Scientists at CERN observe ultra-rare particle decay process, hinting to physics beyond the standard model
The NA62 experiment at CERN, backed by researchers from Lancaster University, has observed a rare decay process, happening in less than one in ten billion charged kaons. This discovery, presented at a CERN EP seminar on September 24, 2024, may shed light on new physics, taking us closer to breakthroughs in particle interactions beyond the Standard Model.
Image credit: CERN
- First-ever ultra-rare kaon decay was observed, occurring in fewer than one in ten billion kaons.
- Potential new physics is indicated by a decay rate 50% higher than Standard Model predictions.
- The upgraded NA62 experiment allowed a 50% higher signal detection rate, leading to this discovery.
Scientists at CERN, including researchers from Lancaster University, have reported the first-ever detection of an ultra-rare decay process. The findings were presented at a CERN EP seminar on September 24, 2024. The NA62 collaboration, involving institutions such as the Universities of Lancaster, Birmingham, Bristol, and Glasgow, experimentally observed the decay of a charged kaon into a charged pion, accompanied by a neutrino-antineutrino pair.
This decay process is extraordinarily rare. It occurs in fewer than one in ten billion kaons, making it the rarest decay ever measured at the 5-sigma level.
Achieving a 5-sigma result, the threshold for declaring a discovery in particle physics, the team successfully measured the decay rate with 25% relative precision.
The latest result is based on data collected by the NA62 experiment from 2021 to 2022, combined with an earlier dataset from 2016 to 2018. The success of the 2021 – 2022 dataset can be attributed to upgrades in the NA62 setup.
These upgrades allowed the experiment to operate at 30% higher beam intensity and utilize more advanced detectors, enabling the researchers to collect signal candidates at a 50% higher rate than previously possible.
Additionally, new tools were implemented to better suppress background signals, further enhancing the precision of the analysis.
The NA62 experiment was specifically designed to measure the ultra-rare decay. Kaons are produced by a high-intensity proton beam from the CERN Super Proton Synchrotron (SPS) colliding with a stationary target, generating a beam of almost 1 billion secondary particles, including about 6% charged kaons, which fly through the NA62 detector.
The system can identify and measure each kaon and its decay products, except for neutrinos, which manifest as missing energy in the detector.
“The rarer the decay, the more sensitive it is to possible effects of new physics. This is because we know that new physics must produce small effects at the accessible energies; otherwise, we would have discovered it already,” said Dr. Karim Massri, a Lecturer in Physics at Lancaster University and the NA62 Physics Coordinator.
Massri added that while more data is required to uncover hints of new physics, “this result is a leap forward and further strengthens the strong interest in future results from NA62.”
“This is the culmination of a decade of work. Looking for effects in nature that occur about once in ten billion trials is fascinating and challenging,” said Professor Giuseppe Ruggiero, the current NA62 spokesperson from the University of Florence.
The primary motivation behind studying such ultra-rare processes lies in their potential to reveal physics beyond the Standard Model, the current framework used to understand particle interactions.
Although the observed decay is consistent with the Standard Model’s predictions, the measured decay rate is approximately 50% higher. This deviation may suggest the presence of new particles influencing the process, though further data is needed to confirm this possibility.
With data collection ongoing, NA62 will be able to confirm the existence of contributions to the decay from new physics or place strong constraints on the size of any such possible contributions.
References:
1 NA62 experiment at CERN reports first observation of ultra-rare process that could uncover new physics – Lancaster University – September 24, 2024
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