Physicists announce the world’s most accurate measure of the lifetime of a neutron

Physicists announce the world’s most accurate measure of the lifetime of a neutron

An international team of physicists led by researchers at Indiana University Bloomington has released the world’s most accurate measure of neutron lifetime.

The team’s findings, which include scientists from more than 10 national laboratories and universities in the United States and abroad, show improvements twice as much as the previous measurements-with less than one-tenth of uncertainty.

The work is recorded in the journal Physical Review Letters of 13 October. This was the subject of live news at the 2021 Fall Meeting of the American Physical Society Division of Nuclear Physics. A pre-printed version of the paper is also available.

David Baxter, president of the department at IU Bloomington College of Arts and Sciences, said, “This work sets a new gold-standard for measurement that is of fundamental importance to questions such as the relative abundance of elements created in the early universe.” Physics. “We are proud of IU’s long-term role as a leading institution in this work.”

At the time of the study, IU-affiliated authors Nathan Callahan, Maria David and Francisco Gonzalez were graduate students; Engineer Walt Fox; Rudy Chen-Yu Liu, professor of physics; Research scientist Daniel Salvat; And mechanical technician John Vanderwarp. (Callahan and Gonzalez are currently affiliated with the Argonne National Laboratory and the Oak Ridge National Laboratory, respectively.) The research was conducted at the Los Alamos National Laboratory.

The scientific purpose of the experiment is to measure how long the average free neutron lives outside the confines of an atomic nucleus.

Salvat, who led the experiments at Los Alamos, said: “The process by which neutrons are ‘depleted’ into protons – with the emission of light electrons and neutrinos with almost no mass – is one of the most fascinating processes known to physicists.” “Attempting to measure this value precisely is significant because understanding the exact life of neutrons can shed light on how the universe evolved – as well as allowing physicists to find flaws in our existing subatomic universe model but no one has yet been able to detect.”

The neutrons used in the study are produced by the Los Alamos Neutron Science Center ultracold neutron source at the Los Alamos National Lab. The UCNtau experiment captured these neutrons, whose temperature has been brought to almost absolute zero, in a “bathtub” with about 4,000 magnets. After waiting 30 to 90 minutes, the researchers count the living neutrons in the tub as they are magnified against the force of gravity.

The unique design of the UCNtau trap allows neutrons to be stored for more than 11 days, significantly longer than previous designs, reducing the need for systematic improvements that can reduce the effects of lifetime measurements. In two years, the researchers in the study obtained approximately 40 million neutrons using this calculated method. These efforts were the dissertation work of Gonzalez, who collected data at Los Alamos as an IU graduate student from 2017 to 2019 and led the analysis of the published results.

Salvat said the results of the experiment would help physicists confirm or deny the validity of the “cabibo-kobayashi-muskava matrix”, which includes subatomic particles called quarks and plays an important role in the widely accepted “standard model” of particle physics. This will help physicists understand the potential role that new ideas in physics, such as neutrons decomposing into dark matter, can help develop theories about the universe, as well as explain how the first atomic nuclei formed.

“The underlying model explaining neutron decay involves changing their identification by quarks, but recently revised calculations suggest that this process may not be as previously predicted,” Salwat said. “Our new measurement of the lifespan of neutrons will provide an independent assessment to solve this problem, or provide much-discovered evidence for the discovery of new physics.”

Sneha Mali

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