Scientists have discovered a rare type of atomic core that contains an unusual flavor of quark in one of its nuclear particles. The discovery was made using the Large Hadron Collider (LHC), the world’s largest and most powerful particle accelerator.
What are hypernuclei and why are they important?
Hypernuclei are atomic cores that contain hyperons in addition to protons and neutrons. Hyperons are baryons, which are particles made up of three quarks, but unlike protons and neutrons, they contain at least one strange quark. Strange quarks are heavier and more unstable than the up and down quarks that dominate ordinary matter.
Hypernuclei are very rare and short-lived, as they decay into lower-mass particles in a matter of picoseconds (one trillionth of a second). They are of great interest to physicists, as they can reveal new insights into the strong nuclear force that binds quarks together, as well as the exotic states of matter that may exist inside neutron stars, the dense remnants of collapsed stars.
How did the scientists detect hypernuclei?
The scientists used a new technique to detect hypernuclei in the data collected by the Large Hadron Collider beauty (LHCb) experiment between 2016 and 2018. The LHCb experiment is one of the four main detectors at the LHC, and it specializes in studying particles that contain bottom quarks, another heavy and unstable flavor of quark.
The scientists looked for hypertriton, a type of hypernucleus that consists of a proton, a neutron, and a Lambda hyperon. They did not detect hypertriton directly, but rather its decay products: an antiproton and a positively charged pion. The pion escapes from the nucleus, while the antiproton remains trapped inside, transforming the hypertriton into antihelium.
The scientists identified more than 100 hypertriton and antihypertriton candidates in the data, with a statistical significance of more than five standard deviations, meaning that the chance of a false positive is less than one in 3.5 million. This is the first time that hypernuclei have been detected at the LHC, and the largest sample of hypernuclei ever observed in a single experiment.
What are the implications of the discovery?
The discovery of hypernuclei at the LHC opens up new possibilities for studying the properties and interactions of these exotic particles. The scientists hope to measure the mass and lifetime of hypertriton with higher precision, as well as to search for other types of hypernuclei, such as those that contain two or more strange quarks.
The discovery also has implications for astrophysics, as it could help explain the origin of antihelium nuclei that have been tentatively detected in cosmic rays by several experiments. Antihelium nuclei are extremely rare in nature, as they are expected to be annihilated by collisions with normal matter. One possible source of antihelium nuclei is the decay of antihypernuclei that are produced in high-energy collisions between cosmic rays and interstellar gas.
The scientists plan to continue their search for hypernuclei and antihypernuclei in the next run of the LHC, which is scheduled to start in 2025 after a major upgrade. They also hope to collaborate with other experiments at the LHC and elsewhere to compare their results and improve their understanding of these fascinating particles.