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\section{Introduction}
\section{Introduction}
The search for the the multineutron systems is one of the most attractive fields of modern nuclear physics.
The first suggestion about the stability of such systems was made in works \cite{Zeldovich:1960,Goldansky:1960}, but multiple experimental attempts of search for bound states of the neutron clusters (e.g. 2n in Ref.\ \cite{WILLARD1964339}, 3n in Ref.\ \cite{belozyorov:1988}, 4n in Ref.\ \cite{Marques_PhysRev:2002,Kisamori:2016}) were unsuccessful.
Never the less, the issue of bound neutron nuclei existence is still addressed in the modern theoretical works, see Ref.\ \cite{Pieper:2003,Timofeyuk:2003b,Higgins:2021}.
The recently published work \cite{Duer:2022} reported the observation of the resonance at 2.37\,MeV with $\Gamma=1.75$\,MeV, which was interpreted as a tetraneutron state produced in a high-energy knockout reaction of alpha core from the $^8$He beam.
The ensuing theoretical work \cite{Lazauskas:2023} provides the possible realistic explanation of observed phenomenon using the model based on a transition between initial and final state of four studied neutrons.
The published in Ref.\ \cite{Duer:2022} results are undoubtedly convincing but the used reaction of knockout of the alpha core from the $^8$He was studied only at very backward angles.
Moreover, authors summarized that the obtained results are limited by the single approach of four-neutron system production and do not describe the correlation of the component neutrons.
This work is dedicated to the results on the $^2$H($^8$He,$^6$Li) reaction studied at forward angles at ACCULINNA-2 fragment separator.
\section{Experiment}
\section{Experiment}
ACCULINNA-2 facility, FLNR, JINR, produced 26\,AMeV $^{8}$He and focused it on the cryogenic deuterium target.
The detection system was intended to measure the product of the $^2$H($^8$He,$^4$He)$^6$H reaction and further $^6$H$\rightarrow^3$H+3n decay.
The employed detector system is described in Ref.\ \cite{Nikolskii:2022}.
For the particle identification (PID) of the beam two plastic scintillators were used, which allowed to measure the energy of the projectile from its time-of-flight (ToF) and identify the isotope by the dE-ToF method.
%The particle identification (PID) of the beam was performed by the dE-ToF
%For the beam particle identification and its energy determination two plastic scintillators were used.
The trajectories the beam projectiles were tracked by two pairs of multi-wire proportional chambers.
The cryogenic target was filled with a deuterium gas at 27\,K of atmospheric pressure.
For the detection of the charged reaction products two types of $\Delta E$-$E$ telescopes were used.
The side assembly of three (20\,$\mu$m, 1\,mm and 1\,mm thick) silicon strip detector (SSD) telescope, and the front telescope made of the 1.5\,mm double side SSD coupled to the CsI(Tl) scintillator array.
The thin, 20\,$\mu$m detectors in the side telescopes allowed one to reliably identify and reconstruct low-energy particles (the recoil $^4$He nuclei with energy $\ge$5\,MeV), see Ref.\ \cite{Muzalevskii:2020}, emitted from the target in the laboratory angular range between $8^{\circ}$ and $26^{\circ}$.
%The first one covered the laboratory angular range between $8^{\circ}$ and $26^{\circ}$ and allowed to identify and reconstruct low-energy particles, see Ref.\ \cite{Muzalevskii:2020}.
The front telescope covered angles $\leq9^{\circ}$ and was used to measure the high-energy particles (tritons with energy up to 160\,MeV), stopping them in the CsI(Tl) crystal.
Neutron detection was realized by the time-of-flight (ToF) stilbene modules \cite{Bezbakh:2018}.%, which provides reliable neutron-gamma separation and measure the particle energy.
