Fri·Mar 11, 2022Friday·March 11, 2022

1. 01*

   Neutrino-Flux Variability, Nuclear-Decay Variability, and Their Apparent Relationship

   Peter A. Sturrock🇺🇸

   Homestake, Gallex and GNO data reveal variability of the solar neutrino flux. Kamiokande records for 1996-2001 reveal oscillations at 9.43 and 12.6 yr${}^{-1}$, well within a range (6-16 yr${}^{-1}$) that, according to helioseismology, may be related to internal solar rotation. A nuclear-decay experiment at Brookhaven National Laboratory (for 1982-86) reveals strong oscillations at 11.2 and 13.2 yr${}^{-1}$. Similar oscillations are found in nuclear-decay measurements conducted by A. Parkhomov. By contrast, S. Pomme points out that nuclear-decay experiments at standards laboratories tend not to exhibit variability. The most extensive series of nuclear-decay measurements comes from an experiment initiated by G. Steinitz at the Geological Survey of Israel (2007-16), which recorded 340,000 radon-related measurements from each of 3 gamma detectors and 3 environmental sensors. Analysis of a subset of 85,000 hourly gamma measurements reveals a number of oscillation frequencies compatible with influences of internal solar rotation. There is no correlation between the gamma and environmental measurements. The solar internal magnetic field may lead to neutrino modulation by the RSFP (Resonant Spin-Flavor Precession) mechanism. A triplet of oscillations (7.43, 8.43 and 9.43 yr${}^{-1}$) may be attributed to an internal region (presumably the core) with a sidereal rotation rate of 8.43 yr${}^{-1}$ and a rotation axis roughly orthogonal to that of the photosphere. This suggests that the Sun had its origin in more than one stage of condensation of interplanetary material (one on top of another), which could lead to present-day layers with different metallicities, rotation rates and axes. The peak modulation occurs near local midnight in early June, suggestive of a role of cosmic neutrinos. These neutrinos could provide the mass attributed to dark matter for a neutrino mass of order 0.1 eV.

   ↳ astro-ph.SRhep-phnucl-exSpace Sci.Rev.(2022)·3 citations
2. 02*

   Complete theory of radiative corrections to $K_{\ell 3}$ decays and the $V_{us}$ update

   Chien-Yeah Seng🇩🇪 · Daniel Galviz🇩🇪 · Mikhail Gorchtein🇩🇪 · Ulf-G. Meißner🇩🇪

   We fill up the missing piece in our own re-analysis of the long-distance electromagnetic radiative corrections to semileptonic kaon decays by performing a rigorous study in the $K\to \pi {\mu }^{+}{\nu }_{\mu }(\gamma )$ channels. With appropriate experimental and lattice inputs, we achieve a precision level of $10^{-4}$ in these channels. This is comparable to our previous analysis in the $K\to \pi e^{+}{\nu }_e(\gamma )$ channels. With this new result, we present an updated global analysis to extract the Standard Model parameter $|V_{us}|$ from semileptonic kaon decays. We obtain $|V_{us}|=0.22308(55)$ and $0.22356(73)$, using the lattice average of the $K^0\to {\pi }^{-}$ transition form factor at $N_f=2+1+1$ and $N_f=2+1$, respectively.

   ↳ hep-phhep-exhep-lathep-th+1JHEP(2022)·48 citations
3. 03*

   Shape coexistence in Sr isotopes

   Esperanza Maya-Barbecho · José Enrique García-Ramos

   Sr isotopes are located in the mass region $A\approx 100$, where a very quick onset of nuclear deformation exists, being other notable examples of this area Yb, Zr, and Nb nuclei. The presence of the proton subshell closure $Z=40$ allows the existence of particle-hole excitations that produces low-lying intruder bands. Purpose: The goal of this work is the study of the nuclear structure of the even-even ${}^{92-102}$Sr isotopes through the accurate description of excitation energies, $B(E2)$ transition rates, nuclear radii and two-neutron separation energies. Method: The interacting boson model with configuration mixing will be the framework to calculate all the observables of the Sr isotopes. Only two types of configurations will be considered, namely, 0particle-0hole and 2particle-2hole excitations. The parameters of the model are determined using a least-squares procedure for the excitation energies and the $B(E2)$ transition rates. Results: For the whole chain of isotopes, the value of excitation energies, $B(E2)$'s, two-neutron separation energies, nuclear radii, and isotope shifts have been obtained, with a good agreement between theory and experiment. Also, a detailed analysis of the wave functions have been performed and, finally, the mean-field energy surfaces and the value of the nuclear deformation, $\beta$, have been obtained. Conclusions: The presence of low-lying intruder states in even-even Sr isotopes have been confirmed and its connection with the onset of deformation has been clarified. Lightest Sr isotopes present a spherical structure while the heaviest ones are clearly deformed. The rapid onset of deformation at neutron number $60$ is due to the crossing of the regular and intruder configurations and, moreover, both families of states present an increase of deformation with the neutron number.

   ↳ nucl-thnucl-exPRC(2022)·19 citations
4. 04*

   Asymmetric Nuclear Matter and Neutron Star Properties in Relativistic ab initio Theory in the Full Dirac Space

   Sibo Wang🇨🇳 · Hui Tong🇨🇳 · Qiang Zhao🇰🇷 · Chencan Wang🇨🇳 · Peter Ring🇩🇪 · Jie Meng🇨🇳

   The long-standing controversy about the isospin dependence of the effective Dirac mass in ab initio calculations of asymmetric nuclear matter is clarified by solving the relativistic Brueckner-Hartree-Fock equations in the full Dirac space. The symmetry energy and its slope parameter at the saturation density are $E_{\text{sym}}({\rho }_0)=33.1$ MeV and $L=65.2$ MeV, in agreement with empirical and experimental values. Further applications predict the neutron star radius $R_{1.4M_{\odot }}\approx 12$ km and the maximum mass of a neutron star $M_{\text{max}}\le 2.4M_{\odot }$.

   ↳ nucl-thnucl-exPRC(2022)·30 citations
5. 05*

   Questioning the 239Pu(n,2n)238Pu cross section shape above emission threshold

   O. Bouland🇫🇷 · V. Meot🇫🇷 · O. Roig🇫🇷

   In the light of the JEF(F) European project longstanding story according to the determination of the most exact shape of the 239Pu(n, 2n)238Pu reaction cross section and a recent measurement by Meot et al., this paper aims to shed another light on this topic by bringing new theoretical feedback. To achieve this goal, the AVXSF-LNG computer program has been upgraded to model second-chance reactions using its decay-probability module and, then chained to the TALYS-ECIS06 nuclear reaction system of codes. Present diligent calculation of the (n,2n) cross section over the energy range from the threshold to the onset of third-chance fission at about 12 MeV, suggests that current evaluations under-estimate the 239Pu(n,2n) cross section below 10 MeV; under-estimation of the order of 7% relatively to the JEFF-3.1 evaluation. On this ground, we propose an upward correction to the normalization of the measurement by Meot et al. Correction factor of about 1.24 with a maximum uncertainty on present fitted model estimated to 11.6%. Latter value is extracted from a sensitivity analysis of the calculation route to the level density model that is selected for the non-equilibrated residual nucleus and to alternative choices we can make in terms of neutron fission cross section measurement references for the 238Pu and 239Pu target nuclei.

   ↳ nucl-thnucl-exphysics.app-ph0 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.