It can be hard to detect the ghostly neutrino, which rarely interacts with matter. To overcome this, neutrino experiments use detectors made of neutrons and protons bound up in heavy nuclei. The way these nuclei affect the particles made by neutrino interactions is not well understood, so MINERvA is working to measure this in as many ways as possible.
Sometimes a neutrino creates a quark-antiquark pair called a pion, and the neutrino itself can change into a charged particle called a muon (an antineutrino can create an antimuon). The pions often interact with the nucleus where they were made, changing their charge or even stopping before they can leave. On the other hand, the muons or antimuons are not affected by the nucleus at all, according to predictions. So one way to measure the effects of the nucleus is to take the same interaction and look at it from both sides: from the pion side and from the muon side.
MINERvA presented results about the pion side neutrino measurements and the antineutrino measurements. At today’s Joint Experimental-Theoretical Physics Seminar, the MINERvA collaboration will show new information about the muons that are made along with the pions in these interactions and provide a more complete picture of the interaction.
There are models that try to describe this process. Neutrino experiments, especially those that try to measure how neutrinos change over time, need those models to get both the muon side and the pion side right: It’s not enough to describe only one kind of particle. Creating these models has been a challenge due to the complicated nature of the nucleus. In addition, there are disagreements between these models and the experimental data taken by many neutrino experiments. To make matters even more confusing, sometimes different measurements of this process at different energies (or on different nuclei) don’t all agree with the same model.
By studying the muons as well as the energies of the pions, we can compare between the different models of the nucleus and their effects on the interaction. Eventually there will be at least one model that can describe all the data. This will give us a better picture of the nucleus, which ultimately improves our ability to measure the neutrino.