X17 boson and the H2(p,e+e−)He3 and H2(n,e+e−)H3 processes: A theoretical analysis

The present work deals with the 𝑒+−𝑒− pair production in the 2 H ⁡(𝑝,𝑒+⁢𝑒−)⁢ 3 He and 2 H ⁡(𝑛,𝑒+⁢𝑒−)⁢ 3 H processes, in order to make evident possible effects due to the exchange of a hypothetical low-mass boson, the so-called X17. These processes are studied for energies of the incident beams in the range 18–30 MeV, in order to have a sufficient energy to produce such a boson, whose mass is estimated to be around 17 MeV. We first analyze them as purely electromagnetic processes, in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory (𝜒⁢EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross sections for such processes. We consider several possibilities: that this boson is either a scalar, pseudoscalar, vector, or axial particle. The main aim of the study is to exploit the specular structure of the 3 He and 3 H nuclei to investigate the isospin dependency of the X17-nucleon interaction, as the alleged “protophobicity.”