which indicate zero mass.
To quote from the booklet from PDG,dating July 2004
[tex] m_{\nu_{e}}<3eV [/tex]
[tex] m_{\nu_{\mu}}<0.19MeV [/tex]
[tex] m_{\nu_{\tau}}<18.2MeV [/tex]
I'm not at all sure there was much of a time difference ... the photons 'first' detected were well after the star had gone SN (when someone in NZ or Australia actually noticed there was a star in the LMC that they didn't recognise). In any case, the neutrinos would escape the SN before EM, because the (dying) star becomes transparent to neutrinos as soon as the shock wave gets just above the core ... that wave takes some time to reach the surface of the star, when the EM finally breaks loose.kirovman said:I was under the impression that neutrinos from supernova reached the Earth before the photons did...because the photons are slowed by the gases and plasmas of space, and neutrinos rarely interact.
Forgive me if I'm wrong, this is something I learned about 4 or 5 years ago, so it's not fresh.
Some scientists were doing an experiment to measure the weak force or prove the existence of their mediator particle, I believe they used an underground reservoir of Chlorine or a compound of it. Anyway, they detected the influx of neutrinos a few hours before they observed a supernova.
So maybe they have mass, but they still seem to travel pretty fast.
Trouble with neutrinos, it's difficult to observe them. They were originally theorized to conserve energy in the weak interactions.
Andrew Mason said:This seems like an awfully large upper limit. Do you have a reference?
This source seems to put the sum of all three rest masses at less than .71 eV: http://xxx.lanl.gov/PS_cache/hep-ph/pdf/0302/0302191.pdf
AM
dextercioby said:To quote from the booklet from PDG,dating July 2004
When I asked for the reference, I meant: where can I find it?dextercioby said:Which part was it unclear??This one??
An object with mass cannot travel at c; a massless particle must travel at c. 'Weighing' neutrinos is very difficult to do, esp for the mu and tau kinds. Until neutrino oscillation was confirmed (observations and experiments), we couldn't say whether neutrinos have mass; now we can say that at most only one flavour can be massless. However, like all 'conclusions' in science, this is tentative, and assumes that several theories are good representations of 'reality' (whatever that is).Enos said:Close to the speed of light requires mass no? At the speed of light is the classification of massless no?
Andrew Mason said:When I asked for the reference, I meant: where can I find it?
AM
taeth said:mνe < 2.5 eV
νμ < 170 keV
ντ < 18 MeV
This is what I always thought it was...
These are not figures for rest mass. They represent relativistic mass. The Wikipedia page you referred to: http://en.wikipedia.org/wiki/Neutrino makes this clear:taeth said:mνe < 2.5 eV
νμ < 170 keV
ντ < 18 MeV
Andrew Mason said:These are not figures for rest mass. They represent relativistic mass.
The figures provided refer to solar neutrinos, I believe. They are expressed in relativistic mass (in units of eV/c^2).jtbell said:They can't represent relativistic mass. Relativistic mass depends on energy. A neutrino with an energy of 50 GeV, such as have been produced in accelerator experiments, has a relativistic mass of 50 GeV/c^2.
Neutrinos are subatomic particles that are electrically neutral and have an extremely small mass. They are often referred to as "ghost particles" because they rarely interact with other matter and are difficult to detect.
Neutrinos are studied and detected using specialized detectors, such as giant underground tanks of water or large underground detectors filled with liquid argon. When a neutrino collides with an atom in the detector, it produces a small flash of light that can be detected.
The current understanding is that neutrinos have a very small mass, but the exact value is still unknown. Scientists are actively working to measure the mass of neutrinos and better understand their properties.
Neutrinos are much smaller and have a different charge than electrons and protons. They also have a different type of spin called "spin half," which means that they have a spin of either +1/2 or -1/2.
Neutrinos are important because they can provide valuable information about the universe, such as the formation of stars and the composition of matter. They can also help scientists understand fundamental physics principles, such as the nature of mass and the behavior of particles at the smallest scales.