From Fermilab Today: “Special Result of the Week – Fingerprinting the neutrino”
Fermilab continues to be a great source of strength in the U.S. Basic Research Community.
Thursday, June 7, 2012
Laura Fields, Northwestern University
“Neutrino scientists are currently trying to answer some exciting questions. How much do neutrinos weigh and why are they so light? How much do neutrinos change from one kind to another (called mixing) and why are their transformations so different from quark mixing? Do neutrinos mix differently from anti-neutrinos? To answer these questions, neutrino physicists must study how neutrinos and anti-neutrinos mix over time, which means using neutrino interactions to measure their energies and the distances they travel.
This plot shows the likelihood of an anti-neutrino colliding with a proton to produce a muon and a neutron as a function of the square of the four-momentum (a property that is proportional to the energy) given to the neutron (Q2). The red lines show theoretical predictions that include (dashed) and exclude (solid) a model in which the anti-neutrino can collide with several particles in the nucleus rather than just one.
“…if future experiments see a difference between neutrino and anti-neutrino mixing, it will be hard to determine the reason. On one hand, it could be caused by the neutrino and anti-neutrino actually mixing differently. On the other, it could be a difference between their interactions in the detector, which by definition is made only of matter (no antimatter).
The MINERvA collaboration has recently measured one of the most important interactions for mixing measurements. In this interaction, an anti-neutrino meets a proton, producing a muon and a neutron. This interaction is special because the energy of the anti-neutrino can be estimated simply by measuring the muon energy and direction. However, this isn’t as straightforward as it seems, and that may hamper our ability to infer neutrino energy.”
See the full article here.