Transfer reaction as a probe of multi-neutron systems and few-nucleon correlations: An overview of MUGAST campaign and the search of isobaric analog state of the tetra-neutron in hydrogen-4

par Quentin Délignac

vendredi 6 nov. 2026, 11:15 → 13:15 Europe/Paris

Through this seminar, I aim to present in a first part, the state-of-the-art of MUGAST
campaign performed at GANIL on LISE spectrometer. I will talk about the present status
of the campaign, the experimental setup and the perspectives with it.
In a second part, I will present the recent search of the isobaric analog state (IAS)
of the tetra-neutron in hydrogen-4. The existence of tetra-neutron (4n) has been a long-
standing question in nuclear physics and few-body neutron systems are of great interest for
understanding nuclear forces and the structure of neutron-rich matter. Since the beginning
of the century, the discovery of possible candidate for the 4n state, has been reported
several times. However, it triggered a lot of debate about the theoretical interpretation of
the results. Assuming that the 4n state observed is a (T=2, Tz =2) and due to the isospin
symmetry, it should exist an isobaric analog state (IAS) (T=2, Tz =1) in 4H nuclei. We
proposed to study indirectly the 4n system via the IAS in 4H nuclei through 6He(p,3He)4H
reaction. If such a state is observed, it will allow to add more input to current theoretical
description of neutral nuclei.
The experiment was performed at GANIL facility using the LISE spectrometer in 2025
beam time. A secondary beam of 6He at 50 MeV/u was produced by fragmentation of
a primary beam of 13C at 60 MeV/u on a Be target. The beam was transmitted to the
experimental setup consisting of a reaction target (CH2 at 10 mg/cm2) placed in the
center of the four MUST2 telescopes (Silicon strip detectors coupled to CsI scintillators)
and a simplified Zero Degree Detection with only plastic scintillators supplemented by a
plastic scintillator placed upstream the target for normalization.
Both results from 6He(p,t)4He useful for calibration purpose and from 6He(p,3He)4H
will be presented. For the latter, the decay products of 4H are identified in MUST2 so
that the excitation energy spectrum for each decay channel have been extracted. They
will be compared with phase space calculations. Preliminary results concerning the IAS
of the 4n will be presented.