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


Neutrinos interacting with nuclei. Credit score: DOE’s Jefferson Lab

Early-career nuclear physicists present that a greater understanding of how neutrinos work together with matter is required to make the most of upcoming experiments.

Neutrinos could also be the key to lastly fixing a thriller of the origins of our matter-dominated universe, and preparations for two main, billion-dollar experiments are underway to disclose the particles’ secrets and techniques. Now, a staff of nuclear physicists have turned to the humble electron to supply perception for how these experiments can higher put together to seize important info. Their analysis, which was carried out at the U.S. Division of Power’s Thomas Jefferson Nationwide Accelerator Facility and lately revealed in Nature, reveals that main updates to neutrino fashions are wanted for the experiments to realize high-precision outcomes.

Neutrinos are ubiquitous, generated in copious numbers by stars all through our universe. Although prevalent, these shy particles hardly ever work together with matter, making them very tough to check.

“There may be this phenomenon of neutrinos altering from one kind to a different, and this phenomenon is known as neutrino oscillation. It’s attention-grabbing to check this phenomenon, as a result of it isn’t effectively understood,” mentioned Mariana Khachatryan, a co-lead creator on the examine who was a graduate scholar at Outdated Dominion College in Professor and Eminent Scholar Larry Weinstein’s analysis group when she contributed to the analysis. She is now a postdoctoral analysis affiliate at Florida Worldwide College.

One technique to examine neutrino oscillation is to construct gigantic, ultra-sensitive detectors to measure neutrinos deep underground. The detectors sometimes include dense supplies with giant nuclei, so neutrinos usually tend to work together with them. Such interactions set off a cascade of different particles which might be recorded by the detectors. Physicists can use that knowledge to tease out details about the neutrinos.

“The way in which that neutrino physicists are doing that’s by measuring all particles popping out of the interplay of neutrinos with nuclei and reconstructing the incoming neutrino vitality to study extra about the neutrino, its oscillations, and to measure them very, very exactly,” defined Adi Ashkenazi. Ashkenazi is the examine’s contact creator who labored on this venture as a analysis scholar in Professor Or Hen’s analysis group at the Massachusetts Institute of Expertise. She is now a senior lecturer at Tel Aviv College.

“The detectors are made of heavy nuclei, and the interactions of neutrinos with these nuclei are literally very sophisticated interactions,” Ashkenazi mentioned. “These neutrino vitality reconstruction strategies are nonetheless very difficult, and it’s our work to enhance the fashions we use to explain them.”

These strategies embrace modeling the interactions with a theoretical simulation known as GENIE, permitting physicists to deduce the energies of the incoming neutrinos. GENIE is an amalgam of many fashions that every assist physicists reproduce sure features of interactions between neutrinos and nuclei. Since so little is understood about neutrinos, it’s tough to straight check GENIE to make sure it would produce each correct and high-precision outcomes from the new knowledge that will likely be supplied by future neutrino experiments, comparable to the Deep Underground Neutrino Experiment (DUNE) or Hyper-Kamiokande.

To check GENIE, the staff turned to a humble particle that nuclear physicists know much more about: the electron.

“This exploits the similarities between electrons and neutrinos. We’re utilizing electron research to validate neutrino-nucleus interplay fashions,” mentioned Khachatryan.

Neutrinos and electrons have many issues in frequent. They each belong to the subatomic particle household known as leptons, so they’re each elementary particles that aren’t affected by the robust pressure.

On this examine, the staff used an electron-scattering model of GENIE, dubbed e-GENIE, to check the similar incoming vitality reconstruction algorithms that neutrino researchers will use. As an alternative of utilizing neutrinos, they used latest electron outcomes.

“Electrons have been studied for years, and the beams of the electrons have very exact energies,” mentioned Ashkenazi. “We all know their energies. And after we try to reconstruct that incoming vitality, we will examine that to what we all know. We will check how effectively our strategies work for numerous energies, which is one thing you’ll be able to’t do with neutrinos.”

The enter knowledge for the examine got here from experiments carried out with the CLAS detector at Jefferson Lab’s Steady Electron Beam Accelerator Facility, a DOE consumer facility. CEBAF is the world’s most superior electron accelerator for probing the nature of matter. The staff used knowledge that straight mirrored the easiest 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 are just like supplies utilized in neutrino experiment detectors.

Additional, the group labored to make sure that the electron model of GENIE was as parallel as doable to the neutrino model.

“We used the very same simulation as utilized by neutrino experiments, and we used the similar corrections,” defined Afroditi Papadopoulou, co-lead creator on the examine and a graduate scholar at MIT who can be in Hen’s analysis group. “If the mannequin doesn’t work for electrons, the place we’re speaking about the most simplified case, it would by no means work for neutrinos.”

Even on this easiest case, correct modeling is essential, as a result of uncooked knowledge from electron-nucleus interactions sometimes reconstruct to the right incoming electron beam vitality lower than half the time. A great mannequin can account for this impact and proper the knowledge.

Nevertheless, when GENIE was used to mannequin these knowledge occasions, it carried out even worse.

“This could bias the neutrino oscillation outcomes. Our simulations should be capable of reproduce our electron knowledge with its recognized beam energies earlier than we will belief they are going to be correct in neutrino experiments,” mentioned Papadopoulou.

Khachatryan agreed.

“The end result is definitely to level out that there are features of these vitality reconstruction strategies and fashions that must be improved,” mentioned Khachatryan. “It additionally reveals a pathway to realize this for future experiments.”

The subsequent step for this analysis is to check particular goal nuclei of curiosity to neutrino researchers and at a broader spectrum of incoming electron energies. Having these particular outcomes for direct comparability will help neutrino researchers in fine-tuning their fashions.

In accordance with the examine staff, the intention is to realize broad settlement between knowledge and fashions, which is able to assist guarantee DUNE and Hyper-Kamiokande can obtain their anticipated high-precision outcomes.

Reference: “Electron Beam Power Reconstruction for Neutrino Oscillation Measurements” 24 November 2021, Nature.
DOI: 10.1038/s41586-021-04046-5





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

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