Thu·Sep 30, 2021Thursday·September 30, 2021

1. 01*

   Energy Dependence of Prompt Fission Neutron Multiplicity in the ${}^{239}$Pu($n,f$) Reaction

   P. Marini🇫🇷 · J. Taieb🇫🇷 · D. Neudecker🇺🇸 · G. Bélier🇫🇷 · A. Chatillon🇫🇷 · D. Etasse🇫🇷 · B. Laurent🇫🇷 · P. Morfouace🇫🇷 · B. Morillon🇫🇷 · M. Devlin🇺🇸 · J. A. Gomez🇺🇸 · R. C. Haight🇺🇸 · K. J. Kelly🇺🇸 · J. M. O'Donnell🇺🇸

   Accurate multiplicities of prompt fission neutrons emitted in neutron-induced fission on a large energy range are essential for fundamental and applied nuclear physics. Measuring them to high precision for radioactive fissioning nuclides remains, however, an experimental challenge. In this work, the average prompt-neutron multiplicity emitted in the 239Pu(n,f) reaction was extracted as a function of the incident-neutron energy, over the range 1-700~MeV, with a novel technique, which allowed to minimize and correct for the main sources of bias and thus achieve unprecedented precision. At low energies, our data validate for the first time the ENDF/B-VIII.0 nuclear data evaluation with an independent measurement and reduce the evaluated uncertainty by up to $60\%$. This work opens up the possibility of precisely measuring prompt fission neutron multiplicities on highly radioactive nuclei relevant for an essential component of energy production world-wide.

   nucl-exPLB(2022)·11 citations
2. 02*

   The Status and Future of Direct Nuclear Reaction Measurements for Stellar Burning

   M. Aliotta · R. Buompane🇮🇹 · M. Couder · A. Couture🇺🇸 · R.J. deBoer · A. Formicola🇮🇹 · L. Gialanella🇮🇹 · J. Glorius · G. Imbriani🇮🇹 · M. Junker🇮🇹 · C. Langer🇺🇸 · A. Lennarz🇨🇦 and 13 other authors

   The study of stellar burning began just over 100 years ago. Nonetheless, we do not yet have a detailed picture of the nucleosynthesis within stars and how nucleosynthesis impacts stellar structure and the remnants of stellar evolution. Achieving this understanding will require precise direct measurements of the nuclear reactions involved. This report summarizes the status of direct measurements for stellar burning, focusing on developments of the last couple of decades, and offering a prospectus of near-future developments.

   nucl-exastro-ph.SRJ.Phys.G(2022)·21 citations
3. 03*

   Search for a bound di-neutron by comparing ${}^3$He(e,e'p)d and ${}^3$H(e,e'p)X measurements

   D. Nguyen🇺🇸 · C. Neuburger🇮🇱 · R. Cruz-Torres🇺🇸 · A. Schmidt🇺🇸 · D.W. Higinbotham🇺🇸 · J. Kahlbow🇺🇸 · P. Monaghan🇺🇸 · E. Piasetzky🇮🇱 · O. Hen🇺🇸

   We report on a search for a bound di-neutron by comparing electron-induced proton-knockout $(e,e^{\prime }p)$ measurements from Helium-3 (${}^3$He) and Tritium (${}^3$H). The measurements were performed at Jefferson Lab Hall A with a 4.326 GeV electron beam, and kinematics of large momentum transfer $Q^2\approx 1.9$ (GeV/$c$)${}^2$ and $x_B>1$, to minimize contributions from non quasi-elastic (QE) reaction mechanisms. Analyzing the measured ${}^3$He missing mass ($M_{miss}$) and missing energy ($E_{miss}$) distributions, we can distinguish the two-body break-up reaction, in which the residual proton-neutron system remains bound as a deuteron. In the ${}^3$H mirror case, under the exact same kinematic conditions, we do not identify a signature for a bound di-neutron with similar binding energy to that of the deuteron. We calculate exclusion limits as a function of the di-neutron binding energy and find that, for binding equivalent to the deuteron, the two-body break-up cross section on ${}^3$H is less than 0.9% of that on ${}^3$He in the measured kinematics at the 95% confidence level.

   nucl-exnucl-thPLB(2022)·6 citations
4. 04*

   Nuclear fusion catalyzed by doubly charged scalars: Implications for energy production

   Evgeny Akhmedov (MPIK Heidelberg)🇩🇪

   A number of popular extensions of the Standard Model of particle physics predict the existence of doubly charged scalar particles $X^{\pm \pm }$. Such particles may be long-lived or even stable. If exist, $X^{--}$ could form atomic bound states with light nuclei and catalyze their fusion by essentially eliminating the Coulomb barrier between them. Such an $X$-catalyzed fusion ($X$CF) process does not require high temperatures or pressure and may have important applications for energy production. A similar process of muon-catalyzed fusion ($\mu$CF) has been shown not to be a viable source of energy because of the sticking of negative muons to helium nuclei produced in the fusion of hydrogen isotopes, which stops the catalytic process. We analyze $X$CF in deuterium environments and show that the $X$-particles can only stick to ${}^6$Li nuclei, which are produced in the third-stage reactions downstream in the catalytic cycle. The corresponding sticking probability is very low, and, before getting bound to ${}^6$Li, each $X$-particle can catalyze $\sim 3.5\cdot 10^9$ fusion cycles, producing $\sim 7\cdot 10^4$ TeV of energy. We also discuss the ways of reactivating the $X$-particles from the Coulomb-bound (${}^6\mathrm{Li}X$) states, which would allow re-using them in $X$CF reactions.

   ↳ hep-phastro-ph.SRhep-exnucl-ex+1PRD(2022)·4 citations
5. 05*

   Systematical studies of the E1 photon strength functions combining Skyrme-HFB+QRPA model and experimental giant dipole resonance properties

   Y. Xu🇷🇴 · S. Goriely🇧🇪 · E. Khan🇫🇷

   Valuable theoretical predictions of nuclear dipole excitations in the whole nuclear chart are of great interest for different applications, including in particular nuclear astrophysics. We present here the systematic study of the electric dipole (E1) photon strength functions (PSFs) combining the microscopic Hartree-Fock-Bogoliubov plus Quasiparticle Random Phase Approximation (HFB+QRPA) model and the parametrizations constrained by the available experimental giant dipole resonance (GDR) data. For about 10000 nuclei with 8<Z<124 lying between the proton and the neutron drip-lines on nuclear chart, the particle-hole strength distributions are computed using the HFB+QRPA model under the assumption of spherical symmetry and making use of the BSk27 Skyrme effective interaction derived from the most accurate HFB mass model (HFB-27) so far achieved. Large-scale calculations of the BSk27+QRPA E1 PSFs are performed in the framework of a specific folding procedure, in which three phenomenological improvements are considered. First, two interference factors are introduced and adjusted to reproduce at best the available experimental GDR data. Second, an empirical expression accounting for the deformation effect is applied to describe the peak splitting of the strength function. Third, the width of the strength function is corrected by a temperature-dependent term, which effectively increases the de-excitation photon strength function at low-energy. The E1 PSFs as well as the extracted GDR peaks and widths are compared with available experimental data. A relatively good agreement with data indicates the reliability of the calculations. Eventually, the astrophysical (n,g) rates for all the 10000 nuclei with 8<Z<124 are estimated using the present E1 PSFs. The resulting reaction rates are compared with previous BSk7+QRPA results and Gogny-HFB+QRPA predictions based on the D1M interaction.

   ↳ nucl-thastro-ph.SRnucl-exPRC(2021)·18 citations
6. 06*

   Generalization of the Maier-Leibniz Doppler-Shift Method for Gamma-Ray Correlations in Fission

   Stefano Marin🇺🇸 · M. Stephan Okar🇺🇸 · Shaun D. Clarke🇺🇸 · Sara A. Pozzi🇮🇹

   The Maier-Leibniz Doppler-Shift technique is the most popular and accurate technique used in fission experiments to separate the yield of gamma rays from each of the two fission fragments. The technique exploits the aberration, i.e., the change in the angular distribution, of gamma rays emitted by a moving source. By measuring the speed and direction of the source with a conventional detector, as well as the yield of gamma rays at several angles from the direction of motion, the technique can be used to determine the mean multiplicities of gamma rays from each fragment. We show in this work that it is possible to extend the technique to also measure second moments of the gamma ray radiation from each fragment. In particular, given the current interest in fragment correlations in fission, we show that the covariance of the emission between the two fragments can be inferred. Experimental limitations and convergence of the new technique are discussed.

   ↳ physics.ins-detnucl-ex0 citations
7. 07*

   Enhancement of baryon-to-meson ratios around jets as a signature of medium response

   Ao Luo🇨🇳 · Ya-Xian Mao🇨🇳 · Guang-You Qin🇨🇳 · En-Ke Wang🇨🇳 · Han-Zhong Zhang🇨🇳

   We present a unique signal of jet-induced medium excitations: the enhancement of baryon-to-meson ratios around the quenched jets.To illustrate this, we study jet-particle correlations and the distributions of jet-induced identified particles with respect to the jet direction in Pb+Pb collisions at the LHC via a multi-phase transport model.We find a strong enhancement of baryon-to-meson ratios for associated particles at intermediate transverse momentum around the triggered jets in Pb+Pb collisions relative to p+p collisions, due to the coalescence of jet-excited medium partons.Since the lost energy from jets can diffuse to large angles, such baryon-to-meson-ratio enhancement is more pronounced for larger relative distance from the jet axis.We argue that the experimental confirmation of the enhancement of jet-induced baryon-to-meson ratios around the jets will provide an unambiguous evidence for the medium response to jet quenching in heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thPLB(2023)·35 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.