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Researcher Awarded ERC Consolidator Grant to Study Neutron Skins

An ERC Consolidator Grant for 2.55 million Euros has been awarded by the European Research Council to Alexandre Obertelli, a researcher at the Department of Physics, which will support him for five years. This will expand the research works of TU Darmstadt into antimatter, in the experimental nuclear physics area.

The reputed ERC Consolidator Grant for Alexandre Obertelli is related to the “PUMA—antiProton Unstable Matter Annihilation” project, the aim of which is to analyze neutron halos and neutron skins, which are identified by the creation of low-density, pure neutron matter at the surface of neutron-rich radioactive nuclei. PUMA will devise a novel method for probing the tail of the nuclear density that has the antimatter.

One of the most intriguing quantum phenomena occurring in nature is the development of neutron skins and neutron halos in atomic nuclei. To date, thick neutron halos and skins have not been observed in medium mass nuclei, that is, nuclei including more than 20 nucleons. They would be distinctive, low-density neutron matter obtainable in the laboratory.

Investigation of these will highly improve man’s understanding of nuclear structure and the nuclear equation of state, closely related to the neutron star structure. The aforementioned basic phenomena, linked to the variance of protons and neutron in unstable nuclei, are crucial to gain an in-depth knowledge of the complicated nature of nuclei, nuclear matter and associated astrophysical processes.

As part of the PUMA project, Alexandre Obertelli and his colleagues will evaluate the neutron over proton densities in the matter density distribution tail in short-lived radioactive nuclei, to reveal and analyze neutron halos and skins. To answer these two nuclear structure questions, PUMA examined an innovative methodology to investigate radioactive nuclei developed at lower kinetic energies - antiproton interaction with unstable nuclei. The basic concept is to compute the number of antiproton-produced annihilations of protons and neutrons. Till date, this strategy has not been devised anywhere.

PUMA is based on innovative equipment: a transferable trap for storing antiprotons and increasing their interaction with slow, rare isotopes to initiate annihilations and to evaluate the ensuing radiation. The PUMA approach includes two steps: first, the antiproton storage will be carried out at the new low-energy antiproton facility ELENA at CERN. Second, the antiprotons will be transferred to the ISOLDE facility of CERN (located only a few hundred meters from ELENA) at which slow radioactive nuclei are synthesized.

In 2005, Alexandre Obertelli defended his Ph.D. thesis at the Paris-Sud University, France. In 2006, he was recruited by the Commissariat à l’Energie Atomique (CEA) as a staff physicist in France, where he developed his study on the spectroscopy of radioactive nuclei.

He received his first ERC grant in 2010 for in-beam gamma spectroscopy at the RIBF, RIKEN, Japan. The study was based on an innovative device to enable the spectroscopy of short-lived nuclei synthesized in smaller amounts. After receiving his second ERC grant for PUMA, Alexandre Obertelli joined TU Darmstadt to continue his study.

Alexandre Obertelli has authored over 100 scientific articles and is a member of the physics advisory committees of the radioactive heavy-ion beam facilities GANIL in France, RIBF, and RCNP in Japan and of the scientific council of IPN Orsay, France. Also, on January 1, 2018, he joined the SPSC (SPS and PS Experiments Committee) of CERN. In addition to CERN, he aspires to take part in developing the physics program at GSI/FAIR in the near future.

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