When news broke that Prof. Luk Kam Biu had been elected to the U.S. National Academy of Sciences (NAS), his reaction was understated.
“Knowing the high caliber of the NAS members, I was humbled by the news and am excited to join the club,” says Prof. Luk, who has been at the forefront of particle physics for decades.
But behind this quiet, unassuming nature lies a career defined by bold questions, meticulous experimentation, and discoveries that have reshaped our understanding of the subatomic world.
Matter is the Matter
Because NAS nominations are anonymous, Prof. Luk can only speculate which work drew the Academy’s attention.
“If I have to guess, it is likely related to the discovery of this new kind of neutrino oscillation in the Daya Bay Reactor Neutrino Experiment that I initiated and have co-led since its inception,” he notes.
Their experiment captured something physicists had long theorized about but had never definitively observed: a new mode of neutrino oscillation.
It was a breakthrough that not only helped to crack the Standard Model of particle physics but also opened a critical pathway toward answering one of cosmology’s most profound questions: why does the universe consist almost entirely of matter?
Researching the Strange
It is also possible that Prof. Luk’s pioneering experimental techniques for probing the properties of the so-called “strange particles” caught the attention of those who nominated him to the august NAS body.
Several of those early studies remain world-leading decades later, and one finding remains unexplained to this day.
“One of my team’s discoveries, which ruled out all the theoretical models at the time the experiment was carried out, is still unexplained,” he reflects.
As background to this experiment, you need to know that matter is made of tiny building blocks called quarks. A stable proton, for instance, is made of two “up” quarks and one “down” quark. But when we use particle accelerators to smash protons into targets at incredible speeds, the collisions create a cascade of new, short-lived particles. Some of these contain a heavier, more unusual type of quark called a “strange” quark. Physicists call them strange particles.
Surprising, Mysterious, Unexplained
Early in his career, Prof. Luk was involved in a series of experiments studying a particular family of these strange particles, known as hyperons. His team noticed something unexpected during their experiments: when these particles were created, their internal “spins” weren’t pointing randomly. Instead, more than half of them were aligned in the same direction.
“This was surprising because the protons we were smashing together had no preferred spin direction at all.
This puzzle sparked years of theoretical work. Physicists developed models to explain the alignment, and those models made a clear prediction: any hyperon—or its antimatter counterpart—that didn’t directly inherit quarks from the original proton beam should not be aligned.
“We tested this, and sure enough, two types of antimatter hyperons came out completely random, just as the theories predicted,” he says.
He even developed a mathematical formula to measure the spin alignment of the Omega-minus hyperon—a rare particle made entirely of strange quarks—and later confirmed experimentally that it, too, showed no alignment.
“At that point, we thought we had finally cracked the case,” he says.
But nature had one more surprise in store.
“Years later, I designed a new experiment to measure the magnetic properties of the Omega-minus for the first time in history. As an unexpected side result, we discovered a completely different member of the antimatter hyperons that was significantly aligned. This finding directly contradicted every existing theoretical model,” he continues.
To this day, no one has fully explained why it happens, a humbling reminder that the universe still holds deep secrets.
Knowledge for Knowledge's Sake
Now elected to the NAS, Prof. Luk remains committed to fundamental inquiry, guided by the principle that not every discovery necessarily needs a practical justification to be worthy of pursuit. Some exist to expand the boundaries of human knowledge.
“My curiosity about nature drives my research, and it has no direct application,” he admits.
For Prof. Luk Kam Biu, the journey to the NAS has never been about chasing accolades. It was, and remains, about listening closely to the universe, and contemplating all that is strange and mysterious.
