Nuclear Theory·nucl-th

Wednesday·January 22, 2020

18 papers—12 primary·6 cross-listed

01
Neutral-Current Neutrino Scattering from the Deuteron
Sabine Jeschonnek🇺🇸 · J. W. Van Orden🇺🇸 · T. W. Donnelly🇺🇸
Neutral-current neutrino scattering from the deuteron leading to proton-neutron final states is considered using an approach that incorporates relativistic dynamics and consequently provides robust modeling at relatively high energies and momenta. In this work the focus is placed on the fully exclusive reaction where both the proton and neutron in the final state are assumed to be detected. Accordingly, the incident neutrino energy, the neutrino scattering angle and the scattered neutrino's energy can all be reconstructed. It is shown that for specific choices of kinematics the reaction proceeds mainly via scattering from the proton, while for other choices of kinematics it proceeds mainly from the neutron. Specific asymmetries are introduced to focus on these attributes. Measurements in both regions have the potential to yield valuable information on the nucleon's electroweak form factors at momentum transfers up to a (GeV/c) $^{2}$ . In particular, the cross sections are shown to be very sensitive to the isoscalar axial-vector form factor, and sensitive but less so to the magnetic strangeness form factor. Comparisons with other reactions, specifically charge-changing neutrino reactions and both parity-conserving and -violating electron scattering, have the potential to provide new ways to test the Standard Model.
nucl-thhep-phPRC(2020)·0 citations
02
Deformed relativistic Hartree-Bogoliubov theory in continuum with point coupling functional: examples of even-even Nd isotopes
Kaiyuan Zhang · Myung-Ki Cheoun · Yong-Beom Choi · Pooi Seong Chong · Jianmin Dong · Lisheng Geng · Eunja Ha · Xiaotao He · Chan Heo · Meng Chit Ho · Eun Jin In · Seonghyun Kim and 26 other authors
The aim of this work is to develop the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) theory based on the point-coupling density functionals and extend it to provide a unified description for all even-even nuclei in the nuclear chart by overcoming all possible challenges. The nuclear superfluidity is considered via Bogoliubov transformation. Densities and potentials are expanded in terms of Legendre polynomials to include the axial deformation degrees of freedom. Sophisticated relativistic Hartree-Bogoliubov equations in coordinate space are solved in the DiracWoods-Saxon basis to consider the continuum effects. Numerical checks are performed from light nuclei to heavy nuclei. The techniques to construct the DRHBc mass table for even-even nuclei are explored. The DRHBc theory is extended to study heavier nuclei beyond magnesium isotopes. Taking Nd isotopes as examples, the experimental binding energies, two-neutron separation energies, quadrupole deformations, and charge radii are reproduced rather well. The deformation and continuum play essential roles in the description of nuclear masses and prediction of drip-line nuclei. By examining the single-particle levels in the canonical basis and their contributions to the total density, the thickness of the neutron skin, the particles number in continuum, and the Coulomb barrier, the exotic structures including the neutron skin and the proton radioactivity are predicted.
nucl-thnucl-exPRC(2020)·113 citations
03
Searching for small droplets of hydrodynamic fluid in proton--proton collisions at the LHC
Wenbin Zhao🇨🇳 · You Zhou🇩🇰 · Koichi Murase🇨🇳 · Huichao Song🇨🇳
In this paper, we investigate the hydrodynamic collectivity in high-multiplicity events of proton-proton collisions at $s =$ 13 TeV, using iEBE-VISHNU hybrid model with three different initial conditions, namely, HIJING, super-MC and TRENTo. With properly tuned parameters, hydrodynamic simulations with each initial model give reasonable descriptions of the measured two-particle correlations, including the integrated and $p_{T}$ -differential flow for all charged and identified hadrons. However, the hydrodynamic simulations fail to describe the negative value of the four-particle cumulant $c_{2}^{v} {4}$ as measured in experiments. Further investigations show that the non-linear response between the elliptic flow $v_{2}$ and the initial eccentricity $ε_{2}$ becomes significant in the small p-p systems. This leads to a large deviation from linear eccentricity scaling and generates additional flow fluctuations, which results in a positive $c_{2}^{v} {4}$ even with a negative $c_{2}^{ε} {4}$ from the initial state. We also presented the first hydrodynamic calculations of multi-particle mixed harmonic azimuthal correlations in p-p collisions, such as normalized asymmetric cumulant $na c_{n} {3}$ , normalized Symmetric-Cumulant, $n s c_{2, 3} {4}$ and $n s c_{2, 4} {4}$ . Although many qualitative features are reproduced by the hydrodynamic simulations with chosen parameters, the measured negative $n s c_{2, 3} {4}$ cannot be reproduced. The failure of the description of negative $c_{2} {4}$ and $n s c_{2, 3} {4}$ triggers the question on whether hydrodynamics with a fundamentally new initial state model could solve this puzzle, or hydrodynamics itself might not be the appreciated mechanism of the observed collectivity in p-p collisions at the LHC.
nucl-thhep-phnucl-exEPJC(2020)·43 citations
04
Neutron drip line of $Z = 9 - 11$ isotopic chains
Rong An · Guo-Fang Shen · Shi-Sheng Zhang · Li-Sheng Geng
A recent experimental breakthrough identified the last bound neutron-rich nuclei in fluorine and neon isotopes. Based on this finding, we perform a theoretical study of $Z = 9, 10, 11, 12$ isotopes in the relativistic mean field (RMF) model. The mean field parameters are assumed from the PK1 parameterization, and the pairing correlation is described by the particle number conservation BCS (FBCS) method recently formulated in the RMF model. We show that the FBCS approach plays an essential role in reproducing experimental results of fluorine and neon isotopes. Furthermore, we predict $^{39}$ Na and $^{40}$ Mg to be the last bound neutron-rich nuclei in sodium and magnesium isotopes.
nucl-thnucl-exCPC(2020)·6 citations
05
How to renormalize integral equations with singular potentials in effective field theory
E. Epelbaum🇩🇪 · A. M. Gasparyan🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇬🇪 · X.-L. Ren🇩🇪
We briefly review general concepts of renormalization in quantum field theory and discuss their application to solutions of integral equations with singular potentials in the few-nucleon sector of the low-energy effective field theory of QCD. We also describe a particular subtractive renormalization scheme and consider a specific application to a toy-model with a singular potential serving as its effective field theoretical leading-order approximation.
nucl-thhep-phhep-thEPJA(2020)·30 citations
06
Effect of magnetic screening mass on the diffusion of heavy quarks
Mahfuzur Rahaman🇮🇳 · Santosh K. Das🇮🇳 · Jan-e Alam🇮🇳 · Sabyasachi Ghosh🇮🇳
The drag and diffusion coefficients of heavy quarks propagating through quark gluon plasma (QGP) have been estimated by shielding both the electric and magnetic type infra-red divergences. The electric type screening in perturbative quantum chromodynamics (pQCD) has been widely studied and used in evaluating the diffusion coefficient of heavy quarks (HQs). To our knowledge the impact of magnetic screening in diffusion coefficients of HQs is not studied before. It is found that the effect of magnetic screening mass on the drag and diffusion coefficients of HQs is quite significant and its contribution should not be ignored for explaining the experimental data of heavy quark observables.
nucl-thhep-phIJMPE(2021)·3 citations
07
Reexamining the relation between the binding energy of finite nuclei and the equation of state of infinite nuclear matter
M. C. Atkinson · W. H. Dickhoff · M. Piarulli · A. Rios · R. B. Wiringa
The energy density is calculated in coordinate space for $^{12}$ C, $^{40}$ Ca, $^{48}$ Ca, and $^{208}$ Pb using a dispersive optical model constrained by all relevant data including the corresponding energy of the ground state. The energy density of $^{8}$ Be is also calculated using the Green's function Monte-Carlo method employing the Argonne/Urbana two and three-body interactions. The nuclear interior minimally contributes to the total binding energy due to the 4 $π r^{2}$ phase space factor. Thus, the volume contribution to the energy in the interior is not well constrained. The dispersive-optical-model energy densities are in good agreement with \textit{ab initio} self-consistent Green's function calculations of infinite nuclear matter restricted to treat only short-range and tensor correlations. These results call into question the degree to which the equation of state for nuclear matter is constrained by the empirical mass formula. In particular, the results in this paper indicate that saturated nuclear matter does not require the canonical value of 16 MeV binding per particle but only about 13-14 MeV when the interior of $^{208}$ Pb is considered.
nucl-thPRC(2020)·31 citations
08
Skyrme RPA for nuclear resonances: trouble with magnetic modes
J. Speth · P.-G. Reinhard · V. Tselyaev · N. Lyutorovich
We discuss major differences between electric and magnetic excitations in nuclei appearing in self-consistent calculation based on Skyrme energy-density functionals. Tools of analysis are Landau-Migdal parameters for bulk properties and RPA for resonance modes of $^{208}$ Pb as representative of finite nuclei. We show that the relation between the effective mass and the effective particle-hole interaction, well known in the Landau-Migdal theory, explains the success of self-consistent calculations of electric transitions in such approaches. This effect, however, does not automatically exist in the magnetic case. This calls for further developments of the Skyrme functional in the spin channel.
nucl-th5 citations
09
Shielding effects in fusion reactions of proton-halo nucleus
Xue-ying He🇨🇳 · Qin Dong🇨🇳 · Li Ou🇨🇳
To explain the experimental facts that the fusion cross sections of proton-halo nucleus on heavy target nucleus is not enhanced as expected, the shielding supposition has been proposed. Namely, the proton-halo nucleus is polarized with the valence proton being shielded by the core. In this paper, within the frame of the Improved Quantum Molecular Dynamics model, the fusion reactions by $^{17}$ F on $^{208}$ Pb around Coulomb barrier have been simulated. The existence of shielding effect is verified by microscopic dynamics analysis and its influence on the effective interaction potential is also investigated.
nucl-thCPC(2020)·4 citations
10
Microscopic study of the $^{7}$ Li-nucleus potential
Wen-Di Chen · Hai-Rui Guo · Wei-Li Sun · Tao Ye · Yang-Jun Ying · Yin-Lu Han · Qing-Biao Shen
The optical potential without any free parameters for $^{7}$ Li-nucleus interaction system is studied in a microscopic approach. It is obtained by folding the microscopic optical potentials of the constituent nucleons of $^{7}$ Li over their density distributions. We employ an isospin-dependent nucleon microscopic optical potential, which is based on the Skyrme nucleon-nucleon effective interaction and derived by using the Green's function method, to be the nucleon optical potential. Harmonic oscillator shell model is used to describe the internal wave function of $^{7}$ Li and get the nucleon density distribution. The $^{7}$ Li microscopic optical potential is used to predict the reaction cross sections and elastic scattering angular distributions for target range from $^{27}$ Al to $^{208}$ Pb and energy range below 450 MeV. Generally the results can reproduce the measured data reasonably well. In addition, the microscopic optical potential is comparable to a global phenomenological optical potential in fitting the presently existing measured data generally.
nucl-thCPC(2020)·5 citations
11
Localisation and alpha radioactivity
J.-P. Ebran🇫🇷 · E. Khan🇫🇷 · R.-D. Lasseri🇫🇷
Relativistic energy density functional approaches are known to well describe nuclear states which involve alpha clusters. Here, alpha emitting nuclei are analysed through the behavior of the spatial localisation of nucleonic states, calculated with an axially deformed RHB approach over the nuclear chart. The systematic occurrence of more localised valence states, having a n = 1 radial quantum number, allows to pinpoint nuclei in agreement with experimentally known alpha-emitters. The cases of 212Po and 104Te are investigated, showing the concomitant contributions of the pseudospin symmetry and the presence of n = 1 states, on the alpha preformation probability. The impact of the localisation of valence states, on alpha preformation probability, is then analysed. It allows to study shell effects on this probability, over isotopic and isotonic chains. Finally, a phenomenological law is also provided, relating this probability to the radial quantum number of the valence states.
nucl-thJ.Phys.G(2021)·2 citations
12
Electromagnetic transition rates of Carbon-12 and Oxygen-16 in rotational-vibrational models
C. J. Halcrow · J. I. Rawlinson
We develop a formalism to calculate electromagnetic (EM) transition rates for rotational-vibrational models of nuclei. The formalism is applied to recently proposed models of Carbon-12 and Oxygen-16 which are inspired by nuclear dynamics in the Skyrme model. We compare the results to experimental data, as well as other nuclear models. The results for Carbon-12 are in good agreement with the data across all models, making it difficult to differentiate the models. More experimental data is needed to do this, and we suggest which transitions would be most interesting to measure. The models of Oxygen-16 are less successful in describing the data, and we suggest some possible improvements to our approximations which may help.
nucl-thPRC(2020)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE