Discovery of a rare decay of a Kaon particle
A possible hint for new physics beyond the standard model of particle physics?
The NA62 experiment at CERN has detected a very rare decay of a Kaon particle for the first time. The particle process was predicted theoretically, is now statistically confirmed and thus experimentally proven. The Max Planck Institute for Physics is involved in the experiment with a working group.
The initial particle in the observed decay is a charged kaon, which consists of two elementary quarks. It had been predicted that kaons can decay into a charged pion - also a pair of quarks - and two neutrinos. The theory's calculations also showed that decay is extremely rare - only one in 10 billion kaons undergoes this process. The scientists of the NA62 experiment have now proven the existence of this decay.
But why is this detection so important? The structure of matter and the interactions of elementary particles are considered to be well researched and are anchored in the so-called standard model of particle physics. However, there are numerous phenomena that cannot be explained with the physics we know today. Scientists are therefore looking for processes that are new and deviate from the standard model.
The current discovery could offer just such a surprise. The decay itself “fits” the standard model, but it occurs somewhat more frequently than would be expected. One explanation for this could be that a new, previously undiscovered particle has a hand in this: It could act as a kind of catalyst and increase the probability of decay. This possibility can only be tested with further measurements with NA62. In a few years' time, the experiment should provide sufficient data to confirm or rule out new physics.
The measurements with the NA62 detector have been running since 2016. The decay of the kaon into one pion and two neutrinos had already been measured, but the earlier data was not sufficient to statistically substantiate the result. Only with the recently analyzed measurement data from the years 2021 and 2022 was sufficient data available to statistically confirm the result with a significance of 5 sigma - and thus to prove it experimentally.
The NA62 experiment uses the proton beam in the Super Proton Synchrotron accelerator ring at CERN. The high-energy protons are fired at a fixed target and transform into other particles in the process. These secondary particles fly into the NA62 detector. 6 percent of them are kaons, whose decay products are precisely measured and analyzed. The MPP group is participating in the NA62 experiment via the ERC Starting Grant “AxScale” and the Lise Meitner Group “In search of new, lightweight physics”. It focuses in particular on the analyses of the data obtained with NA62.
