The story of the physicist who, after 75 years of his work, finally received his doctorate

75 years ago, Rosemary Brown “identified a strange particle decay.”

In doing so, he helped change nothing more and nothing less than our understanding of physics.

In 1948, she was a young PhD student at the University of Bristol in the United Kingdom.

After marrying fellow physicist Peter Fowler in 1949, she decided to leave her career to devote herself to her home.

She changed her maiden name and took that of her husband, with whom she had three children.

Several decades later, someone would bring him news that he had not expected.

This week, at the age of 98, his former university awarded him an honorary doctorate.

The institution’s chancellor, Paul Nurse, praised her “intellectual rigor and curiosity,” adding that she “paved the way for crucial discoveries that continue to shape the work of physicists and our understanding of the universe.”

Fowler’s discovery of the kaon particle helped predict particles like the Higgs boson.

In fact, the verification of the existence of the Higgs boson, which took place at CERN in Switzerland in 2012, is one of the greatest achievements of modern physics.

Finding the kaon particle contributed to a revolution in the theory of particle physics.

After receiving the award at a private graduation ceremony near her home in Cambridge, the doctor said she felt “very honoured” but added: “I have not done anything since then that deserves special consideration.”

Nurse, who won the Nobel Prize in Medicine in 2001 along with Leland Hartwell and Tim Hunt, was in charge of presenting him with an honorary doctorate in Science.

Fowler was born in Suffolk in 1926 and grew up in Malta, Portsmouth and Bath as his family travelled for his father’s work as an engineer in the Royal Navy.

At school, Rosemary found that “maths and science were easy, writing essays was hard.”

In 1948, the Bristol cosmic ray physics team, led by Professor Cecil Powell, was searching for new fundamental particles.

They had already found the pion (a type of subatomic particle) for which Professor Powell would receive the Nobel Prize in 1950.

At the time, when he was just 22, Fowler noticed something unusual when observing particle tracks: a particle that had decayed into three pions.

“I knew right away that this was something new and that it would be very important,” the scientist said.

“We were seeing things that had never been seen before; that’s what particle physics was all about. It was very exciting.”

The trace that Fowler looked at, later named k, was evidence of an unknown particle, which we now call the kaon or k meson.

The k-particle was the mirror image of a particle seen earlier by colleagues at the University of Manchester, but the track the team at the British university followed broke down into two pions, not three.

Trying to understand how these mirror images were the same but behaved differently helped spark a revolution in particle physics theory.

A year after the discovery, Fowler left the university.

But before that, her findings had been published in three academic papers, with Rosemary Brown as the first author.

In January, Suzie Sheehy, associate professor of physics at the University of Melbourne, published an article in the journal Nature entitled How a forgotten physicist’s discovery broke the symmetry of the Universe.

“When Rosemary Brown identified a strange particle decay 75 years ago, she set in motion events that would rewrite the laws of physics,” the professor says there.

Sheehy explains that the period before and after World War II saw a boom in particle discovery.

“In the 1930s, the list of subatomic particles grew beyond the duo of the electron and proton, with the discovery of the neutron, the muon (a heavier version of the electron), and the first antimatter particle, the positron.”

In this context, Fowler observed traces of particles in photographic emulsions that had been exposed to cosmic rays.

This was how, before the development of powerful particle accelerators, physicists conducted their research in the field of “exotic high-energy particles.”

Fowler knew what he had found, 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 adhere to certain symmetrical ways of working, with repercussions that continue to this day.”

Sheehy says that in 1956 a group of particle physicists met in the United States “to discuss exactly what was going on with kaons” and other particles that were behaving strangely.

Fowler’s discovery had caused the idea of ​​the fundamental symmetry of nature to be reconsidered.

That brings us to “one of the most important experiments of the 20th century,” according to theoretical particle physicist Miguel Ángel Vázquez-Mozo, a professor in the Department of Fundamental Physics at the University of Salamanca.

Among those attending the meeting were physicists Tsung-Dao Lee and Chen-Ning Yang, who formulated a hypothesis related to the notion known as conservation of parity.

“They argued that fundamental particle systems in nature, sensitive to the weak nuclear force, behaved differently from those with equivalent properties reflected in a hypothetical mirror or, more appropriately, rotated 180 degrees,” said Manuel Lozano Leyva, professor of Atomic and Nuclear Physics and Emeritus Professor at the University of Seville, in a BBC Mundo article from 2022.

According to the American Physical Society (APS), it was a bold idea, since since 1925, physicists had assumed that our world is indistinguishable from its mirror image and mainstream scientific theory reflected that assumption.

But what Lee and Yang pointed out is that no one had tested it experimentally.

In 1956, the challenge was proposed to experimental physicist Chien-Shiung Wu, who took it up and, in doing so, made history.

“What Wu’s experiment showed is that there are certain phenomena in the subatomic world that are impossible when seen in a mirror,” Vázquez-Mozo said in the same article.

“This is why parity symmetry is not preserved in elementary particle physics.”

In 1964, the notion of spontaneous symmetry breaking emerged, which, Sheehy says, pointed toward the existence of the Higgs boson.

With the discovery of the boson in 2012, the so-called Standard Model was completed, which is still the theory most accepted by scientists to explain what the universe is made of.

* PA Media’s Nina Massey contributed to this article.

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