Protophobic Fifth-Force Interpretation of the Observed Anomaly in $^{8}\mathrm{Be}$ Nuclear Transitions

Protophobic Fifth-Force Interpretation of the Observed Anomaly in ${}^{8}{Be}$ Nuclear Transitions

Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, and Philip Tanedo

Phys. Rev. Lett. 117, 071803 – Published 11 August 2016

Abstract

Recently a $6.8 σ$ anomaly has been reported in the opening angle and invariant mass distributions of $e^{+} e^{-}$ pairs produced in ${}^{8}{Be}$ nuclear transitions. The data are explained by a 17 MeV vector gauge boson $X$ that is produced in the decay of an excited state to the ground state, ${}^{8}{Be}^{*} \to {}^{8}{Be} X$ , and then decays through $X \to e^{+} e^{-}$ . The $X$ boson mediates a fifth force with a characteristic range of 12 fm and has millicharged couplings to up and down quarks and electrons, and a proton coupling that is suppressed relative to neutrons. The protophobic $X$ boson may also alleviate the current $3.6 σ$ discrepancy between the predicted and measured values of the muon’s anomalous magnetic moment.

Received 3 May 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.071803

Physics Subject Headings (PhySH)

Electromagnetic transitions Extensions of gauge sector

Particles & FieldsNuclear Physics

Authors & Affiliations

Jonathan L. Feng¹, Bartosz Fornal¹, Iftah Galon¹, Susan Gardner^1,2, Jordan Smolinsky¹, Tim M. P. Tait¹, and Philip Tanedo¹

¹Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
²Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA