Subatomic particles are a gateway into a world of mystery and uncertainty. In this fuzzy land, our usual assumptions about matter and energy are turned upside down. At this level, the laws of physics begin to change and matter as we know it ceases to exist.
In 2013, two teams of scientists working independently in Japan and China established the existence of a new subatomic particle with unusual characteristics. This happened during explorations designed to elicit further information about a particle known as Y(4260), which was freshly discovered in 2005. The Y(4260) particle didn’t seem to fit with existing models, suggesting there was more going on in the subatomic realm than physicists had previously suspected.
When studying the decay of Y(4260) more deeply, a further surprise was uncovered. Scientists working in each team found an unexplained burst of energy that was equivalent to the weight of a proton (remember, in quantum physics matter and energy are interchangeable). From this anomaly, they were able to deduce the existence of a brand new particle they labeled Z(3900).
Because it was four times as large as a proton, they realized it must be made up of four quarks, which makes it the first four-quark particle, or tetraquark, ever discovered. This experimental result was repeated more than 400 times, proving that the Z(3900) is real and the findings of the scientists were authentic.