Surprising behavior of hybrid matter: Antimatter atoms in superfluid helium

A hybrid matter with an antimatter helium atom and an antiproton, the antimatter equivalent of an electron, has an unexpected response to laser light. The result, described in a paper published today in the journal Nature, may open doors to several lines of research.

Masaki Hori says that the study suggests that hybrid matter could be used in more than just particle physics.

To determine the antiproton's mass and compare it to that of the protons, the ASACUSA collaboration makes hybrid matter. These hybrid atoms contain an antiproton and an electron around the helium nucleus, instead of two electrons around a helium nucleus, and are made by mixing antiprotons produced at the antimatter factory with a helium gas that has a low atomic density.

Antimatter studies involve measuring the response of the hybrid atoms to laser light in order to determine their light spectrum, and low gas densities and temperatures have played a key role. The mass of the antiproton relative to that of the electron is determined by the transitions of the antiproton between energy levels.

The ASACUSA researchers were surprised to see a decrease in the width of the antiproton lines when they used liquid helium, which has a much higher density than gaseous helium.

They found an abrupt further narrowing of the lines when they decreased the temperature of the liquid to values below the temperature at which the liquid becomes a superfluid.

The behavior of the hybrid was unexpected, according to Anna S, who is now an assistant professor at ETHZ.

The researchers think that the behavior observed is related to the distance between the electronic orbital and the hybrid helium atom. When a laser light is shone on a hybrid atom, it does not change the electronic orbital of the atom, even if the atom is immersed in superfluid helium. Further studies are needed to confirm this hypothesis.

There are several ramifications of the result. To study their response to laser light in detail, researchers may create other hybrid helium atoms, such as pionic helium atoms, in superfluid helium using different antimatter and exotic particles. The narrowing of the lines in superfluid helium suggests that hybrid helium atoms could be used to study this form of matter. The narrow lines could be used to search for antiproton or antideuterons that hit the liquid or superfluid that is used to cool experiments in space. There are many technical challenges that need to be overcome before the method becomes compatible with existing techniques.

More information: Anna Sótér et al, High-resolution laser resonances of antiprotonic helium in superfluid 4He, Nature (2022). DOI: 10.1038/s41586-022-04440-7 Journal information: Nature Citation: Surprising behavior of hybrid matter: Antimatter atoms in superfluid helium (2022, March 17) retrieved 17 March 2022 from https://phys.org/news/2022-03-behavior-hybrid-antimatter-atoms-superfluid.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.