3 Questions: Investigating a long-standing neutrino thriller | MIT Information

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

In 2007, researchers developed the concept for a follow-up experiment, MicroBooNE, which just lately completed accumulating knowledge at Fermilab. MicroBooNE is a perfect take a look at of the MiniBooNE extra because of its use of a novel detector expertise referred to as the liquid argon time projection chamber (LArTPC), which yields high-resolution footage of the particles that get created in neutrino interactions.  

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. On 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 many large open questions in neutrino physics considerations the potential existence of a hypothetical particle referred to as the “sterile neutrino.” Discovering a brand new particle could be a really large deal as a result of it may give us clues to the bigger concept that explains the various particles we see. The commonest rationalization of the MiniBooNE extra includes the addition of such a sterile neutrino to the Commonplace Mannequin. Because of the results of neutrino oscillations, this sterile neutrino would present itself as an enhancement of electron neutrinos in MiniBooNE.

There are a lot of further anomalies seen in neutrino physics that point out this particle would possibly exist. Nonetheless, it’s tough to elucidate these anomalies together with MiniBooNE via a single sterile neutrino — the complete image doesn’t fairly match. Our group at MIT is taken with new physics fashions that may probably clarify this full image.

Q: What’s our present understanding of the MiniBooNE extra?

A: Our understanding has progressed considerably of late because of 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 % electron signature. We developed a “blended mannequin” 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 Bodily Evaluate D.

On the experimental finish, more moderen MicroBooNE outcomes — together with a deep-learning-based evaluation wherein our MIT group performed an necessary function — noticed no extra of neutrinos that produce electrons within the MicroBooNE detector. Conserving in thoughts the extent at which MicroBooNE could make the measurement, this means that the MiniBooNE extra can’t be attributed fully to further neutrino interactions. If it isn’t electrons, then it have to be photons, as a result of that’s the solely particle that may produce an identical signature in MiniBooNE. However we’re positive it isn’t photons produced by interactions that we learn about as a result of these are restricted to a low degree. So, they have to be coming from one thing new, such because the unique neutrino decay within the blended mannequin. Subsequent, MicroBooNE is engaged on a search that would isolate and establish these further photons. Keep 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. Equally, 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. Nonetheless, as a result of nuance of the variations, each duties turn into tough for standard algorithms.

MIT is a nexus of deep-learning concepts. Not too long ago, for instance, it grew to become the positioning of the Nationwide Science Basis AI Institute for Synthetic Intelligence and Elementary Interactions. It made sense for our group to construct on the intensive native experience within the area. We’ve got additionally had the chance to work with improbable teams at SLAC, Tufts College, Columbia College, and IIT, every with a robust information base within the ties between deep studying and neutrino physics.

One of many key concepts in deep studying is that of a “impartial community,” which is an algorithm that makes selections (reminiscent of figuring out particles in a LArTPC) based mostly on earlier publicity to a collection of coaching knowledge. Our group produced the primary paper on particle identification utilizing deep studying in neutrino physics, proving it to be a strong method. It is a main purpose why the recently-released outcomes of MicroBooNE’s deep learning-based evaluation place robust 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 achieved within the AI-rich setting at MIT.