Researchers discover the heaviest antimatter hypernucleus ever observed

The STAR Collaboration, an international team of scientists using the STAR detector at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC), has announced the first observation of an antimatter hypernucleus, antihyperhydrogen-4. Published in Nature, the research describes the hypernucleus, the heaviest antimatter hypernucleus found to date. It is composed of an antiproton, two antineutrons, and one anti-Lambda hyperon.

The pop science field has dubbed antimatter as a sort of “evil twin” of normal matter because the two are surprisingly similar, only differing in charge. If the two come into contact, they mutually destruct in burst of energy.

The RHIC is a powerful enabler of physics experiments

RHIC, a facility capable of accelerating heavy ions to near the speed of light and colliding them to mimic the extreme energy densities “microseconds after the Big Bang, with comparable amounts of matter and antimatter,” as the researchers noted in Nature. The RHIC’s track record in studying strange makes it an ideal tool for investigating antihyperhydrogen-4, which contains an anti-Lambda hyperon.

Matter vs. antimatter

The study of antihyperhydrogen-4 offers a deeper glimpse into the symmetry between matter and antimatter, a fundamental question in particle physics. “What caused the difference in quantities of matter and antimatter in the universe? To answer this question, an important approach is to create new antimatter in the laboratory and study its properties,” asked Prof. QIU Hao from IMP, in a press release.

In the recent study, the scientists describe comparing the lifetimes of antihyperhydrogen-4 with its matter counterpart, hyperhydrogen-4. They foundno significant differences within the precision of their measurements. The finding supprts the fundamental symmetry between matter and antimatter, a core principle in the standard model of particle physics. The research also paves the way for future study of antihyperhydrogen-4, which could shed more light on matter-antimatter asymmetry.

Researchers at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences, led the research, which involved identifying a signal of roughly 16 antihyperhydrogen-4 events from the decay products, antihelium-4 and a π+ meson. In the scope of the research, the scientists analyzed a dataset involving some 6.6 billion heavy-ion collision events.

Timeline of notable antimatter advances

Year	Milestone	Description
1928	Theoretical Prediction	Paul Dirac proposes the concept of antimatter in his relativistic quantum theory of the electron.
1932	Positron Discovery	Carl Anderson discovers the positron (antielectron) while studying cosmic rays.
1955	Antiproton Discovery	Emilio Segrè and Owen Chamberlain discover the antiproton using the Bevatron particle accelerator.
1956	Antineutron Detection	Bruce Cork and colleagues detect the antineutron.
2000	CERN’s Antiproton Decelerator	Facility established for producing and studying low-energy antiprotons.
2010	ALPHA Experiment	First successful trapping of antihydrogen atoms for extended periods at CERN.
2011	AMS-02	Alpha Magnetic Spectrometer installed on the ISS to search for cosmic antimatter and dark matter.
2013-2014	BASE Experiment	CERN approves BASE project (2013). First high-precision measurement of proton magnetic moment and antiproton measurements begin (2014).
2024	Antihyperhydrogen-4 Observation	STAR Collaboration announces first observation of antihyperhydrogen-4, an antimatter hypernucleus, using the STAR detector at Brookhaven National Laboratory’s RHIC.