Particle physics models for the 17 MeV anomaly in beryllium nuclear decays

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

Research output: Contribution to journalArticlepeer-review

124 Scopus citations


The 6.8σ anomaly in excited Be8 nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in Be8 decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited Be8 decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the Be8 anomaly. In the first model, the new force carrier is a U(1)B gauge boson that kinetically mixes with the photon; in the second model, it is a U(1)B-L gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings ∼0.001 that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.

Original languageEnglish
Article number035017
JournalPhysical Review D
Issue number3
StatePublished - Feb 16 2017

Bibliographical note

Funding Information:
We thank Phil Barbeau, John Beacom, Roy Holt, Yoni Kahn, Attila J. Krasznahorkay, Saori Pastore, Tilman Plehn, Mauro Raggi, Alan Robinson, Martin Savage, Paolo Valente, and Robert Wiringa for helpful correspondence. J.L.F., B.F., I.G., J.S., T.M.P.T., and P.T. are supported in part by NSF Grants No.PHY-1316792 and No.PHY-1620638. The work of S.G. is supported in part by the DOE Office of Nuclear Physics under Contract No.DE-FG02-96ER40989. The work of J.L.F. is supported in part by a Guggenheim Foundation grant and in part by Simons Investigator Award No.376204 and was performed in part at the Aspen Center for Physics, which is supported by NSF Grant No.PHY-1066293.

Publisher Copyright:
© 2017 American Physical Society.

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


Dive into the research topics of 'Particle physics models for the 17 MeV anomaly in beryllium nuclear decays'. Together they form a unique fingerprint.

Cite this