July 5, 2022


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After 9 years of work, we have the first complete results of the great Sino-American neutrino study

After 9 years of work, we have the first complete results of the great Sino-American neutrino study

| Astronomy / Physics

During 9 years of operation, the Daya Bay reactor neutrino experiment instruments have recorded 5.5 million neutrinos. The international team working on the experiment has now announced the first results for the entire data set. And most important of them Theta’s most accurate measurements are 13 (θ13), a key parameter for us to understand neutrino oscillations.

Roy Calchmidt, Berkeley Lab Roy Calchmidt, Berkeley Lab

Neutrinos are subatomic particles that fill the entire universe and are extremely difficult to see. Billions of neutrinos pass through our bodies every second. A neutrino can pass a wall of lead a light year thick without hitting any atoms.

One of the properties of neutrinos is oscillation, that is, the change between three smells: aromatic, tau and electron scents. The Day Bay Reactor Neutrino Experiment was designed to study the parameters that determine the oscillation potential. Among these parameters are mixing angles. When Daya Bay was designed in 2007, one of the mixing angles, θ13, was unknown. That is why the experiment was built to determine this parameter with unprecedented accuracy.

Day Bay Reactor Neutrino Experiment is located in Guangdong, China. It consists of large cylindrical particle detectors immersed in water and located in three underground caves. Eight detectors are responsible for detecting signals from antineutrinos coming from nearby nuclear reactors.

Daya Bay is an international project and the first joint physical project between China and the United States of America. It is attended by many scientific institutions, headed by the Institute of High Energy Physics of the Chinese Academy of Sciences on the Chinese side, and Lawrence Berkeley National Laboratory and Brookhaven National Laboratory on the American side.

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In every underground cave, Daya Bay detects the electron antineutrinos. Two of the caves are located near nuclear reactors, and the third is very far away, giving neutrinos time to oscillate. Scientists, by comparing the number of electronic antineutrinos that reached the detectors near and far from the reactors, could calculate how much the smell had changed from them, and from this they derived the value of theta 13.

In 2012, Daya Bay scientists announced the results of the first widely accepted measurements of theta13. Since then, they have constantly improved their measurements. In December 2020, after 9 years of experimental work, data collection was completed and analysis began. It turns out that Daya Bay far exceeded expectations. The value of 13 could have been measured with 2.5 times greater accuracy than assumed in the project assumptions. No experiment currently underway and planned should achieve such high accuracy.

Several teams of analysts have done Benedictine work by carefully analyzing the entire data set, taking into account changes in sensor performance over these nine years of operation. We used this data not only to isolate antineutrinos from them, but also to improve our understanding of background noise. This allowed us to achieve remarkable accuracyExperiments spokesman John Kao of the Institute of High Energy Physics says.

Thanks to accurate measurements of θ13, scientists will be able to study other parameters of neutrinos more easily and create more accurate models of subatomic particles and their interactions.

A better understanding of the properties and effects of antineutrinos could shed much light on the issue of matter-antimatter imbalances. It is now believed that the Big Bang produced the same amount of matter and antimatter. However, if that happened, it would have to be completely wiped out, leaving only the light. So there must be something that made the modern universe composed of matter. Perhaps this is the difference between neutrinos and antineutrinos. We have never detected any differences between particles and antiparticles in the leptons to which the neutrino belongs. We only find the differences between quarks and antiquarks. However, these differences are not enough to explain why matter has this feature in the universe. The answer may be hidden in neutrinosAnother spokesperson for the experiment, Cam Pyo Luke of Berkeley, says.

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Next-generation experiments such as DUNE (Deep Underground Neutrino Experiment) will be able to use measurements made by Daya Bay to accurately compare the properties of neutrinos and antineutrinos. DUNE will be the world’s most accurate neutrino detector. It will use the world’s most powerful neutrino source, PIP-II, under construction, in which Poland has invested.

Daya Bay Neutrino Reactor Theta 13 . Neutrino Experiment