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

by Attila Krasznahorkay (CERN)

Thursday 16 Mar 2017, 13:00 → 14:00 Europe/Brussels

E/3rd floor-E.349 - Seminar room (E.349) (Marc de Hemptinne (chemin du Cyclotron, 2, Louvain-la-Neuve))

Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV state (Jπ=1+, T=1) → ground state (Jπ=0+, T=0) and the isoscalar magnetic dipole 18.15 MeV (Jπ=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 Jπ=1+ was created.

Slides anomaly_in_8Be.pdf