Study of annihilations with slow extracted antiprotons


It is well known that everything we observe, from the smallest objects in our everyday lives to distant stars and galaxies, including all known life forms is made of matter. However, according to the leading theory about the creation of our universe, the Big Bang should have produced equal amounts of matter and antimatter, as particle creation out of energy can only happen in pairs. Each pair consists of a particle and its corresponding antiparticle with the same mass but opposite electric charge. When such partners come into contact again, they cancel each other out, releasing energy, as they mutually annihilate. If matter and antimatter were created and destroyed together, it seems the universe should contain nothing but leftover energy. The reason why today’s universe is dominated by matter is still one of the biggest mysteries in modern physics.

Driven by this unsolved problem, in the past few decades physicists have successfully produced and studied antimatter particles in laboratory. Today antiprotons, the antimatter counterparts of protons are routinely produced at the Antiproton Decelerator at CERN, and even antihydrogen, the only antimatter atom synthesized hitherto is being thoroughly examined in various experiments. The measurements of the different properties and interactions of antimatter particles are compared to the corresponding matter particles or to physics models, in search for subtle differences that could point to the reason why our universe is matter-filled.

The antiproton annihilation process, where an antiproton annihilates with a proton or with an atomic nucleus and new particles are produced is one of the key mechanisms in matterantimatter interaction. Moreover, the only way to detect antihydrogen in the antimatter experiments at CERN is through its annihilation. At present, the features of the very low energy antiproton annihilation with nuclei are still not well known, and the different models give different predictions.

This FWF project aims to reveal the full image of the antiproton annihilation with various atomic nuclei, by detecting all the charged particles that emerge from such interaction. This will explore some of the annihilation’s unknown traits and will help the validation of different physics models, while potentially identifying novel nuclear physics processes not yet included in these models. The measurements will take place at the ASACUSA experiment at CERN, which will be upgraded to guide very slow antiprotons towards different nuclear targets. Part of the project will be devoted to simulate and to estimate the feasibility of a new experiment in which a very rare, exotic annihilation occurring between one antiproton and helium-3 would be observed for the first time.

Project leader:

Dr. Angela Gligorova


Duration: 15/06/21 – 14/06/24

Funded by:

FWF project
P 34438-N