Belle II detector produces world’s most precise measurements of subatomic particle lifetimes
Particle lifetime measurements with early data from the Belle II experiment at the SuperKEKB accelerator demonstrate the experiment’s high precision.
image: The Belle II experiment at the SuperKEKB accelerator measures particle interactions with extreme precision. Collisions of electron and positron beams create the high-energy environment needed to produce subatomic particles that do not otherwise exist in nature.
Credit: Image courtesy of Felix Metzner, KIT.
The Science
Scientists believe that subatomic particles called quarks and leptons (such as electrons and neutrinos) are the building blocks of all visible matter in the universe. However, at very high energy levels, similar to the conditions soon after the Big Bang, scientists can produce particles containing different types (or flavors) of quarks, although they decay very quickly. The new Belle II experiment recently made a world-leading measurement of the lifetime of one such particle. This demonstrates the experiment’s ability to make the extremely precise measurements. Scientists need this level of precision in their quest to discover new particles and interactions.
The Impact
Researchers can use the Standard Model of Particle Physics to make very accurate predictions about how subatomic particles interact and decay. However, there are gaps in the Standard Model that indicate other particles and interactions that have never been observed. Researchers want to fill these gaps to better explain how our universe developed. Many extensions of the Standard Model attempt to resolve these inconsistencies. However, these extensions rely on approximations of the complicated interactions of subatomic particles. Those approximation methods can also be used to predict particle lifetimes. Precise measurements of particle lifetimes from the Belle II experiment therefore provide stringent tests of theoretical predictions beyond the Standard Model.
Summary
Using the new, state-of-the-art detector, the Belle II experiment reported a world-leading measurement of the Λ+𝑐 charmed baryon using the weak decay Λ+𝑐→pK-π+. This result will be useful for providing stringent tests of theoretical methods that are used to make predictions for new particles and interactions beyond the Standard Model.
This result also shows the power of the Belle II detector at the SuperKEKB accelerator to make extremely precise measurements. In particular, this measurement is highly sensitive to the calibration and alignment of detector components and therefore provides a probe of these components. This is especially true for the innermost detector component, which is made of silicon pixels to improve the resolution with which particle decays can be identified and measured. Thanks to the detector upgrades, Belle II was able to make the most precise measurement of the lifetime of the Λ+𝑐 particle, using only a small fraction of the total data sample to be collected over the life of the experiment. Early measurements like these provide proof that the Belle II experiment will be able to continue making extremely precise measurements that have the potential to expose the existence of unidentified particles and interactions.
Funding
Supported by the Department of Energy Established Program to Stimulate Competitive Research (EPSCoR) program and the Office of Science, Office of High Energy Physics.