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Neutron multiplicity in photonuclear reactions; invariance of classical electromagnetism; momentum transfer models in ion collisions; cosmic ray electromagnetic interactions; quadrupole excitations in nucleus-nucleus collisons and Y-89 interactions with relativistic nuclei; and the Weizsacker-Williams theory for nucleon emission via electromagnetic excitations in nucleus-nucleus collisions are discussed.
Photoneutron production is possible using an electron linear accelerator and a target capable of generating photonuclear reactions. A short pulse neutron source can be useful for neutron imaging dynamic experiments. This study is aimed at the feasibility of photoneutron production using a 20 MeV electron linear accelerator and tungsten and depleted uranium targets of various thicknesses. MCNP6 (Monte Carlo N-Particle) code will be used to develop a computational model to estimate total neutron yield, and this will be verified at the Idaho State University’s Accelerator Center. After verification of the neutron yield and energy spectra, an additional MCNP6 model will be developed to analyze the neutron imaging processes. This study will potentially prove it is possible to conduct multi-mode imaging experiments on the anticipated Scorpius electron linear accelerator at the Nevada National Security Sites.
Exclusive photoproduction of 𝐾 + Λ final states off a proton target has been an important component in the search for missing nucleon resonances and our understanding of the production of final states containing strange quarks. Polarization observables have been instrumental in this effort. The current work is an extension of previously published CLAS results on the beam-recoil transferred polarization observables 𝐶 𝑥 and 𝐶 𝑧 . Here, we extend the kinematic range up to invariant mass 𝑊 = 3.33 GeV from the previous limit of 𝑊 = 2.5 GeV with significantly improved statistical precision in the region of overlap. These data will provide for tighter constraints on the reaction models used to unravel the spectrum of nucleon resonances and their properties by not only improving the statistical precision of the data within the resonance region, but also constraining 𝑡-channel processes that dominate at higher 𝑊 but extend into the resonance region.
Photoproduction of charged pions pairs off protons is studied within the invariant masses of the final state hadrons from 1.6 to 2.4 GeV at the Thomas Jefferson National Accelerator Facility with the CLAS detector. The total and differential cross sections and spin-density matrix elements are presented for the isobars pρ 0 (770), Δ(1232) ++ π − , and Δ(1232) 0 π + . The data are included in the Bonn-Gatchina coupled-channel analysis and provide the information necessary to determine the branching fractions of Nρ(770) decays for most known N* and Δ* resonances. For the first time, the Nρ branching ratios are obtained here from an event-based likelihood to γp → π + π − p.
We report on the first measurement of J/ψ photoproduction from nuclei in the photon energy range of 7 to 10.8 GeV, extending above and below the photoproduction threshold in the free proton of ∼ 8.2 GeV. The experiment used a tagged photon beam incident on deuterium, helium, and carbon, and the GlueX detector at Jefferson Lab to measure the semi-inclusive A(γ, e + e − p) reaction with a dilepton invariant mass M(e + e − ) ∼ m J/ψ = 3.1 GeV. The incoherent J/ψ photoproduction cross sections in the measured nuclei are extracted as a function of the incident photon energy, momentum transfer, and proton reconstructed missing light-cone momentum fraction. Comparisons with theoretical predictions assuming a dipole form factor allow extracting a gluonic radius for bound protons of p $\sqrt4⟨r^2⟩$ = 0.85 ± 0.14 fm. The data also suggest an excess of the measured cross section for sub-threshold production and for interactions with high missing light-cone momentum fraction protons. The measured enhancement can be explained by modified gluon structure for high-virtuality bound-protons.
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We investigated the nuclear structure of 31 P near the proton threshold using nuclear resonance fluorescence (NRF) to refine the properties of key resonances in the 30 Si (𝑝,𝛾) 31 P reaction, which is critical for nucleosynthesis in stellar environments. Excitation energies and spin-parities were determined for several states, including two unobserved resonances at 𝐸 𝑟 = 18.7keV and 𝐸 𝑟 = 50.5keV. The angular correlation analysis enabled the first unambiguous determination of the orbital angular momentum transfer for these states. These results provide a significant update to the 30 Si (𝑝,𝛾) 31 P thermonuclear reaction rate, with direct implications for models of nucleosynthesis in globular clusters and other astrophysical sites. The revised rate is substantially lower than previous estimates at temperatures below 200 MK, affecting predictions for silicon isotopic abundances in stellar environments. Furthermore, our work demonstrates the power of NRF in constraining nuclear properties, and provides a framework for future studies of low-energy resonances relevant to astrophysical reaction rates.
We measure the spin-density matrix elements (SDMEs) for the photoproduction of 𝜙(1020) off of the proton in its decay to 𝐾$^{0}_{𝑆}$𝐾$^{0}_{𝐿}$, using 105 pb −1 of data collected with a linearly polarized photon beam using the GlueX experiment. The SDMEs are measured in nine bins of the squared four-momentum transfer 𝑡 in the range −𝑡=0.15−1.0 GeV 2 , providing the first measurement of their 𝑡 dependence for photon beam energies of 𝐸 𝛾 = 8.2−8.8 GeV. We confirm the dominance of Pomeron exchange in this region and put constraints on the contribution of other Regge exchanges. We also find that helicity amplitudes where the helicity of the photon and 𝜙(1020) differ by two units are negligible.
The quality of recent Short-Range Correlations/Color-Transparency (SRC/CT) Collaboration 𝐽/𝜓 photoproduction data off a 4 He target from Hall D at Jefferson Laboratory, combined with the feasibility of measuring the reaction close to the free-nucleon energy threshold, opens the door to using incoherent 𝐽/𝜓 photoproduction to explore a variety of interesting physics aspects. An example is the estimation of the 𝐽/𝜓 𝑝 scattering length |𝛼 𝐽/𝜓 𝑝 | on the bound proton, obtained using the vector meson dominance model. The new experiment E12–25–002, conducted by the SRC/CT Collaboration, was recently approved in Hall D with the GlueX spectrometer, which will significantly enhance the number of reconstructed 𝐽/𝜓 mesons. Using a plane-wave theoretical model to generate quasidata, we estimated that the experiment could achieve a result of |𝛼 𝐽/𝜓 𝑝 | = 3.08 ± 0.45 mfm. This value can be compared to an extraction based on the free proton data from the GlueX Collaboration, |𝛼 𝐽/𝜓 𝑝 | = 3.08 ± 0.55 mfm. A comparison between the two would provide an opportunity to evaluate the effects of medium modification in light nuclei.
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We demonstrate that the longitudinal single target-spin asymmetry in exclusive π 0 production in e p collisions can give access to the imaginary part of the gluon generalized transverse momentum distribution (GTMD) F 1 , 4 . Such a longitudinal spin asymmetry that results from the Coulomb-nuclear interference effect, leads to a characteristic azimuthal angular correlation of sin 2 ϕ , where ϕ is the azimuthal angle between the scattered lepton transverse momentum and the recoil proton’s transverse momentum. We also present a numerical estimate of the asymmetry for the kinematics accessible at EIC and EicC. Published by the American Physical Society 2024
The alphas sublibrary aims to describe nuclear reactions between incident alpha particles and different nuclei. For ENDF/B-VIII.1, the LLNL ECPL evaluation for 6Li, and the JENDL-based NNL evaluations of 9 Be and 16,17 O were adopted. Also, there were minor fixes done to 4 He.
The atomic relaxation sublibrary aims to describe atomic binding energies. For ENDF/B-VIII.1 we adopted the EPICS2023 EADL evaluations.
The decay sublibrary aims to describe all known spontaneous decays and branching ratios for all nuclei across the nuclide chart. ENDF/B-VIII.1 remains unchanged from ENDF/B-VIII.0 for the decay sublibrary.
The deuterons sublibrary aims to describe nuclear reactions between incident deuteron particles and different nuclei. For ENDF/B-VIII.1, we adopted additions and corrections to the ENDF/B-VIII.0 d+t file, as well as new LANL evaluation updates for 3 He and 6 Li.
The electrons sublibrary aims to describe electron-atomic cross section data, corresponding to the interaction between electrons and the different atoms. For ENDF/B-VIII.1 we adopted the EPICS2023 EEDL evaluations.
The Helium-3 (Helions) sublibrary aims to describe nuclear reactions between incident 3 He particles and different nuclei. For ENDF/B-VIII.1, we adopted a new 4He evaluation from the INDEN collaboration and the LLNL ECPL evaluation for 7 Li.