The search for neutrino's mass.

[blike]

CNN has an interesting article about how scientists are testing to see if neutrinos have mass. The experiment will cost 170 million dollars.

 

 

The article states: The beam will be fired from a particle accelerator near Chicago toward Soudan where it will pass through magnetized sheets of metal.

 

Because of their elusive nature, most of the neutrinos in the beam will pass right through the solid rock between the two places. Most will pass through Soudan's metal plates as well, but a few will collide with atoms in the sheets and computers will record and document the interaction.

 

In other words, "We're going to take a sawed-off shotgun and blast a bunch of neutrinos toward Minnesota and measure what sticks," said Marvin Marshak, a physics professor at the University of Minnesota.

 

If the neutrinos remain unchanged, they have no mass. But if they do have mass, they'll be altered on the voyage from Chicago to Minnesota by a process that can only act on particles that respond to gravity.

 

[fafalone]

They already proved neutrinos have mass. There are 3 flavors of neutrinos, e- neutrinos, muon neutrinos, and tau neutrinos. A observed propert called neutrino oscillation involves neutrinos changing flavor in a vacuum. In order for this to happen, it must have mass. Another proof came from measurement of the decay of a tritium nucleus (2).

Furthermore, Klapdor-Kleingrothaus et al. (1) recently demonstrated that the lepton number is not conserved in the neutrinoless double-b-decay reaction 76Ge->76Se + 2e1 (76 is superscript), which violates lepton conservation by 2 units.

Not only does this show they have mass, but that all 3 flavors have almost the same mass. Their measurements say the mass of any kind of neutrino is ~2x10^-9 GeV c1 2.

 

(1) Klapdor-Kleingrothaus, H. V., Dietz, A., Harney, H. L. & Krivosheina, I. V. Mod. Phys. Lett. A 16, 2409–2420 (2001)

 

(2) Bonn, J. et al. (MAINZ collaboration) Nucl. Phys. Proc. Suppl. 91, 273–279 (2001).

 

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ps- blike, if you read the nature articles you sent me, you would have already known of these experiments