Internal pair creation anomalies and the X-boson

by Tommaso Marchi (INFN - LNL)



A laboratory experiment in Hungary has recently spotted an anomaly in radioactive decays that was interpreted as the signature of a previously unknown fifth fundamental force of nature. In a recent publication [Phys Rev Lett 116 042501 (2016)], the measurement of electron-positron angular correlations for the isovector magnetic dipole 17.6 MeV (Jπ =1+, T=1) state → ground state (Jπ=0+, T=0) and the isoscalar magnetic dipole 18.15 MeV (Jπ=1+, T=0) state → ground state transitions in 8Be are reported. A. J. Krasznahorkay and collaborators state that: “significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of > 5σ”. In the same paper, the result is interpreted as: “possibly due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of 16.70±0.35(stat)±0.5(syst) MeV/c2 and Jπ=1+ was created”. The same group has later reported compatible findings in the decay of 4He excited through the p+3H reaction and strong support in favour of the boson scenario is provided by theoretical studies.
If confirmed, such result and the relative interpretation would mean the discovery of a new fundamental manifestation of Nature’s forces. In the seminar I will briefly summarize the X-boson saga and describe the current efforts for providing an independent replica of the experiments with improved sensitivity.