Something Weird Just Happened That We Can't Really Explain With Existing Physics

• Do kaons decay using a new kind of physics? Researchers are trying to explain their anomalous findings.
• Their larger experiment is an ongoing investigation of CP symmetry.
• The anomalies could be measurement noise, a new kind of particle, or a new physical force.

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Scientists have proposed a new kind of subatomic particle to explain another particle’s mysterious disintegration. The kaon, a special case of meson particle, is made of one quark and one antiquark. All are part of the overall family called hadrons. When kaon particles decay, a very rare few undergo a change that has baffled scientists. Can it be explained by existing physics at all?

Many mesons were discovered because they themselves are the results of decay of other materials, and in turn, they decay into different particles like types of protons and neutrinos. Each meson has a set of possible decay outcomes, and scientists have only recently begun to fully probe and explore the full range of what these possibilities are. And since scientists invent and fine-tune better observation tools all the time, we live in a very particular golden age of discovery of meson decay outcomes.

If this kaon decay (de-kaon?) is validated, it represents something new in physics. The style of decay could indicate a new kind of particle altogether, or a new physical force at work to make the novel decay. The idea of “new physics” sounds either scary or outlandish depending on your outlook, but in the current explosive age of observation of quantum phenomena and subatomic particles, it’s not uncommon for researchers to wonder if what they see represents something previously unheard.

Kaons have several known common ways of decaying, but the one in this paper is so rare that scientists weren’t sure it existed before now. Their model predicted they’d see less than a quarter of one instance of this decay in their sample—not four, which is a veritable fortune by comparison. What does it mean to see so many more instances?

“If confirmed, this requires physics beyond the standard model to enhance the signal. We examine various new physics interpretations of the result including these: (1) heavy new physics boosting the standard model signal, (2) [...] a new light long-lived particle, or (3) reinterpretation of the whole signal as the production of a new light long-lived particle at the fixed target,” the scientists explain in the paper.

In other words, the high number of “fluke” measurements was itself a sign that something unusual was going on, and now scientists want to understand and explain why it happened. Yes, the results could be “noise,” or just interference or measurement errors. Our instruments for measuring subatomic particles are often using secondary information, like the shadow an object casts or the way it reflects light instead of the object itself.

Because of the extreme tininess at play, these secondary data can be inconclusive. That’s why the next step for this research team is to try to definitively rule out noise. Researcher Kohsaku Tobioka says even this level of noise (if it’s so) would be wild. “In this case, expectation of noise is very low, so even one event or observation is very striking,” Tobioka says. “And in this case, there were four."