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75 years ago, Rosemary Brown “discovered a strange phenomenon of particle decomposition.”
He helped transform our understanding of physics.
In 1948, she was a young doctoral student at the University of Bristol in England.
After marrying physicist Peter Fowler in 1949, she decided to give up her career and devote herself to her family.
She changed her maiden name and adopted her husband’s, with whom she had three children.
Decades later, someone brought him unexpected news.
This week, at the age of 98, his former university awarded him an honorary doctorate.
The institution’s president, Paul Nurse, praised its “intellectual rigor and curiosity,” adding that it “paved the way for important discoveries that continue to shape the work of physicists and our understanding of the universe.”
Fowler’s discovery of the kappa particle helped predict particles such as the Higgs boson.
Indeed, the confirmation of the existence of the Higgs boson at CERN in Switzerland in 2012 is one of the greatest achievements of modern physics.
The discovery of the K-Meson particle led to a revolution in particle physics theory.
After receiving the award at a private graduation ceremony near her home in Cambridge, the doctor said she felt “very honoured”, although she added: “I have not done anything since then that deserves special consideration.”
Nurse was awarded the 2001 Nobel Prize in Medicine along with Leland Hartwell and Tim Hunter, and was responsible for awarding him an honorary Doctor of Science degree.
Fowler was born in Suffolk in 1926 and grew up in Malta, Portsmouth and Bath as his family moved around for his father’s work as an engineer in the Royal Navy.
In school, Rosemary found that “math and science were easy, but writing papers was hard.”
In 1948, the Bristol Cosmic Ray Physics Group, led by Professor Cecil Powell, was searching for new elementary particles.
They had discovered the pion (a subatomic particle), for which Professor Powell won the 1950 Nobel Prize.
Fowler, then just 22, noticed something while observing an unusual particle trajectory: a particle that decayed into three muons.
“I knew immediately that this was something new and very important,” the scientist said.
“We’re seeing things we’ve never seen before; that’s what particle physics is all about. It’s very exciting.”
The trace Fowler observed (later called k) was evidence of an unknown particle that we now call the kaon or k-meson.
The k-trajectory is a mirror image of the particle previously seen by colleagues at the University of Manchester, but the trajectory followed by the UK university team breaks down into two pions, rather than three.
Trying to understand how these mirror images can be identical but behave differently helped spark a revolution in particle physics theory.
A year after the discovery, Fowler left college.
But before that, her findings were published in three academic articles, with Rosemary Brown as the lead author.
In January, Suzie Sheehy, associate professor of physics at the University of Melbourne, published an article in the professional journal Nature titled “How a forgotten physicist’s discovery broke the symmetry of the universe.”
“Seventy-five years ago, when Rosemary Brown discovered a strange particle disintegration, she set off events that would rewrite the laws of physics,” teachers there said.
Sheehy explains that the period around World War II saw a boom in particle discovery.
“In the 1930s, the number of subatomic particles expanded beyond the electron-proton duo with the discovery of the neutron, the muon (a heavier version of the electron), and the first antimatter particle, the positron.”
In this case, Fowler observed traces of grain in photographic emulsions that had been exposed to cosmic rays.
This is how physicists conducted research in the field of “exotic high-energy particles” before the advent of powerful particle accelerators.
Fowler knew what he had discovered, but according to Sheehy, it took particle physicists years to figure out the “why” of his discovery.
“When they finally found it, they shattered the idea that the laws of nature operated in some symmetrical way, with consequences that continue to this day.”
In 1956, Sheehy says, a group of particle physicists met in the United States to “discuss exactly what was going on with kaons and other particles behaving strangely”.
Fowler’s discovery led to a rethinking of the fundamental symmetries of nature.
This gives us “one of the most important experiments of the 20th century,” said Miguel Ángel Vázquez-Mozo, a theoretical particle physicist and professor at the Department of Fundamental Physics at the University of Salamanca.
Among those who attended the meeting were physicists Tsung-Dao Lee and Chen-Ning Yang, who proposed a hypothesis related to the concept of conservation of parity.
“They propose that natural systems of elementary particles sensitive to the weak nuclear force behave differently from systems of particles with identical properties reflected in an imaginary mirror, or more appropriately, from those rotated 180 degrees,” said Manuel Lozano Leyva, professor of atomic and nuclear physics and emeritus professor at the University of Seville, in a 2022 BBC Mundo article.
This is a bold idea, according to the American Physical Society (APS), because since 1925 physicists have assumed that our world is indistinguishable from its mirror image, and popular scientific theories reflect this assumption.
But Li and Yang said no one had tested it experimentally.
In 1956, they issued a challenge to experimental physicist Chien-Shiung Wu, who accepted the challenge and made history by implementing it.
“Wu’s experiment proves that there are certain phenomena in the subatomic world that are impossible when we see them in a mirror,” Vásquez-Mozo said in the same article.
“This is why parity symmetry is not preserved in elementary particle physics.”
In 1964, the concept of spontaneous symmetry breaking emerged, which Sheehy pointed out indicated the existence of the Higgs boson.
With the discovery of bosons, the so-called Standard Model was completed in 2012, which is by far the most accepted theory among scientists explaining the makeup of the universe.
*PA Media’s Nina Massey contributed to this article.
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