Dynamical evidence for a fifth force explanation of the ATOMKI nuclear anomalies

2020/06/30 by Jonathan L. Feng, Tim M. P. Tait, Christopher B. Verhaaren · 49 citations
Physics and Astronomy · #Anomaly (physics) #Boson #Dark Matter and Cosmic Phenomena #Excited state #Gauge boson #Gauge theory #Meson #Neutrino Physics Research #Nuclear physics #Parity (physics) #Particle physics #Particle physics theoretical and experimental studies #Physics #Physics beyond the Standard Model #Pseudoscalar #Pseudovector #Quantum mechanics #Scalar (mathematics) #Scalar boson #Vector boson #hep-ex #hep-ph #nucl-ex #nucl-th

paper · pdf · doi:10.1103/physrevd.102.036016

published in Physical review. D/Physical review. D. 102(3) (American Physical Society) · 32 pages, 6 figures; Corrected small typos and added references

openalex publication_date 2020/08/17 · arxiv created 2020/08/18 · arxiv updated 2020/08/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

Recent anomalies in ⁸Be and ⁴He nuclear decays can be explained by postulating a fifth force mediated by a new boson X. The distributions of both transitions are consistent with the same X mass, 17 MeV, providing kinematic evidence for a single new particle explanation. In this work, we examine whether the new results also provide dynamical evidence for a new particle explanation, that is, whether the observed decay rates of both anomalies can be described by a single hypothesis for the X boson's interactions. We consider the observed ⁸Be and ⁴He excited nuclei, as well as a ¹²C excited nucleus; together these span the possible J^P quantum numbers up to spin 1 for excited nuclei. For each transition, we determine whether scalar, pseudoscalar, vector, or axial vector X particles can mediate the decay, and we construct the leading operators in a nuclear physics effective field theory that describes them. Assuming parity conservation, the scalar case is excluded and the pseudoscalar case is highly disfavored. Remarkably, however, the protophobic vector gauge boson, first proposed to explain only the ⁸Be anomaly, also explains the ⁴He anomaly within experimental uncertainties. We predict signal rates for other closely related nuclear measurements, which, if confirmed by the ATOMKI group and others, would provide overwhelming evidence that a fifth force has been discovered.

Citations

• Dark-Matter Particles without Weak-Scale Masses or Weak Interactions
• Protophobic Fifth Force Interpretation of the Observed Anomaly in ⁸Be Nuclear Transitions
• Atomki Anomaly in Family-Dependent U(1)′ Extension of the Standard Model
• The AME2016 atomic mass evaluation (II). Tables, graphs and references
• New evidence supporting the existence of the hypothetic X17 particle

Cited by

• X17 discovery potential in the γN → e⁺ e^- N process at electron scattering facilities
• Combined Evidence for the X₁₇ Boson After PADME Results on Resonant Production in Positron Annihilation