Investigating a long-standing neutrino thriller


This roughly 70-centimeter-wide picture depicts a MicroBooNE electron neutrino occasion, with an electron bathe (straight line and dots backside left to high proper) and a proton monitor (quick pink line at backside left). MIT researchers have been utilizing the MicroBooNE experiment at Fermilab to uncover new secrets and techniques behind neutrinos. Credit: MicroBooNE Collaboration.

Neutrinos are one of the vital mysterious members of the Standard Model, a framework for describing basic forces and particles in nature. While they’re among the many most considerable identified particles within the universe, they work together very hardly ever with matter, making their detection a difficult experimental feat. One of the long-standing puzzles in neutrino physics comes from the Mini Booster Neutrino Experiment (MiniBooNE), which ran from 2002 to 2017 on the Fermi National Accelerator Laboratory, or Fermilab, in Illinois. MiniBooNE noticed considerably extra neutrino interactions that produce electrons than one would anticipate given our greatest data of the Standard Model—and physicists are attempting to know why.

In 2007, researchers developed the concept for a follow-up experiment, MicroBooNE, which not too long ago completed accumulating knowledge at Fermilab. MicroBooNE is a perfect take a look at of the MiniBooNE extra due to its use of a novel detector know-how referred to as the liquid argon time projection chamber (LArTPC), which yields high-resolution photos of the particles that get created in neutrino interactions.

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Physics graduate college students Nicholas Kamp and Lauren Yates, together with Professor Janet Conrad, all inside the MIT Laboratory for Nuclear Science, have performed a number one function in MicroBooNE’s deep-learning-based seek for an extra of neutrinos within the Fermilab Booster Neutrino Beam. In this interview, Kamp discusses the way forward for the MiniBooNE anomaly inside the context of MicroBooNE’s newest findings.

Q: Why is the MiniBooNE anomaly a giant deal?

A: One of the large open questions in neutrino physics considerations the doable existence of a hypothetical particle known as the “sterile neutrino.” Finding a new particle could be a really massive deal as a result of it can provide us clues to the bigger idea that explains the numerous particles we see. The commonest rationalization of the MiniBooNE extra includes the addition of such a sterile neutrino to the Standard Model. Due to the results of neutrino oscillations, this sterile neutrino would present itself as an enhancement of electron neutrinos in MiniBooNE.

There are many extra anomalies seen in neutrino physics that point out this particle would possibly exist. However, it’s troublesome to clarify these anomalies together with MiniBooNE by means of a single sterile neutrino—the total image does not fairly match. Our group at MIT is involved in new physics fashions that may probably clarify this full image.

Q: What is our present understanding of the MiniBooNE extra?

A: Our understanding has progressed considerably of late due to developments in each the experimental and theoretical realms.

Our group has labored with physicists from Harvard, Columbia, and Cambridge universities to discover new sources of photons that may seem in a theoretical mannequin that additionally has a 20 p.c electron signature. We developed a “mixed model” that includes two sorts of unique neutrinos—one which morphs to electron taste and one which decays to a photon. This work is forthcoming in Physical Review D.

On the experimental finish, newer MicroBooNE outcomes—together with a deep-learning-based evaluation during which our MIT group performed an vital function—noticed no extra of neutrinos that produce electrons within the MicroBooNE detector. Keeping in thoughts the extent at which MicroBooNE could make the measurement, this implies that the MiniBooNE extra can’t be attributed fully to further neutrino interactions. If it is not electrons, then it should be photons, as a result of that’s the solely particle that may produce an identical signature in MiniBooNE. But we’re certain it’s not photons produced by interactions that we learn about as a result of these are restricted to a low degree. So, they should be coming from one thing new, such because the unique neutrino decay within the blended mannequin. Next, MicroBooNE is engaged on a search that might isolate and establish these extra photons. Stay tuned!

Q: You talked about that your group is concerned in deep-learning-based MicroBooNE evaluation. Why use deep studying in neutrino physics?

A: When people have a look at photos of cats, they will inform the distinction between species with out a lot problem. Similarly, when physicists have a look at photos coming from a LArTPC, they will inform the distinction between the particles produced in neutrino interactions with out a lot problem. However, as a result of nuance of the variations, each duties transform troublesome for typical algorithms.

MIT is a nexus of deep-learning concepts. Recently, for instance, it turned the location of the National Science Foundation AI Institute for Artificial Intelligence and Fundamental Interactions. It made sense for our group to construct on the in depth native experience within the discipline. We have additionally had the chance to work with improbable teams at SLAC, Tufts University, Columbia University, and IIT, every with a powerful data base within the ties between deep studying and neutrino physics.

One of the important thing concepts in deep studying is that of a “neutral network,” which is an algorithm that makes choices (equivalent to figuring out particles in a LArTPC) based mostly on earlier publicity to a set of coaching knowledge. Our group produced the primary paper on particle identification utilizing deep studying in neutrino physics, proving it to be a robust approach. This is a significant cause why the recently-released outcomes of MicroBooNE’s deep learning-based evaluation place sturdy constraints on an electron neutrino interpretation of the MiniBooNE extra.

All in all, it’s extremely lucky that a lot of the groundwork for this evaluation was executed within the AI-rich setting at MIT.

New results from MicroBooNE provide clues to particle physics mystery

More info:
S. Vergani et al, Explaining the MiniBooNE extra by means of a blended mannequin of neutrino oscillation and decay, Physical Review D. … ec5bd4195b8b262a3bf4

This story is republished courtesy of MIT News (, a preferred web site that covers information about MIT analysis, innovation and educating.

Investigating a long-standing neutrino thriller (2021, October 29)
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