Experimental search for the bound state singlet deuteron in the radiative n-p capture

TL;DR

This study experimentally searched for a hypothesized bound singlet deuteron state near the disintegration threshold by detecting gamma-ray cascades after neutron capture, setting an upper limit on its production cross section.

Contribution

First experimental search for the bound singlet deuteron in neutron-proton capture, providing upper limits on its production cross section near the threshold.

Findings

No evidence of the singlet deuteron was observed.

An upper limit of 2 microbarns was established for its production cross section.

The bound energy range investigated was 10-125 keV.

Abstract

We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The predicted energy of this metastable level is in vicinity of the deuteron disintegration threshold. This state should manifest itself in two-photon transition following thermal neutron capture by protons. The experiment consists in the search for the second gamma-ray in the cascade through a high statistics measurement of $\gamma$-ray spectra after cold neutron capture by hydrogen nuclei. The upper limit $2\mu$b (2$\sigma$ level) is obtained for the cross section of the singlet deuteron production with the bound energy in the range 10-125 keV.