Electrons Set the Stage for Neutrino Experiments– Solving Mystery of the Origins of Our Matter-Dominated Universe

Neutrinos Interacting With Nuclei

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Neutrinos engaging with nuclei. Credit: DOE’s Jefferson Lab

Early- profession nuclear physicists reveal that a much better understanding of how neutrinos connect with matter is required to maximize upcoming experiments.

Neutrinos might be the secret to lastly resolving a secret of the origins of our matter-dominated universe, and preparations for 2 significant, billion-dollar experiments are underway to expose the particles’ tricks. Now, a group of nuclear physicists have actually relied on the modest electron to offer insight for how these experiments can much better prepare to record important details. Their research study, which was performed at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility and just recently released in Nature, exposes that significant updates to neutrino designs are required for the experiments to accomplish high-precision outcomes.

Neutrinos are common, created in generous numbers by stars throughout our universe. Though common, these shy particles seldom connect with matter, making them extremely tough to study.

“There is this phenomenon of neutrinos changing from one type to another, and this phenomenon is called neutrino oscillation. It’s interesting to study this phenomenon, because it is not well understood,” stated Mariana Khachatryan, a co-lead author on the research study who was a college student at Old Dominion University in Professor and Eminent Scholar Larry Weinstein’s research study group when she added to the research study. She is now a postdoctoral research study partner at Florida International University.

One method to study neutrino oscillation is to construct enormous, ultra-sensitive detectors to determine neutrinos deep underground. The detectors usually consist of thick products with big nuclei, so neutrinos are most likely to connect with them. Such interactions activate a waterfall of other particles that are taped by the detectors. Physicists can utilize that information to tease out details about the neutrinos.

“The way that neutrino 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,” described AdiAshkenazi Ashkenazi is the research study’s contact author who dealt with this job as a research study scholar in Professor Or Hen’s research study group at the Massachusetts Institute ofTechnology She is now a senior speaker at Tel Aviv University.

“The detectors are made of heavy nuclei, and the interactions of neutrinos with these nuclei are actually very complicated interactions,” Ashkenazi stated. “Those neutrino energy reconstruction methods are still very challenging, and it is our work to improve the models we use to describe them.”

These approaches consist of modeling the interactions with a theoretical simulation called GENIE, permitting physicists to presume the energies of the inbound neutrinos. GENIE is an amalgam of lots of designs that each assistance physicists replicate particular elements of interactions in between neutrinos and nuclei. Since so little is understood about neutrinos, it’s tough to straight evaluate GENIE to guarantee it will produce both precise and high-precision arise from the brand-new information that will be offered by future neutrino experiments, such as the Deep Underground Neutrino Experiment (DUNE) or Hyper-Kamiokande

To test GENIE, the group relied on a simple particle that nuclear physicists understand a lot more about: the electron.

“This exploits the similarities between electrons and neutrinos. We are using electron studies to validate neutrino-nucleus interaction models,” stated Khachatryan.

Neutrinos and electrons have lots of things in typical. They both come from the subatomic particle household called leptons, so they are both primary particles that aren’t impacted by the strong force.

In this research study, the group utilized an electron-scattering variation of GENIE, called e-GENIE, to evaluate the very same inbound energy restoration algorithms that neutrino scientists will utilize. Instead of utilizing neutrinos, they utilized current electron outcomes.

“Electrons have been studied for years, and the beams of the electrons have very precise energies,” statedAshkenazi “We know their energies. And when we are trying to reconstruct that incoming energy, we can compare that to what we know. We can test how well our methods work for various energies, which is something you can’t do with neutrinos.”

The input information for the research study originated from experiments performed with the CLAS detector at Jefferson Lab’s Continuous Electron Beam Accelerator Facility, a DOE user center. CEBAF is the world’s most sophisticated electron accelerator for penetrating the nature of matter. The group utilized information that straight mirrored the most basic case to be studied in neutrino experiments: interactions that produced an electron and a proton (vs. a muon and a proton) from nuclei of helium, carbon and iron. These nuclei resemble products utilized in neutrino experiment detectors.

Further, the group worked to make sure that the electron variation of GENIE was as parallel as possible to the neutrino variation.

“We used the exact same simulation as used by neutrino experiments, and we used the same corrections,” described Afroditi Papadopoulou, co-lead author on the research study and a college student at MIT who is likewise in Hen’s research study group. “If the model doesn’t work for electrons, where we are talking about the most simplified case, it will never work for neutrinos.”

Even in this most basic case, precise modeling is important, due to the fact that raw information from electron-nucleus interactions usually rebuild to the appropriate inbound electron beam energy less than half the time. An excellent design can represent this impact and fix the information.

However, when GENIE was utilized to design these information occasions, it carried out even worse.

“This can bias the neutrino oscillation results. Our simulations must be able to reproduce our electron data with its known beam energies before we can trust they will be accurate in neutrino experiments,” stated Papadopoulou.

Khachatryan concurred.

“The result is actually to point out that there are aspects of these energy reconstruction methods and models that need to be improved,” statedKhachatryan “It also shows a pathway to achieve this for future experiments.”

The next action for this research study is to evaluate particular target nuclei of interest to neutrino scientists and at a more comprehensive spectrum of inbound electron energies. Having these particular outcomes for direct contrast will help neutrino scientists in fine-tuning their designs.

According to the research study group, the goal is to accomplish broad arrangement in between information and designs, which will assist make sure DUNE and Hyper-Kamiokande can accomplish their anticipated high-precision outcomes.

Reference: “Electron Beam Energy Reconstruction for Neutrino Oscillation Measurements” by M. Khachatryan, A. Papadopoulou, A. Ashkenazi, F. Hauenstein, A. Nambrath, A. Hrnjic, L. B. Weinstein, O. Hen, E. Piasetzky, M. Betancourt, S. Dytman, K. Mahn, P. Coloma, the CLAS Collaboration and e4ν Collaboration, 24 November 2021, Nature
DOI: 10.1038/ s41586-021-04046 -5

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