Thu. Jan 20th, 2022

October surprise?  Researchers find no hint of sterile neutrino in the international MicroBooNE experiment

In this 2013 photo, workers are installing a component of MicroBooNE’s precision detector, called a time projection chamber, into the cylindrical container or cryostat. Credit: Reidar Hahn, Fermilab.

New results from the MicroBooNE experiment at the US Department of Energy’s Fermi National Accelerator Laboratory strike at a theoretical particle known as the sterile neutrino. There is no such thing.

For more than two decades, this theory of a fourth neutrino has been a promising explanation for anomalies seen in previous physics experiments. Finding a new particle would be a great discovery and a radical shift in our understanding of the universe. And also a likely Nobel Prize. But it does not have to be.

Among the scientists who are part of the international, multi-university multi-agency MicroBooNE effort is Camillo Mariani, a professor of the Department of Physics, part of the Virginia Tech College of Science. He worked on the project from its inception, beginning in 2012.

“The latest results are very important to the neutrino community, for two main aspects. These are the first major physics results coming out of a liquid argon time projection chamber (TPC). Liquid argon TPC has always been very promising in terms of technology. But never produced great physics results.The second, of course, is that we now understand nature better, “said Mariani, who is also a member of the Center for Neutrino Physics at Virginia Tech and director of the Kimballton Underground Research Facility in Giles County.

Researchers find no indication of sterile neutrino

The international MicroBooNE experiment uses a 170-ton detector placed in Fermilab’s neutrino beam. The experiment studies neutrino interactions and has not found any indication of a theorized fourth neutrino called the sterile neutrino. Credit: Reidar Hahn, Fermilab.

The results, released today, are in line with the Standard Model of Particle Physics, scientists’ best theory of how the universe works. The data are in line with what the standard model predicts: three kinds of neutrino – neither more nor less. Neutrinos come in three known types – electron, muon and tau neutrinos – and can switch between these flavors in a certain way when they travel.

“For many years we have been investigating the possibility of the existence of a fourth neutrino, a new particle that was not predicted in the standard model of particle physics,” Mariani added. “The MiniBooNE experiment in early 2010 showed an anomaly that could possibly be explained by the existence of a sterile neutrino. I was part of this collaboration and author of one of the latest articles from MiniBooNE. for technology and detailed offerings from liquid argon projection chambers, MicroBooNE was able to disfavor the interpretation of the MiniBooNE low energy surplus as due to sterile neutrino.It’s a little sad to see the possibility of detecting another particle, but we advance our knowledge of nature, and that is a very important thing. “

MicroBooNE is a 170-ton neutrino detector that is roughly the size of a school bus that has been powered by the Fermi National Accelerator Laboratory near Chicago since 2015. The international experiment has close to 200 collaborators from 36 institutions in five countries. They used the technology to capture spectacularly accurate 3D images of neutrino events and investigate particle interactions in detail – a much-needed probe in the subatomic world, according to FermiLab.

The MicroBooNE detector uses special light sensors and more than 8,000 carefully attached wires to capture particle traces. It is housed in a 40-foot cylindrical container filled with 170 tons of pure liquid argon. Neutrinos collide into the dense, transparent liquid and release additional particles that the electronics can absorb. The resulting images show detailed particle paths and, crucially, distinguish electrons from photons.

Researchers find no indication of sterile neutrino

MicroBooNE’s advanced liquid argon technology enables researchers to capture detailed images of particle traces. This electron neutrino event shows an electron shower and a proton trace. Credit: MicroBooNE collaboration.

From 2012 with his arrival in Blacksburg, Mariani and several postdoc researchers participated in the design, installation and commissioning of the MicroBooNE detector.

“We were in charge of the online system that monitors the quality of the data coming out of the detector, and we did some initial detector work with students who built a mini detector and drove it to Fermilab in 2014. The detector was used to identify muons. crosses the main detector volume, “said Mariani.

Neutrinos are one of the basic particles in nature. They are neutral, incredibly small and the most widespread particle with mass in our universe – although they rarely interact with other matter. They are also particularly exciting for physicists with a series of unanswered questions. These riddles include why their masses are so vanishingly small and whether they are responsible for the dominance of matter over antibody in our universe. This makes neutrinos a unique window to explore how the universe works on the smallest scales, Fermilab said in a press release.

With sterile neutrinos further disfavored as the explanation for anomalies spotted in neutrino data, researchers are investigating other possibilities, according to Fermilab. These include things as exciting as light created by other processes during neutrino collisions or as exotic as the theorized dark matter.

Researchers find no indication of sterile neutrino

Workers install a component of the MicroBooNE precision detector (called a time projection chamber) in the cylindrical container or cryostat. Credit: Reidar Hahn, Fermilab.

Mark Pitt, department chair and professor of physics, said many of his faculty from the Center for Neutrino Physics have been actively involved in the search for the sterile neutrino.

“Detection technologies for searching for sterile neutrinos have been an active interest of Center Faculty members Jonathan Link and Bruce Vogelaar,” Pitt said. “On the theoretical side, Center Director Patrick Huber and Camillo’s group have been at the forefront of understanding how liquid argon experiments like MicroBooNE are affected by the modeling of neutrinos that interact with the argon nucleus.”

Pitt added that as far back as 2011, Mariani hosted the international workshop Sterile Neutrinos at the Crossroads as one of the center’s first events.

Huber, director of the center, added: “This is the first time we got a real kind of top-of-the-line physics observation from a liquid argon detector, it also shows that this is a complicated technology. The analysis took a long time. They had stopped taking data a while ago, but just converting this raw data from the detector to a statement on physics is a really difficult process.… It’s a good day for science, we learned something, we learned to it’s photons, not electrons. “

What’s next for Mariani? He is part of the new Deep Underground Neutrino Experiment (or DUNE for short), an international flagship experiment that also hosts Fermilab, which already has more than 1,000 researchers from over 30 countries. DUNE will study oscillations by sending neutrinos 800 miles through the ground to detectors at the mile-deep Sanford Underground Research Facility. The combination of short- and long-range neutrino experiments will give scientists insight into how these fundamental particles work. Now under construction, the detector is expected to go live in 2027.

Scientists assemble final detector of Fermilab’s Short-Baseline Neutrino Program

More information:
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Provided by Virginia Tech

Citation: Researchers find no hint of sterile neutrino (2021, October 27) retrieved October 27, 2021 from

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