Nuclear Theory·nucl-th

Tuesday·October 24, 2017

22 papers—15 primary·7 cross-listed

01
[Submitted on 21 Oct 2017]
Phenomenological study of the pp -> pi+ pn reaction
G.Faeldt🇸🇪 · C.Wilkin🇬🇧
Fully constrained bubble chamber data on the pp -> pi+ pn and pp -> pi+ d reactions are used to investigate the ratio of the counting rates for the two processes as function of the pn excitation energy Q. Though it is important to include effects associated with the p-wave nature of pion production, the data are insufficient to establish unambiguously the dependence on Q. The angular distributions show the presence of higher partial waves which seem to be anomalously large at small Q. The dispersion relation method to determine scattering lengths is extended to encompass cases where, as for the pp -> pi+ pn reaction, there is a bound state and, in a test example, it is shown that the values deduced for the low energy neutron-proton scattering parameters are significantly influenced by the pion p-wave behavior.
Comments:
6 pages with 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.07812 [pdf]
PRC(2018)·0 citations
02
[Submitted on 22 Oct 2017]
Role of deformation in odd-even staggering in reaction cross sections for $^{30, 31, 32}$ Ne and $^{36, 37, 38}$ Mg isotopes
Y. Urata · K. Hagino · H. Sagawa
We discuss the role of pairing anti-halo effect in the observed odd-even staggering in reaction cross sections for $^{30, 31, 32}$ Ne and $^{36, 37, 38}$ Mg isotopes by taking into account the ground state deformation of these nuclei. To this end, we construct the ground state density for the $^{30, 31}$ Ne and $^{36, 37}$ Mg nuclei based on a deformed Woods-Saxon potential, while for the $^{32}$ Ne and $^{38}$ Mg nuclei we also take into account the pairing correlation using the Hartree-Fock-Bogoliubov method. We demonstrate that, when the one-neutron separation energy is small for the odd-mass nuclei, a significant odd-even staggering still appears even with finite deformation, although the degree of staggering is somewhat reduced compared to the spherical case. This implies that the pairing anti-halo effect in general plays an important role in generating the odd-even staggering in reaction cross sections for weakly bound nuclei.
Comments:
7 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.07884 [pdf]
PRC(2017)·21 citations
03
[Submitted on 22 Oct 2017]
Pure spin-3/2 propagator for use in particle and nuclear physics
J. Kristiano🇮🇩 · S. Clymton🇮🇩 · T. Mart🇮🇩
We propose the use of pure spin-3/2 propagator in the $(3/2, 0) \oplus (0, 3/2)$ representation in particle and nuclear physics. To formulate the propagator in a covariant form we use the antisymmetric tensor spinor representation and we consider the $Δ$ resonance contribution to the elastic $π N$ scattering as an example. We find that the use of conventional gauge invariant interaction Lagrangian leads to a problem; the obtained scattering amplitude does not exhibit the resonance behavior. To overcome this problem we modify the interaction by adding a momentum dependence. As in the case of Rarita-Schwinger we find that a perfect resonance description could be obtained in the pure spin-3/2 formulation only if hadronic form factors were considered in the interactions.
Comments:
5 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
arXiv:
1710.07930 [pdf]
PRC(2017)·15 citations
04
[Submitted on 22 Oct 2017]
Short range correlations and the isospin dependence of nuclear correlation functions
Reynier Cruz-Torres🇺🇸 · Axel Schmidt🇺🇸 · Gerald A. Miller🇺🇸 · Lawrence B. Weinstein🇺🇸 · Nir Barnea🇮🇱 · Ronen Weiss🇮🇱 · Eliezer Piasetzky🇮🇱 · Or Hen🇺🇸
Pair densities and associated correlation functions provide a critical tool for introducing many-body correlations into a wide-range of effective theories. Ab initio calculations show that two-nucleon pair-densities exhibit strong spin and isospin dependence. However, such calculations are not available for all nuclei of current interest. We therefore provide a simple model, which involves combining the short and long separation distance behavior using a single blending function, to accurately describe the two-nucleon correlations inherent in existing ab initio calculations. We show that the salient features of the correlation function arise from the features of the two-body short-range nuclear interaction, and that the suppression of the pp and nn pair-densities caused by the Pauli principle is important. Our procedure for obtaining pair-density functions and correlation functions can be applied to heavy nuclei which lack ab initio calculations.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.07966 [pdf]
PLB(2018)·43 citations
05
[Submitted on 22 Oct 2017]
Enhancements of high order cumulants across the 1st order phase transition boundary
Lijia Jiang🇩🇪 · Shanjin Wu🇨🇳 · Huichao Song🇨🇳
In this proceeding, we investigate the dynamical evolution of the $σ$ field with a trajectory across the 1st order phase transition boundary, using Langevin dynamics from the linear sigma model. We find the high order cumulants of the $σ$ field are largely enhanced during the dynamical evolution, compared with the equilibrium values, due to the supercooling effect of the first order phase transition.
Comments:
4 pages, 2 figures, SQM proceeding, with minor changes
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.08020 [pdf]
EPJ Web Conf.(2018)·7 citations
06
[Submitted on 22 Oct 2017]
Binding, bonding and charge symmetry breaking in $Λ$ -hypernuclei
Chhanda Samanta · Thomas A. Schmitt
Recent experiments have presented more accurate data on the $ΛΛ$ -binding energies of a few $ΛΛ$ - hypernuclei. This is important as the $ΛΛ$ - bond energies ( $Δ B_{ΛΛ}$ ) of double- $Λ$ hypernuclei provide a measure of the in-medium strength of the $ΛΛ$ interaction. A mass formula, optimized with the newly available $ΛΛ$ binding energy data, is used to estimate the binding energy and bond energy over a wide range of hypernuclei. The $Δ B_{ΛΛ}$ values calculated with this mass formula are in good agreement with the experimental data, predictions of the quark mean-field (QMF) model and the relativistic mean-field (RMF) model as well. The $ΛΛ$ -bond energy is found to diminish with neutron numbers, approaching zero near the neutron-drip line. In this formalism, the calculated binding energy difference in mirror nuclei arises from the Coulomb contributions and can be utilized to extract the Coulomb-corrected charge symmetry breaking effect.
Comments:
7 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08036 [pdf]
AIP Conf.Proc.(2019)·3 citations
07
[Submitted on 23 Oct 2017]
A description of pseudorapidity distributions of charged particles produced in Au+Au collisions at RHIC energies
Zhijin Jiang🇨🇳 · Dongfang Xu🇨🇳 · Yan Huang🇨🇳
The charged particles produced in heavy ion collisions consist of two parts: One is from the freeze-out of hot and dense matter formed in collisions. The other is from the leading particles. In this paper, the hot and dense matter is assumed to expand according to the hydrodynamic model including phase transition and decouples into particles via the prescription of Cooper-Frye. The leading particles are as usual supposed to have Gaussian rapidity distributions with the number equaling that of participants. The investigations of this paper show that, unlike low energy situations, the leading particles are essential in describing the pseudorapidity distributions of charged particles produced in high energy heavy ion collisions. This might be due to the different transparencies of nuclei at different energies.
Comments:
14 pages, 2 figures,1 table. arXiv admin note: text overlap with arXiv:1611.01247
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08078 [pdf]
Adv.High Energy Phys.(2018)·3 citations
08
[Submitted on 23 Oct 2017]
Microscopic core-quasiparticle coupling model for spectroscopy of odd-mass nuclei
S. Quan · W. P. Liu · Z. P. Li · M. S. Smith
Predictions of the spectroscopic properties of low-lying states are critical for nuclear structure studies, but are problematic for nuclei with an odd nucleon due to the interplay of the unpaired single particle with nuclear collective degrees of freedom. In this work, a microscopic core-quasiparticle coupling (CQC) model based on the covariant density functional theory is developed that contains the collective excitations of even-mass cores and spherical single-particle states of the odd nucleon as calculated from a quadrupole collective Hamiltonian combined with a constrained triaxial relativistic Hartree-Bogoliubov model. Predictions of the new model for excitation energies, kinematic and dynamic moments of inertia, and transition rates are shown to be in good agreement with results of low-lying spectroscopy measurements of the axially deformed odd-proton nucleus $^{159}$ Tb and the odd-neutron nucleus $^{157}$ Gd. Future studies with additional nuclei are planned.
Comments:
28 pages, 8 figures, 5 tables, Accepted for Publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08172 [pdf]
PRC(2017)·19 citations
09
[Submitted on 23 Oct 2017]
The Flow Constraint Influence on the Properties of Nuclear Matter Critical Endpoint
A. I. Ivanytskyi🇺🇦 · K. A. Bugaev🇺🇦 · V. V. Sagun🇺🇦 · L.V. Bravina🇳🇴 · E. E. Zabrodin🇳🇴
We propose a novel family of equations of state for symmetric nuclear matter based on the induced surface tension concept for the hard-core repulsion. It is shown that having only four adjustable parameters the suggested equations of state can, simultaneously, reproduce not only the main properties of the nuclear matter ground state, but the proton flow constraint up its maximal particle number densities. Varying the model parameters we carefully examine the range of values of incompressibility constant of normal nuclear matter and its critical temperature which are consistent with the proton flow constraint. This analysis allows us to show that the physically most justified value of nuclear matter critical temperature is 15.5-18 MeV, the incompressibility constant is 270-315 MeV and the hard-core radius of nucleons is less than 0.4 fm.
Comments:
8 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08218 [pdf]
PRC(2018)·31 citations
10
[Submitted on 23 Oct 2017]
Chiral interactions up to next-to-next-to-next-to-leading order and nuclear saturation
C. Drischler🇩🇪 · K. Hebeler🇩🇪 · A. Schwenk🇩🇪
We present an efficient Monte Carlo framework for perturbative calculations of infinite nuclear matter based on chiral two-, three-, and four-nucleon interactions. The method enables the incorporation of all many-body contributions in a straightforward and transparent way, and makes it possible to extract systematic uncertainty estimates by performing order-by-order calculations in the chiral expansion as well as the many-body expansion. The versatility of this new framework is demonstrated by applying it to chiral low-momentum interactions, exhibiting a very good many-body convergence up to fourth order. Following these benchmarks, we explore new chiral interactions up to next-to-next-to-next-to-leading order (N $^{3}$ LO). Remarkably, simultaneous fits to the triton and to saturation properties can be achieved, while all three-nucleon low-energy couplings remain natural. The theoretical uncertainties of nuclear matter are significantly reduced when going from next-to-next-to-leading order to N $^{3}$ LO.
Comments:
published version, incl. supplemental material
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
1710.08220 [pdf]
PRL(2019)·391 citations
11
[Submitted on 23 Oct 2017]
Spectroscopy of reflection-asymmetric nuclei with relativistic energy density functionals
S. Y. Xia · H. Tao · Y. Lu · Z. P. Li · T. Niksic · D. Vretenar
Quadrupole and octupole deformation energy surfaces, low-energy excitation spectra and transition rates in fourteen isotopic chains: Xe, Ba, Ce, Nd, Sm, Gd, Rn, Ra, Th, U, Pu, Cm, Cf, and Fm, are systematically analyzed using a theoretical framework based on a quadrupole-octupole collective Hamiltonian (QOCH), with parameters determined by constrained reflection-asymmetric and axially-symmetric relativistic mean-field calculations. The microscopic QOCH model based on the PC-PK1 energy density functional and $δ$ -interaction pairing is shown to accurately describe the empirical trend of low-energy quadrupole and octupole collective states, and predicted spectroscopic properties are consistent with recent microscopic calculations based on both relativistic and non-relativistic energy density functionals. Low-energy negative-parity bands, average octupole deformations, and transition rates show evidence for octupole collectivity in both mass regions, for which a microscopic mechanism is discussed in terms of evolution of single-nucleon orbitals with deformation.
Comments:
36 pages, 21 figures, Accepted for Publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08230 [pdf]
PRC(2017)·58 citations
12
[Submitted on 23 Oct 2017]
Microscopic analysis of octupole shape transitions in neutron-rich actinides with relativistic energy density functional
Zhong Xu · Zhi-Pan Li
Quadrupole and octupole deformation energy surfaces, low-energy excitation spectra, and electric transition rates in eight neutron-rich isotopic chains -- Ra, Th, U, Pu, Cm, Cf, Fm, and No -- are systematically analyzed using a quadrupole-octupole collective Hamiltonian model, with parameters determined by constrained reflection-asymmetric and axially-symmetric relativistic mean-field calculations based on the PC-PK1 energy density functional. The theoretical results of low-lying negative-parity bands, odd-even staggering, average octupole deformations $⟨ β_{3} ⟩$ , and $B (E 3; 3_{1}^{-} \to 0_{1}^{+})$ show evidence of a shape transition from nearly spherical to stable octupole-deformed, and finally octupole-soft equilibrium shapes in the neutron-rich actinides. A microscopic mechanism for the onset of stable octupole deformation is also discussed in terms of the evolution of single-nucleon orbitals with deformation.
Comments:
13 pages, 10 figures, Accepted for Publication in Chinese Physics C. arXiv admin note: substantial text overlap with arXiv:1710.08230; text overlap with arXiv:1402.6102 by other authors
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08238 [pdf]
CPC(2017)·26 citations
13
[Submitted on 23 Oct 2017]
Fermi liquid, clustering, and structure factor in dilute warm nuclear matter
Gerd Roepke · Dmitri Voskresensky · Ivan Kryukov · David Blaschke
Properties of nuclear systems at subsaturation densities can be obtained from different approaches. We demonstrate the use of the density autocorrelation function which is related to the isothermal compressibility and, after integration, to the equation of state. This way we connect the Landau Fermi liquid theory well elaborated in nuclear physics with the approaches to dilute nuclear matter describing cluster formation. A quantum statistical approach is presented, based on the cluster decomposition of the polarization function. The fundamental quantity to be calculated is the dynamic structure factor. Comparing with the Landau Fermi liquid theory which is reproduced in lowest approximation, the account of bound state formation and continuum correlations gives the correct low-density result as described by the second virial coefficient and by the mass action law (nuclear statistical equilibrium). Going to higher densities, the inclusion of medium effects is more involved compared with other quantum statistical approaches, but the relation to the Landau Fermi liquid theory gives a promising approach to describe not only thermodynamic but also collective excitations and non-equilibrium properties of nuclear systems in a wide region of the phase diagram.
Comments:
26 pages, 9 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08251 [pdf]
NPA(2018)·17 citations
14
[Submitted on 23 Oct 2017]
Octet Baryon Masses and Magnetic Moments in Hot and Dense Isospin Asymmetric Nuclear Matter
Harpreet Singh🇮🇳 · Arvind Kumar🇮🇳 · Harleen Dahiya🇮🇳
Medium modification of the magnetic moments of octet baryons in the isospin asymmetric nuclear medium at finite temperature has been calculated using medium modified quark and baryon masses derived in chiral SU(3) quark mean field model. The magnetic moments of baryons are found to vary significantly as a function of density of nuclear medium as well as with the increase in isospin asymmetry of the medium. The rise of temperature is found to decrease the effect of isospin asymmetry on masses and magnetic moments of baryons. The results of present investigation may be helpful to understand the experimentally observed values of octet baryon magnetic moments at different experimental facilities.
Comments:
37 pages, 8 figures, Accepted for publication in European Physical Journal Plus. arXiv admin note: text overlap with arXiv:1608.03388
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1710.08328 [pdf]
Eur.Phys.J.Plus(2019)·20 citations
15
[Submitted on 23 Oct 2017]
Pion production within the hybrid relativistic plane wave impulse approximation model at MiniBooNE and MINERvA kinematics
R. González-Jiménez🇧🇪 · K. Niewczas🇧🇪 · N. Jachowicz🇧🇪
The hybrid model for electroweak single-pion production (SPP) off the nucleon, presented in [González-Jiménez et al., Phys. Rev. D 95, 113007 (2017)], is extended here to the case of incoherent pion-production on the nucleus. Combining a low-energy model with a Regge approach, this model provides valid predictions in the entire energy region of interest for current and future accelerator-based neutrino-oscillation experiments. The Relativistic Mean-Field model is used for the description of the bound nucleons while the outgoing hadrons are considered as plane waves. This approach, known as Relativistic Plane-Wave Impulse Approximation (RPWIA), is a first step towards the development of more sophisticated models, it is also a test of our current understanding of the elementary reaction. We focus on the charged-current $ν$ ( $ν ˉ$ )-nucleus interaction at MiniBooNE and MINERvA kinematics. The effect on the cross sections of the final-state interactions, which affect the outgoing hadrons on their way out of the nucleus, is judged by comparing our results with those from the NuWro Monte Carlo event generator. We find that the hybrid-RPWIA predictions largely underestimate the MiniBooNE data. In the case of MINERvA, our results fall below the $ν$ -induced 1 $π^{0}$ production data, while a better agreement is found for $ν$ -induced 1 $π^{+}$ and $ν ˉ$ -induced 1 $π^{0}$ production.
Comments:
13 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.08374 [pdf]
PRD(2018)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE