A new light particle is being born

Abstract

A few years ago we observed anomalous electron-positron angular correlations for the 18.15 MeV M1 transition of 8Be. This was interpreted as the creation and decay of an intermediate bosonic particle with a mass of m 0 c 2=16.70±0.35(stat )±0.5(sys) MeV, which is now called X17. The possible relation of the X17 boson to the dark matter problem triggered an enormous interest in the wider physics community. We also observed a similar anomaly in 4He, which could be described also by the creation and subsequent decay of the same X17 particle. Very recently, the 11B proton capture reaction was used for exciting the 17.2 MeV broad (Γ=1.15 MeV) resonance in 12C and studying their internal pair creation decay. Anomalies were observed in the angular correlation of the electron-positron pairs, which together with the 8Be and 4He data provides kinematic evidence for the X17 particle and supports their vector boson and fifth force explanation.

QED Meson Description of the Anomalous Particles at ∼17 and ∼38 MeV

“…In ATOMKI and HUS experiments, proton beams at a laboratory energy of 0.5 to 4.0 MeV were used to fuse a proton with 3 H, 7 Li, and 11 B target nuclei to form excited states of 4 He, 8 Be, and 12 C, respectively [37][38][39][40][41][42][43][44][45]47]. The product nuclei are alpha-conjugate nuclei, and the reactions take place at energies below or just above the Coulomb barrier.…”

“…The mass of a QED meson can be obtained by measuring the invariant mass of its decay products. Since 2016, the ATOMKI Collaboration has been observing the occurrence of a neutral boson, the hypothetical X17, with a mass of about 17 MeV, by studying the e + e − spectrum in the de-excitation of the excited alpha-conjugate nuclei 4 He * , 8 Be * , 12 C * at various energies in low-energy proton fusion experiments [37,39,41,44]. A summary and update of the ATOMKI results has been presented [43,44], and the confirmation of the ATOMKI data for the p + 7 Be reaction by Hanoi University of Science has been reported [45].…”

“…Since 2016, the ATOMKI Collaboration has been observing the occurrence of a neutral boson, the hypothetical X17, with a mass of about 17 MeV, by studying the e + e − spectrum in the de-excitation of the excited alpha-conjugate nuclei 4 He * , 8 Be * , 12 C * at various energies in low-energy proton fusion experiments [37,39,41,44]. A summary and update of the ATOMKI results has been presented [43,44], and the confirmation of the ATOMKI data for the p + 7 Be reaction by Hanoi University of Science has been reported [45]. Many distribution functions of the opening angle θ e + e − between e + and e − have been successfully described as the production of the X17 particle with an invariant mass of about 17 MeV.…”

“…23 MeV I(J π )=1(1 − ) excited 12 C state to the 12 C ground state [41]. Updates of the ATOMKI measurements on the hypothetical X17 particle have also been presented [42][43][44]. In a recent measurement in the decay of the 8 Be 18.15 MeV state to the 8 Be ground state in the proton fusion on 7 Li, the Hanoi University of Science reported the observation of a significant structure, which indicates a hypothetical neutral boson with a mass of about 16.7 MeV decaying into e + e − , in support of the earlier ATOMKI observation [45].…”

“…The proposed models include the QED meson [24][25][26][27][28][29][30][31][32], the axion [49], the fifth force of Nature [50], a dark photon [53], new physics particles [54], the Framed Standard Model [55][56][57][58], Higgs doublet [59], a 12-quark state [62], a light pseudoscalar [63], and dressed QED radiation [71]. The experimental confirmation of the hypothetical X17 particle is being actively pursued by many laboratories [42], including ATOMKI [43,44], HUS [45], Dubna [72], New JEDI [73], STAR [74], MEGII [75,76], ATLAS [77,78], CTU Prague [79,80], NTOF [81], NA64 [82], INFN-Rome [83], NA48 [84], Mu3e [85], MAGIX/DarkMESA [86], JLAB PAC50 [87,88], PADME [89,90], DarkLight [91,92], LUXE…”