Antimatter factory at CERN: a breakthrough with a Hungarian contribution

In the experiment antiprotons were trapped in helium atoms, thus replacing one of the electrons. The scientists managed to cool down nearly 2 billion long-lived antiprotonic helium atoms to absolute temperatures of 1.5-1.7 K and to effectively eliminate thermal movement in order to greatly improve the precision of the laser spectroscopic measurements. The antiprotonic helium atom is of an especially unique quality: the helium nucleus binds an electron and an antiproton, so it contains a particle and an antiparticle at the same time, creating such a physical state and resulting in a life span long enough to allow for the spectroscopic measurements of its atomic transitions.

The novel achievement of the collaboration is that it managed to surround the studied antiprotonic atoms with extremely cold helium gas. In the antiprotonic helium atom, the electron is in an orbit of much greater radius than the antiproton, therefore, in collisions with cold gas atoms, it is capable of cooling down without the antiproton being captured in the nucleus and radiating away. The latter occurs only if the antiproton is successfully degenerated as resonance by the use of an appropriately tuned laser. This is how transition energy is measured, from which mass can be defined with high precision. The experiment, with data collected between 2010 and 2014, confirmed the symmetry between matter and antimatter, as the mass of the antiproton and that of the proton turned out to be identical to more than ten digits of precision.

Two Hungarian contributors to the ASACUSA experiment, Dániel Barna and Anna Sótér Source: MTA Wigner Research Centre for Physics