Neutrinos are interacting with nuclei. The Jefferson Lab is a part of the DOE.
Neutrinos may be the key to finally solving a mystery of the origins of our universe, and preparations for two billion-dollar experiments are underway to reveal the particles' secrets. Nuclear physicists have turned to the electron to help them better understand how they can better prepare for critical information. Their research, which was done at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility, shows that major updates to the models are needed for the experiments to achieve high-precision results.
Neutrinos are generated by stars throughout the universe. These shy particles are difficult to study because they rarely interact with matter.
There is a phenomenon of neutrinos changing from one type to another. "It's interesting to study this phenomenon, because it is not well understood, and I was a graduate student in Professor Larry Weinstein's research group," said the co-lead author of the study. She is a researcher at Florida International University.
One way to study neutrinos is to build huge, ultra-sensitive detectors. The dense materials in the detectors make them more likely to interact with neutrinos. The particles are recorded by the detectors. Physicists can use that data to find out more about the neutrinos.
"The way that physicists are doing that is by measuring all particles coming out of the interaction of neutrinos with nuclei and reconstructing the incoming neutrino energy to learn more about the neutrino, its oscillations, and to measure them very, very precisely," explained Adi Ashkenazi. The contact author of the study is Ashkenazi, a research scholar at the Massachusetts Institute of Technology. She is a lecturer at Tel Aviv University.
The interactions of neutrinos with the heavy nuclei of the detectors are very complicated. The models we use to describe the neutrino energy reconstruction methods are not very good.
Physicists can use the methods to model the interactions with a simulation called GENIE. Physicists use GENIE to reproduce certain aspects of interactions between neutrinos and nuclei. It's difficult to directly test GENIE to ensure it will produce accurate and high-precision results from the new data that will be provided by future neutrino experiments, since there is so little known about neutrinos.
Nuclear physicists know a lot more about the electron than the team did.
The similarities between electrons and neutrinos are exploited. "We are using electron studies to verify interaction models."
Neutrinos and electrons have a lot in common. Both of them are elementary particles that aren't affected by the strong force.
The team used an electron-scattering version of GENIE, dubbed e-GENIE, to test the same incoming energy reconstruction methods that the researchers will use. They used recent electron results instead of using neutrinos.
The beams of electrons have very precise energies, and have been studied for years. We know their energy. We can compare the incoming energy to what we know. We can test how well our methods work, which is something you can't do with neutrinos.
The data for the study came from the experiments conducted with the CLAS detector at Jefferson Lab. The nature of matter is being probed by CEBAF. The simplest case to be studied in a neutrino experiment is interactions that produced an electron and a protons. The materials used in the experiment are similar to these.
The group worked to make sure that the electron version of GENIE was as close to the neutrino version as possible.
Afroditi Papadopoulou is a graduate student in Hen's research group at MIT and she is one of the co-lead authors of the study. "If the model doesn't work for electrons, where we are talking about the most simplified case, it will never work for neutrinos."
The data from electron-nucleus interactions are the most important source of data for accurate modeling. A good model can account for this effect.
When GENIE was used to model these data events, it performed worse.
This can affect the results. Papadopoulou said that the simulations must be able to reproduce the data with their beam energies before they can be trusted.
The person agreed.
The result is that there are aspects of the energy reconstruction methods that need to be improved. It shows a way to achieve this in the future.
The next step in this research is to test specific target nuclei of interest to researchers. Specific results for comparison will help researchers fine- tune their models.
According to the study team, the aim is to achieve broad agreement between data and models, which will help ensure DUNE and Hyper-Kamiokande can achieve their expected high-precision results.
Nature has more information about Hen, electron-beam energy reconstruction. www.nature.com/articles/s41586-021-0
Nature journal information.
The stage for the neutrino experiments was set by the electrons.
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