High-precision missing mass spectroscopy of the superheavy hydrogen isotope 6H

• Applicant: Professor Dr. Josef Pochodzalla
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455063272

Considering the fact that neither a trineutron nor a tetraneutron state have been proven to exist unambiguously, heavy hydrogen nuclei 4H, 5H and even more the superheavy hydrogen isotopes 6H and 7H are closest approximations to pure neutron nuclei and also to the matter of which neutron stars are made of. They are rather simple nuclear systems and can be treated by modern ab initio nuclear structure calculations. Better than anywhere else, these nuclei probe subtle aspects of the nuclear interaction among neutrons, e.g., the role of two- and many-neutron forces.None of these exotic hydrogen isotopes has bound states. Decay spectroscopy (invariant mass studies) is feasible but often hampered by the necessity to detect several neutrons. Most experiments up to now focus therefore on missing mass studies. While resonances in 4H, 5H and even 7H seem to be well established, this is not the case for 6H. In this project we propose a new method to study the excitation spectrum of the still elusive neutron-rich hydrogen nucleus 6H. Questions which need to be answered are: Is its ground state narrow or broad? What is the mass of this ground state resonance? Are there excited states? And even -- considering the situation of the present data -- does it really exist? We will study this nucleus in a missing mass experiment via the reaction 7Li(e,e’ pi+ p) 6H* at MAMI. The three high resolution spectrometers in the A1 hall will be used to detect the scattered electron, the emitted proton and the positive pion. In a pilot experiment we have already demonstrated the feasibility to detect such triple coincidences at the A1 hall in the 12C(e,e’ pi+ p) reaction. The proposed project is made possible by the recent development of a novel Lithium target. Its special geometry enables a very high luminosity and at the same time a high resolution for the missing mass for the 7Li(e,e’ pi+ p) reaction.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Patrick Achenbach