Fri·Jul 1, 2022Friday·July 1, 2022

1. 01*

   Investigating nuclear structure near $N=32$ and $N=34$: Precision mass measurements of neutron-rich Ca, Ti and V isotopes

   W. S. Porter🇨🇦 · E. Dunling🇨🇦 · E. Leistenschneider🇺🇸 · J. Bergmann🇩🇪 · G. Bollen🇺🇸 · T. Dickel🇩🇪 · K. A. Dietrich🇨🇦 · A. Hamaker🇺🇸 · Z. Hockenbery🇨🇦 · C. Izzo🇨🇦 · A. Jacobs🇨🇦 · A. Javaji🇨🇦 and 23 other authors

   Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, eight of which represent increases in precision over previous measurements. These measurements refine trends in the mass surface around $N=32$ and $N=34$, and support the disappearance of the $N=32$ shell closure with increasing proton number. Additionally, our data does not support the presence of a shell closure at $N=34$.

   nucl-exPRC(2022)·18 citations
2. 02*

   Applications of reduced basis methods to the nuclear single particle spectrum

   Amy L. Anderson · Graham L. O'Donnell · J. Piekarewicz🇺🇸

   Reduced basis methods provide a powerful framework for building efficient and accurate emulators. Although widely applied in many fields to simplify complex models, reduced basis methods have only been recently introduced into nuclear physics. In this letter we build an emulator to study the single-particle structure of atomic nuclei. By scaling a suitable mean-field Hamiltonian, a "universal" reduced basis is constructed capable of accurately and efficiently reproduce the entire single-particle spectrum of a variety of nuclei. Indeed, the reduced basis model reproduces both ground- and excited-state energies as well as the associated wave-functions with remarkable accuracy. Our results bode well for more demanding applications that use Bayesian optimization to calibrate nuclear energy density functionals.

   ↳ nucl-thnucl-exPRC(2022)·17 citations
3. 03*

   Uncertainty quantification of transition operators in the empirical shell model

   Jordan M. R. Fox🇺🇸 · Calvin W. Johnson🇺🇸 · Rodrigo Navarro Perez🇺🇸

   While empirical shell model calculations have successfully described low-lying nuclear data for decades, only recently has significant effort been made to quantify the uncertainty in such calculations. Here we quantify the statistical error in effective parameters for transition operators in empirical calculations in the $sd$ ($1s_{1/2}$-$0d_{3/2}$-$0d_{5/2}$) valence space, specifically the quenching of Gamow-Teller transitions, effective charges for electric quadrupole (E2) transitions, and the effective orbital and spin couplings for magnetic dipole (M1) transitions. We find the quenching factor for Gamow-Teller transitions relative to free-space values is tightly constrained and that the isoscalar coupling of E2 is much more tightly constrained than the isovector coupling. For effective M1 couplings, we found isovector components more constrained than isoscalar, but that to get any sensible result we had to fix one of four couplings. This detailed quantification of uncertainties, while highly empirical, nonetheless is an important step towards interpretation of experiments.

   ↳ nucl-thnucl-exPRC(2023)·4 citations
4. 04*

   Radiative neutron capture reaction rates for r-process nucleosynthesis

   Vinay Singh🇮🇳 · Joydev Lahiri🇮🇳 · Malay Kanti Dey · D. N. Basu🇮🇳

   About half of the elements beyond iron are synthesized in stars by rapid-neutron capture process (r-process). The stellar environment provides very high neutron flux in a short time ($\sim$ seconds) which is conducive for the creation of progressively neutron-rich nuclei till the waiting point is reached after which no further neutron capture reactions proceed. At this point such extremely neutron-rich nuclei become stable via ${\beta }^{-}$ decay. A detailed understanding of the r-process remains illusive. In the present work, we explore the radiative neutron-capture (n,$\gamma$) cross sections and reaction rates around the r-process peak near mass number eighty. The inherent uncertainties remain large in some cases, particularly in case of neutron-rich nuclei. When the low-energy enhancement exists, it results in significant increase in the reaction rate for neutron-capture.

   ↳ nucl-thastro-ph.SRnucl-exPramana(2023)·0 citations
5. 05*

   Sub-barrier fusion hindrance and absence of neutron transfer channels

   Vinay Singh🇮🇳 · Joydev Lahiri🇮🇳 · Partha Roy Chowdhury🇺🇸 · D. N. Basu🇮🇳

   The sub-barrier fusion hindrance has been observed in the domain of very low energies of astrophysical relevance. This phenomenon can be analyzed effectively using an uncomplicated straightforward elegant mathematical formula gleaned presuming diffused barrier with a Gaussian distribution. The mathematical formula for cross section of nuclear fusion reaction has been obtained by folding together a Gaussian function representing the fusion barrier height distribution and the expression for classical cross section of fusion assuming a fixed barrier. The variation of fusion cross section as a function of energy, thus obtained, describes well the existing data on sub-barrier heavy-ion fusion for lighter systems of astrophysical interest. Employing this elegant formula, cross sections of interacting nuclei from ${}^{16}$O + ${}^{18}$O to ${}^{12}$C + ${}^{198}$Pt, all of which were measured down to $<$ 10 $\mu$b have been analyzed. The agreement of the present analysis with the measured values is comparable, if not better, than those calculated from more sophisticated calculations. The three parameters of this formula varies rather smoothly implying its usage in estimating the excitation function or extrapolating cross sections for pairs of interacting nuclei which are yet to be measured. Possible effects of neutron transfers on the hindrance in heavy-ion fusion have been explored.

   ↳ nucl-thastro-ph.SRnucl-exIndian J.Phys.(2023)·0 citations
6. 06*

   Effective spectral function of vector mesons via lifetime analysis

   Renan Hirayama🇩🇪 · Jan Staudenmaier🇩🇪 · Hannah Elfner🇩🇪

   Effective spectral functions of the $\rho$ meson are reconstructed by considering the lifetimes inside different media using the hadronic transport SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). Due to inelastic scatterings, resonance lifetimes are dynamically shortened (collisional broadening), even though the employed approach assumes vacuum resonance properties. Analyzing the $\rho$ meson lifetimes allows to quantify an effective broadening of the decay width and spectral function, which is important in order to distinguish dynamical effects from additional genuine medium modifications to the spectral functions, indicating e.g. an onset of chiral symmetry restoration. The broadening of the spectral function in a thermalized system is shown to be consistent with other theoretical calculations. The effective $\rho$ meson spectral function is also presented for the dynamical evolution of heavy-ion collisions, finding a clear correlation of the broadening to system size, which is explained by an observed dependence of the width on the local hadron density. Furthermore, the difference in the results between the thermal system and full collision dynamics is explored, which may point to non-equilibrium effects.

   ↳ hep-phnucl-exnucl-thPRC(2023)·14 citations
7. 07*

   Effect of configuration mixing on quadrupole and octupole collective states of transitional nuclei

   Kosuke Nomura🇭🇷

   A model is presented that simultaneously describes shape coexistence and quadrupole and octupole collective excitations within a theoretical framework based on the nuclear density functional theory and the interacting boson model. An optimal interacting-boson Hamiltonian that incorporates the configuration mixing between normal and intruder states, as well as the octupole degrees of freedom, is identified by means of self-consistent mean-field calculations using a universal energy density functional and a pairing interaction, with constraints on the triaxial quadrupole and the axially-symmetric quadrupole and octupole shape degrees of freedom. An illustrative application to the transitional nuclei ${}^{72}$Ge, ${}^{74}$Se, ${}^{74}$Kr, and ${}^{76}$Kr shows that the inclusion of the intruder states and the configuration mixing significantly lower the energy levels of the excited $0^{+}$ states, and that the predicted low-lying positive-parity states are characterized by the strong admixture of nearly spherical, weakly deformed oblate, and strongly deformed prolate shapes. The low-lying negative-parity states are shown to be dominated by the deformed intruder configurations.

   ↳ nucl-thnucl-exPRC(2022)·10 citations
8. 08*

   Equation of State of Neutron-Rich Matter in $d$-Dimensions

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸

   Nuclear systems under constraints, with high degrees of symmetries and/or collectivities may be considered as moving effectively in spaces with reduced spatial dimensions. We first derive analytical expressions for the nucleon specific energy $E_0(\rho )$, pressure $P_0(\rho )$, incompressibility coefficient $K_0(\rho )$ and skewness coefficient $J_0(\rho )$ of symmetric nucleonic matter (SNM), the quadratic symmetry energy $E_{\mathrm{sym}}(\rho )$, its slope parameter $L(\rho )$ and curvature coefficient $K_{\mathrm{sym}}(\rho )$ as well as the fourth-order symmetry energy $E_{\mathrm{sym},4}(\rho )$ of neutron-rich matter in general $d$ spatial dimensions (abbreviated as "$d$D") in terms of the isoscalar and isovector parts of the isospin-dependent single-nucleon potential according to the generalized Hugenholtz-Van Hove (HVH) theorem. The equation of state (EOS) of nuclear matter in $d$D can be linked to that in the conventional 3-dimensional (3D) space by the $ϵ$-expansion which is a perturbative approach successfully used previously in treating second-order phase transitions and related critical phenomena and more recently in studying the EOS of cold atoms. The $ϵ$-expansion of nuclear EOS in $d$D based on a reference dimension $d_{\mathrm{f}}=d-ϵ$ is shown to be effective with $-1\lesssim ϵ\lesssim 1$ starting from $1\lesssim d_{\mathrm{f}}\lesssim 3$ in comparison with the exact expressions derived using the HVH theorem. Moreover, the EOS of SNM (with/without considering its potential part) is found to be reduced (enhanced) in lower (higher) dimensions, indicating in particular that the many-nucleon system tends to be deeper bounded but saturate at higher densities in spaces with lower dimensions. The links between the EOSs in 3D and $d$D spaces from the $ϵ$-expansion provide new perspectives to the EOS of neutron-rich matter.

   ↳ nucl-thastro-ph.HEnucl-exAnnals Phys.(2022)·13 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.