Abstract
An experiment is proposed aiming at the unambiguous detection of mass A = 2 neutral particles via elastic scattering and neutron exchange reactions on protons in a plastic scintillating fibre detector. Di-neutrons would be produced in ordinary π − absorption at rest on 3He together with tagging protons. The basic advantages of the proposed process are the strict collinearity and opposite, and constant momenta of hypothetical di-neutrons and recoiling particles in the LAB reference frame. Moreover, the detection cross sections (2 n + p → p + 2 n; 2 n + p → d + n) are calculable with three-nucleon codes based on 1 a nn dependent nn interactions.
Highlights
A recent announcement of a discovery of bound di-neutrons existing in neutron halo nuclei [1] revived interest to these hypothetical, electrically neutral light nuclei
The phenomenon is very similar—if not identical—to the so called nn final state interaction peak observed frequently in many nuclear reactions in a specific kinematical configuration where the neutron pair with low relative momentum is emitted back-to-back with the recoiling system
Distinguishing between di-neutron clustering in nuclei and nn final state interaction (nn-FSI) is not an easy task as the effective interactions in a model space consisting of halo neutrons and a core are complex and poorly known
Summary
A recent announcement of a discovery of bound di-neutrons existing in neutron halo nuclei [1] revived interest to these hypothetical, electrically neutral light nuclei. The sign of 1ann, which is decisive for the existence or non-existence of a bound state, must be established from coherent neutron-neutron scattering Since such an experiment has not been done yet, the negative sign of 1ann is motivated mainly by the lack of observation of bound multi-neutron systems, consistency in the description of the experimental data by the model nucleon-nucleon forces and isospin conservation in strong interactions. Distinguishing between di-neutron clustering in nuclei and nn-FSI is not an easy task as the effective interactions in a model space consisting of halo neutrons and a core are complex and poorly known. This fact was pointed out in Ref. These objects must be stable in vacuum with respect to strong interactions and can decay only via weak interactions
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