Ab initio investigation of the ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be process and the X17 boson

Abstract

Observations of anomalies in the electron-positron angular correlations in high-energy decays in ${}^4$He, ${}^8$Be, and ${}^{12}$C have been reported recently by the ATOMKI collaboration. These could be explained by the creation and subsequent decay of a new boson with a mass of $\sim 17$ MeV. Theoretical understanding of pair creation in the proton capture reactions used in these experiments is important for the interpretation of the anomalies. We apply the ab initio No-Core Shell Model with Continuum (NCSMC) to the proton capture on ${}^7$Li. The NCSMC describes both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. We investigate the structure of ${}^8$Be, the $p{+}^7$Li elastic scattering, the ${}^7$Li($p,\gamma$)${}^8$Be cross section and the internal pair creation ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be. We discuss the impact of a proper treatment of the initial scattering state on the electron-positron angular correlation spectrum and compare our results to available ATOMKI data sets. Finally, we calculate ${}^7$Li($p,X$)${}^8$Be cross sections for several proposed models of the hypothetical X17 particle.

arXiv comment32 pages, 13 figures. Matches more closely the published version

References in corpus (39)

• Accurate Charge-Dependent Nucleon-Nucleon Potential at Fourth Order of Chiral Perturbation Theory
• Properties of ${}^{12}$C in the {\it ab initio} nuclear shell-model
• Similarity Renormalization Group for Nucleon-Nucleon Interactions
• The R-matrix theory
• Observation of Anomalous Internal Pair Creation in ${}^8$Be: A Possible Signature of a Light, Neutral Boson
• Recent developments in no-core shell-model calculations
• Discrepancy between experimental and theoretical $\beta$-decay rates resolved from first principles
• Local three-nucleon interaction from chiral effective field theory
• Evolution of Nuclear Many-Body Forces with the Similarity Renormalization Group
• Protophobic Fifth Force Interpretation of the Observed Anomaly in ${}^8$Be Nuclear Transitions
• ALPtraum: ALP production in proton beam dump experiments
• Unified ab initio approaches to nuclear structure and reactions
• Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear Decays
• Novel chiral Hamiltonian and observables in light and medium-mass nuclei
• Unified ab initio approach to bound and unbound states: no-core shell model with continuum and its application to 7He
• Ab initio description of the exotic unbound 7He nucleus
• Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into $e^{+}{e}^{-}$ pairs
• Can Ab Initio Theory Explain the Phenomenon of Parity Inversion in ${}^{11}$Be?
• A new anomaly observed in ${}^4$He supports the existence of the hypothetical X17 particle
• ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ and ${}^3\mathrm{H}(\alpha ,\gamma ){}^7\mathrm{Li}$ astrophysical $S$ factors from the no-core shell model with continuum
• Unitary Correlation Operator Method and Similarity Renormalization Group: Connections and Differences
• Light Axial Vectors, Nuclear Transitions, and the ${}^8$Be Anomaly
• New anomaly observed in ${}^{12}$C supports the existence and the vector character of the hypothetical X17 boson
• Can nuclear physics explain the anomaly observed in the internal pair production in the Beryllium-8 nucleus?
• Dynamical Evidence For a Fifth Force Explanation of the ATOMKI Nuclear Anomalies
• QED Meson Description of the X17 and Other Anomalous Particles
• Can a protophobic vector boson explain the ATOMKI anomaly?
• Ab initio prediction of the ${}^4\mathrm{He}(d,\gamma ){}^6\mathrm{Li}$ big bang radiative capture
• Signals of the QCD axion with mass of 17 MeV/c^2: nuclear transitions and light meson decays
• The X17 boson and the ${}^3$H$(p,e^{+}{e}^{-}{)}^4$He and ${}^3$He$(n,e^{+}{e}^{-}{)}^4$He processes: a theoretical analysis
• Resonant search for the X17 boson at PADME
• Further search for a neutral boson with a mass around 9 MeV/c2
• An updated view on the ATOMKI nuclear anomalies
• Microscopic investigation of the ${}^8$Li($n,\gamma$)${}^9$Li reaction
• Neutrino Constraints and the ATOMKI X17 Anomaly
• The Angular Correlations in the $e^{+}{e}^{-}$ Decay of Excited States in 8Be
• Status of the X17 search in Montreal
• X17 discovery potential in the $\gamma N\to e^{+}{e}^{-}N$ process at electron scattering facilities
• QED meson description of the anomalous particles at ~17 and ~38 MeV

Cited by in corpus (3)

• On the Atomki nuclear anomaly after the MEG-II result
• Applications of the Modified Hulthén-Kohn Method for Bound and Scattering States
• Contributions to $Z^0$ decays from a X17 extension of the Standard Model