Recently, a peak in the light fermion pair spectrum at invariant q)2 ≈ (16.7MeV)2 has been observed in the bombardment of 7Li by protons. This peak has been interpreted in terms of a protophobic interaction of fermions with a gauge boson (X boson) of invariant mass ≈16.7MeV which couples mainly to neutrons. High-precision atomic physics experiments aimed at observing the protophobic interaction need to separate the X boson effect from the nuclear-size effect, which is a problem because of the short range of the interaction (11.8 fm), which is commensurate with a "nuclear halo." Here we analyze the X boson in terms of its consequences for both electronic atoms as well as muonic hydrogen and deuterium. We find that the most promising atomic systems where the X boson has an appreciable effect, distinguishable from a finite-nuclear-size effect, are muonic atoms of low and intermediate nuclear charge numbers.




Support by the National Science Foundation (Grants No. PHY-1403973 and No. PHY-1710856) is also gratefully acknowledged. A Missouri Research Board grant also assisted the completion of this research, and the work was supported by a Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences.

Keywords and Phrases

Atoms, Atomic system; Gauge bosons; High-precision; Invariant mass; Muonic hydrogen; Nuclear charge numbers; Nuclear sizes; Physics experiments, Bosons

International Standard Serial Number (ISSN)

2469-9926; 2469-9934

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2018 American Physical Society (APS), All rights reserved.

Publication Date

01 Apr 2018

Included in

Physics Commons