Research Group Alexandre Obertelli
Exotic, Strange and Anti-Matter

Welcome to the Research Group of Prof. Alexandre Obertelli

Alexander von Humboldt Professorship

We design and perform experiments to explore phenomena of many-body nuclear systems far away from the valley of the stable nuclei. These rare isotopes, with a large neutron-to-proton asymmetry, in contrast to stable nuclei, exhibit a shell structure which is still to be unravelled. Rare isotopes at the edge of being bound by the strong force, i.e., located at the proton or neutron drip line may show a thick neutron or proton skin or a halo. These properties can be investigated at dedicated Radioactive Ion Beam (RIB) facilities where short-lived nuclei are produced and studied before their radioactive decay. Many-body nuclear systems can be extended to the strangeness degree of freedom, i.e. composed not only of protons and neutrons but also of hyperons, which are baryons with at least one strange quark. The hyperon-nucleon interactions are different from the nucleon-nucleon interactions and the study of those so called hypernuclei will provide precious information on in-medium nuclear interactions.

Besides the fundamental interest in understanding the nuclear properties of the exotic nuclei, this knowledge will help to understand the synthesis of the elements in the universe in which rare isotopes play a central role. The understanding of the properties and reactions of neutron-rich nuclei as well as hypernuclei provides a path towards understanding neutron-rich and dense nuclear matter as found in neutron stars.

We base all our experiments on unique instrumentation and methods, which aim at giving access to what has been out of reach thus far. We develop systems dedicated to the spectroscopy of rare isotopes produced with very low rate at the Radioactive Isotope Beam Factory (RIBF) of RIKEN, Japan. We design a new experiment, which utilizes antiprotons from the Extra Low Energy Antiproton (ELENA) ring at CERN’s Antiproton Decelerator (AD), to probe the density tail of rare isotopes produced at CERN’s Isotope mass Separator On-Line facility (ISOLDE). And furthermore, we propose a new method for the high-resolution stereoscopy of hypernuclei at GSI/FAIR. These projects are carried within international collaborations.