Beaming Neutrinos Through Earth?

TheMatt writes: "An article at PhysicsWeb talks about a proposed project by scientists at FermiLab. The project would involve sending a beam of neutrinos 10,000 km through the earth to a detector at SuperKamiokande. The hope is that passing through so much matter would alter the beam enough to better study CP (charge-parity) violation."

Comments

Re:How do you aim a 'beam' of neutrinos?

[stevelinton]

You don't. You aim a beam of something else, protons, say (in the usual way with magnets) and then smash it into a carefully selected target. The collisions make lots of neutrinos (and other junk, but a few km or rock absorbs that) and they are travelling, pretty much, in the direction of the original beam.

Re:First impression

[mcelrath]

The article says construction would have to begin by 2006, so there'll definitely be enough time for me to get out of the way.

Neutrinos interact so weakly that standing in the beamline would not cause you any harm. I have walked through the beamline of the NuTeV Experiment (while it was running). Not only that but a beam pointed at Super-K will not be a straight line, it will be more of a cone. At the surface in Japan, where the beam exits the earth, the size of the beam will be ~kilometers.

-- Bob

Close, but no cigar

[Spamalamadingdong]

The collisions of protons with targets don't make neutrinos, they make pions. Charged pions can be directed magnetically; when they decay to muons, they create neutrinos and when the muons decay to electrons they create still more neutrinos. If the kinetic energy of the decay is small compared to the energy of the original beam, the neutrinos will be travelling in more or less the same direction as the parent particles.

Neutrinos going to Mass

[Spamalamadingdong]

Will different densities affect how the neutrinos travel (making aiming a difficulty)? Or is that pretty much what they're depending on?

I'm no particle physicist, but I believe that density, period (density times distance) is the objective of the long-baseline beam project. Neutrinos can travel through millions of miles of matter like light through glass; they are very hard to scatter because they interact so weakly. On the other hand, it appears that interactions which change the neutrino's flavor without scattering it are much more likely, which is why our early detectors only found 1/3 of the neutrinos we'd expect the Sun to emit from its rate of fusion. (When protons are converted to neutrons, charge and parity are conserved by the emission of a positron and a neutrino; a lot of these electron neutrinos apparently switch flavors to mu and tau neutrinos on their way out of the core.)

And if they miss? They won't be seeing any neutrinos coming from the source accelerator. If they aimed at you, you'd never notice any more than you notice the millions of solar neutrinos streaking through your body every second like ghost bullets from an etherial machine gun. Hey, they don't even slime you...