The X17 boson and the ${}^3$H$(p,e^{+}{e}^{-}{)}^4$He and ${}^3$He$(n,e^{+}{e}^{-}{)}^4$He processes: a theoretical analysis

Abstract

The present work deals with $e^{+}$-$e^{-}$ pair production in the four-nucleon system. We first analyze the process as a purely electromagnetic one 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 ($\chi$EFT). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross section for such a process. We consider several possibilities, that this boson is either a scalar, pseudoscalar, vector, or axial particle. The ab initio calculations use exact hyperspherical-harmonics methods to describe the bound state and low-energy spectrum of the $A$=$4$ continuum, and fully account for initial state interaction effects in the $3+1$ clusters. While electromagnetic interactions are treated to high orders in the chiral expansion, the interactions of the hypothetical boson with nucleons are modeled in leading-order $\chi$EFT (albeit, in some instances, selected subleading contributions are also accounted for). We also provide an overview of possible future experiments probing pair production in the $A$=$4$ system at a number of candidate facilities.facilities.

32 pages, 17 figures. Corrected version, having fixed a problem with a phase in the multipolar expansions. Only Figs. 4 and 10 change significantly, the rest only marginally. The conclusions are unchanged. We include also a number of improvements: 1) better wave functions, 2) the isoscalar pseudoscalar case, and 3) the comparison with the new ATOMKI data (see new Fig. 17)

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Cited by in corpus (14)

• New anomaly observed in ${}^{12}$C supports the existence and the vector character of the hypothetical X17 boson
• QED Meson Description of the X17 and Other Anomalous Particles
• Resonant search for the X17 boson at PADME
• Solar fusion III: New data and theory for hydrogen-burning stars
• Neutrino Constraints and the ATOMKI X17 Anomaly
• Status of the X17 search in Montreal
• On the Atomki nuclear anomaly after the MEG-II result
• X17 discovery potential in the $\gamma N\to e^{+}{e}^{-}N$ process at electron scattering facilities
• Ab initio investigation of the ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be process and the X17 boson
• Perspectives on few-body cluster structures in exotic nuclei
• On the question of quark confinement in the Abelian U(1) QED gauge interaction
• Dynamics of quarks and gauge fields in the lowest-energy states in QCD and QED
• QED meson description of the anomalous particles at ~17 and ~38 MeV
• Contributions to $Z^0$ decays from a X17 extension of the Standard Model