Related papers: An Update on the Hypothetical X17 Particle
Motivated by the recent observation of anomalous electron-positron angular correlations in the decay of the 18.15 MeV 1+ excited states in 8Be, we reexamine in detail the Standard Model expectations for these angular correlations. The 18.15…
We discuss a set of precision observables that can probe the existence of a light particle $X$ coupled to electrons in the mass range of 1-100 MeV. As a case study, we consider the recent excess of $e^+e^-$ final-state events at $\sqrt{s} =…
We present a hypothesis that the anomaly in the folding angle distribution of electron-positron pairs, emitted in the decay of the excited levels of nucleus $^{8}$Be and $^{4}$He can be related to the cluster structure of the decaying…
In this paper we report on a systematic search for a neutral boson in the mass range between 5 and 15 MeV/c$^{2}$ in the decay of highly excited nuclei. Its signature is found a deviation in the angular correlation of the $e^+e^-$ pairs…
Recent anomalies observed in $e^+e^-$ nuclear transitions of $^8 \textrm{Be}$, $^4 \textrm{He}$, and $^{12} \textrm{C}$ by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV, referred to as X17.…
Recent findings of an unexpected, narrow resonance in the $e^+e^-$ decay spectra of excited states of $^8$Be, $^4$He and $^{12}$C by the ATOMKI collaboration have received considerable experimental and theoretical attention, whereby a new,…
We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited Be-8 nucleus decays. Due to its coupling to electrons, the X could be produced in the…
The PADME experiment was originally designed to test dark matter theories predicting the existence of a ''Dark Sector'' composed of particles that interact with Standard Model ones exclusively through the exchange of a new, massive…
We show that the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS) at nuclear reactor experiments has significant sensitivity to the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly, wherein…
The recent ATOMKI experiments provided evidence pointing towards the existence of an X17 boson in the anomalous nuclear transitions of Beryllium-8, Helium-4, and Carbon-12. In this work, we consider X17 boson contributions to the previously…
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…
We present measurements of hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of $\sqrt{s_{NN}}=5.44$ and $5.02$ TeV, respectively, by the ALICE collaboration at…
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…
We report a direct search for a new gauge boson, $X$, with a mass of $17~\text{MeV}/c^2$, which could explain the anomalous excess of $e^+e^-$ pairs observed in the $^8\text{Be}$ nuclear transitions. The search is conducted in the…
In two recent reactions by Belle producing $D\bar D$ and $D\bar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such…
The dark matter and existence of new particles are now a possible explanation of several physics phenomena which evade the predictions of the Standard Model. In this context Axion-Like-Particles (ALP) with masses in the MeV to GeV range…
Two recent experimental observations at the ATOMKI Institute of the Hungarian Academy of Sciences (regarding the angular emission pattern of electron-positron pairs from nuclear transitions from excited states in 8Be and 4He) indicate the…
Recently, it has been proposed that the observed anomaly in the time distribution of neutrino induced reactions, reported by the KARMEN collaboration, can be interpreted as a signal from an exotic muon decay branch mu+ to e+ X. It has been…
The energy and angular dependencies of double differential cross sections d^2sigma/dOmegadE were measured for p,d,t,^{3,4,6}He,^{6,7,8}Li,{7,9,10}Be, and ^{10,11,12}B produced in collisions of 1.2, 1.9, and 2.5 GeV protons with an Al…
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…