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| Dr. Roman Gernhäuser from the TUM Physics Department is part of the international research team that detected the tetra-neutron. Image Credit: Uli Benz / TUM |
After 60 years of unsuccessful searches, an international research team has discovered a neutral nucleus for the first time – the tetra-neutron. The collaboration succeeded in creating an isolated four-neutron system with low relative kinetic energy in a volume equivalent to an atomic nucleus.
The building blocks of atomic nuclei are the nucleons, which come in two types, the neutral neutrons and the positively charged protons – the two so-called isospin states of the nucleon. Bound nuclei composed exclusively of neutrons have never been clearly identified. The only known bound systems that consist almost exclusively of neutrons are the neutron stars. These are the final stages of stellar evolution with a typical diameter of about ten kilometers. These stars are stable (bound) by gravity, which leads to a very high neutron density inside the stellar corpses. Atomic nuclei, in turn, are bound by the strong interaction, with preference to bind a comparable number of neutrons and protons – this is known from the stable nuclei found on Earth.
However, the study of pure neutron systems is of great importance, since this is the only way to gain experimental knowledge about the interaction of several neutrons with each other and thus about the nuclear interaction. Moreover, the study of the hitherto hypothetical particles could help to better understand the properties of neutron stars. Finding out whether such neutron systems exist as resonance states or even bound nuclei is therefore a long-standing endeavor in nuclear physics. The international team of scientists has now made a new attempt to do this, using a new experimental method that differs from all previous experiments.









