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Recently a 6.8$\sigma$ anomaly has been reported in the opening angle and invariant mass distributions of $e^+ e^-$ pairs produced in $^8\text{Be}$ nuclear transitions. The data are explained by a 17 MeV vector gauge boson $X$ that is…
Recent anomalies in $^8$Be and $^4$He nuclear decays can be explained by postulating a fifth force mediated by a new boson $X$. The distributions of both transitions are consistent with the same $X$ mass, 17 MeV, providing kinematic…
Using the $e^+e^-$ pair spectrometer at the 5 MV Van de Graaff accelerator at the Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Krasznahorkay et al. have claimed a 6.8$\sigma$ excess at high $e^+e^-$ opening angles…
New hidden particles could potentially be emitted and discovered in rare nuclear transitions. In this work we investigate the production of hidden vector bosons with primarily axial couplings to light quarks in nuclear transitions, and we…
The 6.8$\sigma$ anomaly in excited 8Be 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…
In view of the latest experimental results recently released by the ATOMKI collaboration, we critically re-examine the possible theoretical interpretation of the observed anomalies in terms of a new BSM boson $X$ with mass $\sim17\;$MeV. To…
Recently the experimentalists in [PRL 116, 042501 (2016)] announced observing an unexpected enhancement of the electron-positron pair production signal in one of the Beryllium-8 nuclear transitions. The following studies have been focused…
An anomaly observed recently in the $^8$Be nuclear transition by the Atomki collaboration hints at a weakly-coupled, light new gauge boson with a mass of about $17$ MeV. In this paper, we propose that this new gauge boson comes from a…
Recently, a peak in the light fermion pair spectrum at invariant q^2 approximately equal to 16.7 Me^2. has been observed in the bombardment of Li-7 by protons. This peak has been interpreted in terms of a protophobic interaction of fermions…
In recent electron-positron angular correlation measurements the observed significant enhancements relative to the internal pair creation at large angles was interpreted as indication of the creation of $J^{\pi }=1^{+}$ boson called X17…
The Atomki anomaly puts forward the hypothesis of an $X(17)$ particle to explain the observation. Utilizing experimental data from the Atomki experiments, measurements of the electron's anomalous magnetic moment, beam dump experiments, the…
A $6.8\,\sigma$ anomaly has been reported in the opening angle and invariant mass distributions of $e^+e^-$ pairs produced in ${^8Be}$ nuclear transitions. It has been shown that a protophobic fifth force mediated by a $17\,\textrm{MeV}$…
The observation of a protophobic 16.7 MeV vector boson has been reported by a $^8$Be nuclear transition experiment. Such a new particle could mediate between the Standard Model and a dark sector, which includes the dark matter. In this…
Motivated by a simultaneous explanation of the apparent discrepancies in the light charged lepton anomalous magnetic dipole moments, and the anomalous internal pair creation in $^8$Be nuclear transitions, we explore a simple New Physics…
The anomalies recently reported in lepton pair transitions of $^8$Be$^*$ and $^4$He nuclei may be attributed to the existence of a feebly interacting light vector boson $X17$. We study the effects of this hypothetical particle in the…
In recent years, the ATOMKI collaboration has performed a series of measurements of excited nuclei, observing a resonant excess of electron-positron pairs at large opening angles compared to the Standard Model prediction. The excess has…
The anomaly found in the excited $^8\text{Be}$ nuclear transition to its ground state is attributed to a spin-1 gauge boson $X(16.7)$. To hunt for this boson, we propose two traps: $e^+e^-\to X\gamma$ and $J/\psi\to X\gamma$, both following…
We discuss the current status of the anomaly in beryllium-8 nuclear transitions recently reported in the angular distribution of internal conversion electron-positron pairs. We present a phenomenological analysis of the signal and review…
The Atomki collaboration has reported that unexpected excesses have been observed in the rare decays of Beryllium nucleus. It is claimed that such excesses can suggest the existence of a new boson, called $X$, with the mass of about $17$…
We propose a direct search for the X17 particle, which was conjectured to explain the ATOMKI $^8$Be and $^4$He anomalies, through the dilepton photoproduction process on a nucleon in the photon energy range below or around the pion…