Aug 9, 2015 05:28 PM
Two neutrino events recently.
First, Fermilab has been firing neutrinos through solid rock towards a detector in Minnesota. They make the neutrinos by firing protons at a target. That results in all kinds of subatomic debris, including pions (quarks + antiquarks) that can be focused into a beam. Then some of the pions decay, producing neutrinos that remain in the beam.
Apparently for technical reasons these should be muon neutrinos, called that because they produce muons (heavier relatives of the electron) when they collide with something. But physicists have been observing fewer muon neutrinos than predicted and more electron neutrinos. They interpret this as evidence of neutrinos switching back and forth between the muon and electon neutrino forms, something that's been observed before. This is reportedly rather mysterious and this new setup hopefully will allow them to study it. One implication concerns mass. It was originally believed that neutrinos have no mass, but it seems that they can acquire it through this switching process. So one hypothesis as to what the missing 'dark matter' mass is, is at least in part neutrinos with mass.
The other bit of neutrino news concerns a detector in Antarctica. It's detected the most energetic neutrino ever observed, a muon neutrino of astronomical origin. One feature of this detector is that it can determine the direction the neutrino came from. Since neutrinos rarely interact with conventional matter and don't respond to most of the physical forces, they presumably traveled here in a straight line from their points of origin. So there's hope this can be used as kind of a neutrino telescope giving astrophysicists information about high-energy events in space.
http://www.theguardian.com/science/life-...est-energy
First, Fermilab has been firing neutrinos through solid rock towards a detector in Minnesota. They make the neutrinos by firing protons at a target. That results in all kinds of subatomic debris, including pions (quarks + antiquarks) that can be focused into a beam. Then some of the pions decay, producing neutrinos that remain in the beam.
Apparently for technical reasons these should be muon neutrinos, called that because they produce muons (heavier relatives of the electron) when they collide with something. But physicists have been observing fewer muon neutrinos than predicted and more electron neutrinos. They interpret this as evidence of neutrinos switching back and forth between the muon and electon neutrino forms, something that's been observed before. This is reportedly rather mysterious and this new setup hopefully will allow them to study it. One implication concerns mass. It was originally believed that neutrinos have no mass, but it seems that they can acquire it through this switching process. So one hypothesis as to what the missing 'dark matter' mass is, is at least in part neutrinos with mass.
The other bit of neutrino news concerns a detector in Antarctica. It's detected the most energetic neutrino ever observed, a muon neutrino of astronomical origin. One feature of this detector is that it can determine the direction the neutrino came from. Since neutrinos rarely interact with conventional matter and don't respond to most of the physical forces, they presumably traveled here in a straight line from their points of origin. So there's hope this can be used as kind of a neutrino telescope giving astrophysicists information about high-energy events in space.
http://www.theguardian.com/science/life-...est-energy