Nuclear Theory·nucl-th

Friday·October 22, 2021

16 papers—7 primary·9 cross-listed

01
Two-Fermion Bound and Scattering States in a Finite Volume including QED in P-Wave and Beyond
Gianluca Stellin🇩🇪
Introducing a short range force coupling the spinless fermions to one unit of angular momentum in the framework of pionless EFT, we first report the two-body scattering amplitudes with Coulomb corrections, extended to two fermions of opposite charge in refs. [1,2]. Motivated by the growing interest in lattice approaches, we immerse the system into a cubic box with periodic boundary conditions and display the finite-volume corrections to the energy of the lowest bound and unbound $T_{1}^{-}$ eigenstates. The latter turn out to consist of power law terms proportional to the fine-structure constant. In the calculations, quadratic and higher order contributions in $α$ are discarded, on the grounds that the gapped nature of the momentum operator in the finite-volume environment allows for a perturbative treatment of the QED interactions. An outlook on the extension of the analysis to D-wave short-range interactions is eventually given.
nucl-thhep-latPoS(2022)·0 citations
02
Coupled-channel description for mirror mass-11 nuclei compared to shell-model structures
K. Amos · S. Karataglidis · L. Canton · P. R. Fraser · K. Murulane
The spectra of mass-11 nuclei are unusual, and so pose a challenge for theoretical models of their structure. The set of isobars range from being well bound to nucleon emission (11B,11C) through weakly bound (11Li, 11Be), with the former taking the form of a two neutron halo, to being proton unstable (11N,11O). A self-consistent approach to understand this set of nuclei is especially important as the mirror pair 11Be-11N exhibit a parity-inverted ground state compared to their neighbouring nuclei. Herein the Multi-Channel Algebraic Scattering (MCAS) method has been used to describe the low excitation spectra of those isobars in terms of nucleon-nucleus clusters. A collective model description of the low-excitation states of the mass-10 core nuclei has been used to form the coupled-channel interactions required in the method. For comparison, and to understand the underlying configurations, a shell model approach has been used to obtain those spectra with no-core (0+2+4)hw and (0+2)hw shell-model spaces for the mass 10 and mass 11 nuclei respectively.The results of the calculations suggest the need of a strong coupling in the collective coupled-channel vibrational model. In particular, the strong coupling of the collective 2+_1 state of 10Be to the valence neutron plays a decisive role in forming the positive parity ground state in11Be.
nucl-thEPJA(2022)·1 citation
03
Five-body resonances in $^{8}$ He and $^{8}$ C using the complex scaling method
Takayuki Myo · Myagmarjav Odsuren · Kiyoshi Katō
We study many-body resonances in the neuron-rich $^{8}$ He and the mirror proton-rich $^{8}$ C using the $^{4}$ He+ $N$ + $N$ + $N$ + $N$ five-body model with the isospin $T = 2$ system. Resonances are described with the complex energy eigenvalues as the Gamow states using the complex scaling method. In $^{8}$ He, we obtain five states, in which four states are resonances, and in $^{8}$ C all five states are resonances.We discuss the isospin-symmetry breaking dynamically induced by the Coulomb interaction in the energy spectra and decay widths of the resonances in two mirror nuclei. We predict the resonance energies and decay widths for the future experiments. We also investigate the configurations of valence nucleons above $^{4}$ He in two nuclei with the $j j$ coupling scheme and all the states dominantly have the $p$ -shell configurations. From the configuration mixing, $^{8}$ He and $^{8}$ C give the similar results, which indicates the good symmetry in two nuclei.
nucl-thPRC(2021)·17 citations
04
Reconciling multi-messenger constraints with chiral symmetry restoration
Michał Marczenko🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱
We analyze the recent astrophysical constraints in the context of a hadronic equation of state (EoS), in which the baryonic matter is subject to chiral symmetry restoration. We show that with such EoS it is possible to reconcile the modern constraints on the neutron star (NS) mass, radius, and tidal deformability (TD). We find that the softening of the EoS, required by the TD constraint of a canonical $1.4 M_{⊙}$ NS, followed by a subsequent stiffening, required by the $2 M_{⊙}$ constraint, is driven by the appearance of $Δ$ matter due to partial restoration of chiral symmetry. Consequently, a purely hadronic EoS that accounts for the fundamental properties of quantum chromodynamics linked to the dynamical emergence of parity doubling with degenerate masses of nucleons and $Δ$ resonances can be fully consistent with multi-messenger data. Therefore, with the present constraints on the EoS, the conclusion about the existence of the quark matter in the stellar core may still be premature.
nucl-thastro-ph.HEhep-phApJL(2022)·26 citations
05
Probing dense matter physics with transiently-accreting neutron stars: the case of source MXB 1659-29
Melissa Mendes · Farrukh J. Fattoyev · Andrew Cumming · Charles Gale
Recent observational data on transiently-accreting neutron stars has unequivocally shown fast-cooling sources, such as in the case of neutron star MXB 1659-29. Previous calculations have estimated its total neutrino luminosity and heat capacity, as well as suggested that direct Urca reactions take place in $1%$ of the volume of the core. In this paper, we reproduce the inferred luminosity of this source with detailed models of equations of state (EOS) and nuclear pairing gaps. We show that three superfluidity gap models are inconsistent with data for all EOS and another three are disfavoured because of fine tuning arguments. We also calculate the total heat capacity for all constructed stars and show that independent observations of mass and luminosity could set constraints on the core superfluidity of a source as well as the density slope of the symmetry energy, L. This is an important step towards defining a universal equation of state for neutron stars and therefore, towards a better understanding of the phase diagram of asymmetric matter at high densities.
nucl-thastro-ph.HEnucl-ex2 citations
06
The complete inverse Kohn-Sham problem: from the density to the energy
A. Liardi · F. Marino · G. Colò · X. Roca-Maza · E. Vigezzi
A complete solution to the inverse problem of Kohn-Sham (KS) density functional theory is proposed. Our method consists of two steps. First, the effective KS potential is determined from the ground state density of a given system. Then, the knowledge of the potentials along a path in the space of densities is exploited in a line integration formula to determine numerically the KS energy of that system. A possible choice for the density path is proposed. A benchmark in the case of a simplified yet realistic nuclear system is shown to be successful, so that the method seems promising for future applications.
nucl-thcond-mat.str-elPRC(2022)·2 citations
07
Nuclear medium effects in neutrino- and antineutrino-nucleus scattering
Natalie Jachowicz🇧🇪 · Alexis Nikolakopoulos🇨🇭
In this paper we study the influence of nuclear medium effects on quasi-elastic neutrino-nucleus scattering processes. We focus on effects provided by the nuclear mean field and random phase correlations and pay special attention to differences between neutrino- and antineutrino-induced reactions. We confront our results with the T2K and MiniBooNE data for both neutrinos and antineutrinos and the neutrino-antineutrino asymmetry. In view of the recently published ab initio results we provide a careful comparison between our cross section predictions and the ab-initio calculations.
nucl-thEur.Phys.J.ST(2021)·16 citations
08
Thermal effects on tidal deformability of a coalescing binary neutron star system
A. Kanakis-Pegios · P.S. Koliogiannis · Ch.C. Moustakidis
The study of neutron star mergers by the detection of the emitted gravitational waves is one of the most promised tools to study the properties of dense nuclear matter at high densities. It is worth claiming that, at the moment, strong evidence that the temperature of the stars is zero during the last orbits before coalescing does not exist. Contrariwise, there are some theoretical predictions suggesting that the star's temperature might even be a few MeV. According to the main theory, the tides transfer mechanical energy and angular momentum to the star at the expense of the orbit, where friction within the star converts the mechanical energy into heat. During the inspiral these effects are potentially detectable. Different treatments have been used to estimate the transfer of the mechanical energy and the size of the tidal friction, leading to different conclusions about the importance of pre-merger tidal effects. The present work is dedicated to the study of the effect of temperature on the tidal deformability of neutron stars during the inspiral of a neutron star system just before the merger. We applied a class of hot equations of state originated from various nuclear models and found that even for low values of temperature ( $T < 1$ MeV) the effects on the basic ingredients of tidal deformability are not negligible. However, according to the main finding, the effect of the temperature on the tidal deformability is indistinguishable. The consequences of this unexpected result are discussed and analyzed.
↳ astro-ph.HEnucl-thBulg.J.Phys.(2021)·0 citations
09
Nuclear data evaluation with Bayesian networks
Georg Schnabel · Roberto Capote · Arjan Koning · David Brown
Bayesian networks are graphical models to represent the probabilistic relationships between variables in the Bayesian framework. The knowledge of all variables can be updated using new information about some of the variables. We show that relying on the Bayesian network interpretation enables large scale inference and gives flexibility in incorporating prior assumptions and constraints into the nuclear data evaluation process, such as sum rules and the non-negativity of cross sections. The latter constraint is accounted for by a non-linear transformation and therefore we also discuss inference in Bayesian networks with non-linear relationships. Using Bayesian networks, the evaluation process yields detailed information, such as posterior estimates and uncertainties of all statistical and systematic errors. We also elaborate on a sparse Gaussian process construction compatible with the Bayesian network framework that can for instance be used as prior on energy-dependent model parameters, model deficiencies and energy-dependent systematic errors of experiments. We present three proof-of-concept examples that emerged in the context of the neutron data standards project and in the ongoing international evaluation efforts of $^{56}$ Fe. In the first example we demonstrate the modelization and explicit estimation of relative energy-dependent error components of experimental datasets. Then we show an example evaluation using the outlined Gaussian process construction in an evaluation of $^{56}$ Fe in the energy range between one and two MeV, where R-Matrix and nuclear model fits are difficult. Finally, we present a model-based evaluation of $^{56}$ Fe between 5 MeV and 30 MeV with a sound treatment of model deficiencies. The R scripts to reproduce the Bayesian network examples and the nucdataBaynet package for Bayesian network modeling and inference have been made publicly available.
↳ physics.data-annucl-exnucl-th3 citations
10
Axial inverse magnetic catalysis
Yuanyuan Wang🇨🇳 · Shinya Matsuzaki🇨🇳
We find that the inverse magnetic catalysis for $U (1)$ axial symmetry (AIMC: axial inverse magnetic catalysis) can emerge around the chiral crossover regime in the thermomagnetic QCD with 2 + 1 flavors at physical point. This phenomenon can be correlated with the IMC for the chiral $S U (2)_{L} \times S U (2)_{R}$ symmetry (CIMC: chiral IMC). We explicitly observe the AIMC based on a Nambu-Jona-Lasinio model with 2 + 1 quark flavors, where introduced anomalous magnetic moments of the quarks play the essential role to drive both the CIMC and AIMC. Our finding is shortly testable on lattices. Possible phenomenological and cosmological implications are also briefly addressed.
↳ hep-phhep-latnucl-thPRD(2022)·6 citations
11
Analysis of two-nucleon transfer reactions in the 20Ne + 116Cd system at 306 MeV
D. Carbone🇮🇹 · J. L. Ferreira🇧🇷 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · M. Cavallaro🇮🇹 · A. Hacisalihoglu🇹🇷 · H. Lenske🇩🇪 · J. Lubian🇧🇷 · R. I. Magana Vsevolodovna🇮🇹 · E. Santopinto🇮🇹 · C. Agodi🇮🇹 · L. Acosta🇲🇽 and 37 other authors
Background: Heavy-ion induced two-nucleon transfer reactions are powerful tools to reveal peculiar aspects of the atomic nucleus, such as pairing correlations, single-particle and collective degrees of freedom, and more. Also, these processes are in competition with the direct meson exchange in the double charge exchange reactions, which have recently attracted great interest due to their possible connection to neutrinoless double-beta decay. In this framework, the exploration of two-nucleon transfer reactions in the 20Ne+116Cd collision at energies above the Coulomb barrier is particularly relevant since the 116Cd nucleus is a candidate for the double-beta decay. Methods: We measured the excitation energy spectra and absolute cross sections for the two reactions using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. We performed direct coupled reaction channels and sequential distorted wave Born approximation calculations using the double folding São Paulo potential to model the initial and final state interactions. The spectroscopic amplitudes for two- and singleparticle transitions were derived by different nuclear structure approaches: microscopic large-scale shell model, interacting boson model-2 and quasiparticle random phase approximation. Results: The calculations are able to reproduce the experimental cross sections for both two-neutron and twoproton transfer reactions. The role of couplings with the inelastic channels are found to be important in the two-proton transfer case. A competition between the direct and the sequential process is found in the reaction mechanism. For the two-proton transfer case, the inclusion of the 1g7/2 and 2d5/2 orbitals in the model space is crucial.
↳ nucl-exnucl-thPRC(2020)·54 citations
12
Study of one-proton transfer reaction for the $^{18}$ O + $^{48}$ Ti system at 275 MeV
O. Sgouros🇮🇹 · M. Cavallaro🇮🇹 · F. Cappuzzello🇮🇹 · D. Carbone🇮🇹 · C. Agodi🇮🇹 · A. Gargano🇮🇹 · G. De Gregorio🇮🇹 · C. Altana🇮🇹 · G. A. Brischetto🇮🇹 · S. Burrello🇫🇷 · S. Calabrese🇮🇹 · D. Calvo🇮🇹 and 29 other authors
Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction $^{48}$ Ti( $^{18}$ O, $^{19}$ F) $^{47}$ Sc at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the $^{19}$ F ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the São Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space.
↳ nucl-exnucl-thPRC(2021)·41 citations
13
Entanglement Structures in Quantum Field Theories: Negativity Cores and Bound Entanglement in the Vacuum
Natalie Klco🇺🇸 · D. H. Beck🇺🇸 · Martin J. Savage🇺🇸
The many-body entanglement between two finite (size- $d$ ) disjoint vacuum regions of non-interacting lattice scalar field theory in one spatial dimension -- a $(d_{A} \times d_{B})_{mixed}$ Gaussian continuous variable system -- is locally transformed into a tensor-product "core" of $(1_{A} \times 1_{B})_{mixed}$ entangled pairs. Accessible entanglement within these core pairs exhibits an exponential hierarchy, and as such identifies the structure of dominant region modes from which vacuum entanglement could be extracted into a spatially separated pair of quantum detectors. Beyond the core, remaining modes of the "halo" are determined to be AB-separable in isolation, as well as separable from the core. However, state preparation protocols that distribute entanglement in the form of $(1_{A} \times 1_{B})_{mixed}$ core pairs are found to require additional entanglement in the halo that is obscured by classical correlations. This inaccessible (bound) halo entanglement is found to mirror the accessible entanglement, but with a step behavior as the continuum is approached. It remains possible that alternate initialization protocols that do not utilize the exponential hierarchy of core-pair entanglement may require less inaccessible entanglement. Entanglement consolidation is expected to persist in higher dimensions and may aid classical and quantum simulations of asymptotically free gauge field theories, such as quantum chromodynamics.
↳ quant-phhep-lathep-phhep-th+1PRA(2023)·35 citations
14
Accelerating quantum many-body configuration interaction with directives
Brandon Cook · Patrick J. Fasano · Pieter Maris · Chao Yang · Dossay Oryspayev
Many-Fermion Dynamics-nuclear, or MFDn, is a configuration interaction (CI) code for nuclear structure calculations. It is a platform-independent Fortran 90 code using a hybrid MPI+X programming model. For CPU platforms the application has a robust and optimized OpenMP implementation for shared memory parallelism. As part of the NESAP application readiness program for NERSC's latest Perlmutter system, MFDn has been updated to take advantage of accelerators. The current mainline GPU port is based on OpenACC. In this work we describe some of the key challenges of creating an efficient GPU implementation. Additionally, we compare the support of OpenMP and OpenACC on AMD and NVIDIA GPUs.
↳ cs.DCcs.CEcs.MScs.PF+11 citation
15
Analysis of two-proton transfer in the 40Ca(18O,20Ne)38Ar reaction at 270 MeV incident energy
J. L. Ferreira🇧🇷 · D. Carbone🇮🇹 · M. Cavallaro🇮🇹 · N. N. Deshmukh🇮🇹 · C. Agodi🇮🇹 · G. A. Brischetto🇮🇹 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · E. N. Cardozo🇧🇷 · I. Ciraldo🇮🇹 · M. Cutuli🇮🇹 · M. Fisichella🇮🇹 and 7 other authors
Two-nucleon transfer reactions are essential tools to investigate specific features of the nuclearstructure such as the correlation among valence particles in the transfer process. Besides, transfer reactions may be an important channel to take into account in charge exchange processes since they can represent a competing contribution to the final cross section. The two-proton pickup transfer reaction 40Ca(18O,20Ne)38Ar has been measured at 270 MeV and the angular distributions for transitions to different excited states extracted. This work shows the analysis of the data performed by finite range coupled reaction channel and coupled channel Born approximation methods. Extensive shell-model calculations are performed to derive the one- and two-proton spectroscopic amplitudesfor the projectile and target overlaps. The role of the simultaneous and sequential two-proton transfer mechanisms to populate the measured final states or groups of states, mainly characterized by ahigh collectivity, is also discussed.
↳ nucl-exnucl-thPRC(2021)·43 citations
16
Electron Captures and Stability of White Dwarfs
N. Chamel🇧🇪 · L. Perot🇧🇪 · A. F. Fantina🇫🇷 · D. Chatterjee🇮🇳 · S. Ghosh🇮🇳 · J. Novak🇫🇷 · M. Oertel🇫🇷
Electron captures by atomic nuclei in dense matter are among the most important processes governing the late evolution of stars, limiting in particular the stability of white dwarfs. Despite considerable progress in the determination of the equation of state of dense Coulomb plasmas, the threshold electron Fermi energies are still generally estimated from the corresponding $Q$ values in vacuum. Moreover, most studies have focused on nonmagnetized matter. However, some white dwarfs are endowed with magnetic fields reaching $1 0^{9}$ G. Even more extreme magnetic fields might exist in super Chandrasekhar white dwarfs, the progenitors of overluminous type Ia supernovae like SN 2006gz and SN 2009dc. The roles of the dense stellar medium and magnetic fields on the onset of electron captures and on the structure of white dwarfs are briefly reviewed. New analytical formulas are derived to evaluate the threshold density for the onset of electron captures for arbitrary magnetic fields. Their influence on the structure of white dwarfs is illustrated by simple analytical formulas and numerical calculations.
↳ astro-ph.SRastro-ph.HEnucl-thThe Sixteenth Marcel Grossmann Meeting, p…·1 citation

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