Observation of Anomalous Internal Pair Creation in ⁸Be: A Possible Signature of a Light, Neutral Boson

2015/04/07 by A. J. Krasznahorkay, M. Csatlós, L. Csige +11 · 2 citations
Physics and Astronomy · #nucl-ex

paper · pdf · doi:10.1103/physrevlett.116.042501

published as Phys. Rev. Lett. 116, 042501 (2016) · 5 pages, 5 figures

arxiv created 2015/04/07 · arxiv updated 2016/02/03

Abstract

Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV state (J^π=1⁺, T=1) → ground state (J^π=0⁺, T=0) and the isoscalar magnetic dipole 18.15 MeV (J^π=1⁺, T=0) state → ground state transitions in ⁸Be. Significant deviation from the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of > 5σ. This observation might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of 16.70±0.35 (stat)± 0.5 (sys) MeV/c² and J^π= 1⁺ was created.

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