Nuclear Theory·nucl-th

Tuesday·April 25, 2017

14 papers—8 primary·6 cross-listed

01
[Submitted on 21 Apr 2017]
The neutron skin thickness of $^{48}$ Ca from a nonlocal-dispersive-optical-model analysis
M.H. Mahzoon · M.C. Atkinson · R.J. Charity · W.H. Dickhoff
A nonlocal dispersive-optical-model analysis has been carried out for neutrons and protons in $^{48}$ Ca. Elastic-scattering angular distributions, total and reaction cross sections, single-particle energies, the neutron and proton numbers, and the charge distribution have been fitted to extract the neutron and proton self-energies both above and below the Fermi energy. From the single-particle propagator resulting from these self-energies we have determined the charge and neutron matter distributions in $^{48}$ Ca. A neutron skin of 0.249 $\pm$ 0.023~fm is deduced. The energy dependence of the total neutron cross sections is shown to have strong sensitivity to the skin thickness.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.06719 [pdf]
PRL(2017)·52 citations
02
[Submitted on 22 Apr 2017]
Charge redistribution from novel magneto-vorticity coupling in anomalous hydrodynamics
Koichi Hattori🇨🇳 · Yi Yin🇺🇸
We discuss new transport phenomena in the presence of both a strong magnetic field and a vortex field. Their interplay induces a charge distribution and a current along the magnetic field. We show that the associated transport coefficients can be obtained from a simple analysis of the single-particle distribution functions and also from the Kubo formula calculation. The consistent results from these analyses suggest that the transport coefficients are tied to the chiral anomaly in the (1+1) dimension because of the dimensional reduction in the lowest Landau levels.
Comments:
Contribution to the proceedings of Quark Matter 2017 in Chicago
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1704.06839 [pdf]
NPA(2017)·0 citations
03
[Submitted on 22 Apr 2017]
Equation of State of Quantum Gases Beyond the Van der Waals Approximation
K. A. Bugaev · A. I. Ivanytskyi · V. V. Sagun · E. G. Nikonov · G. M. Zinovjev
A recently suggested equation of state with the induced surface tension is generalized to the case of quantum gases with mean-field interaction. The self-consistency conditions of such a model and the necessary one to obey the Third Law of thermodynamics are found. The quantum virial expansion of the Van der Waals models of such a type is analyzed and its virial coefficients are given. In contrast to traditional beliefs, it is shown that an inclusion of the third and higher virial coefficients of the gas of hard spheres into the interaction pressure of the Van der Waals models either breaks down the Third Law of thermodynamics or does not allow one to go beyond the Van der Waals approximation at low temperatures. It is demonstrated that the generalized equation of state with the induced surface tension allows one to avoid such problems and to safely go beyond the Van der Waals approximation. Besides, the effective virial expansion for quantum version of the induced surface tension equation of state is established and all corresponding virial coefficients are found exactly.The explicit expressions for the true quantum virial coefficients of an arbitrary order of this equation of state are given in the low density approximation. A few basic constraints on such models which are necessary to describe the nuclear and hadronic matter properties are discussed.
Comments:
16 pages (extended version), 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.06846 [pdf]
Ukr.J.Phys.(2018)·15 citations
04
[Submitted on 23 Apr 2017]
Two-particle multiplets splitting as a guideline in nucleon pairing estimations
L.T. Imasheva (1) · B.S. Ishkhanov (1,2) · S.V. Sidorov (1) · M.E. Stepanov (1) · T.Yu. Tretyakova (2) ((1) Department of Physics, Lomonosov Moscow State University, (2) Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University)
The ground state multiplet structure for nuclei over the wide range of mass number $A$ was calculated in $δ$ -approximation and different mass relations for pairing energy was analysed in this work. Correlation between the calculated multiplet structure and experimental data offer a guideline in deciding between mass relations for nucleon pairing.
Comments:
6 pages, 2 fig., Proceedings of Intern. Session-Conference of the Section of Nuclear Physics of PSD RAS (April 12 - 15, 2016, JINR Dubna), to be published in Journal Physics of Elementary Particles and Atomic Nuclei (PEPAN)
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1704.06895 [pdf]
Phys.Part.Nucl.(2017)·4 citations
05
[Submitted on 23 Apr 2017]
Anomalous Transport Properties of Dense QCD in a Magnetic Field
Vivian de la Incera🇺🇸
Despite recent advancements in the study and understanding of the phase diagram of strongly interacting matter, the region of high baryonic densities and low temperatures has remained difficult to reach in the lab. Things are expected to change with the planned HIC experiments at FAIR in Germany and NICA in Russia, which will open a window to the high-density-low-temperature segment of the QCD phase map, providing a unique opportunity to test the validity of model calculations that have predicted the formation of spatially inhomogeneous phases with broken chiral symmetry at intermediate-to-high densities. Such a density region is also especially relevant for the physics of neutron stars, as they have cores that can have several times the nuclear saturation density. On the other hand, strong magnetic fields, whose presence is fairly common in HIC and in neutron stars, can affect the properties of these exotic phases and lead to signatures potentially observable in these two settings. In this paper, I examine the anomalous transport properties produced by the spectral asymmetry of the lowest Landau level (LLL) in a QCD-inspired NJL model with a background magnetic field that exhibits chiral symmetry breaking at high density via the formation of a Dual Chiral Density Wave (DCDW) condensate. It turns out that in this model the electromagnetic interactions are described by the axion electrodynamics equations and there is a dissipationless Hall current.
Comments:
Paper accepted for the Proceedings of the Workshop "Compact Stars at the QCD Phase Diagram V" held in L'Aquila, Italy, May 23-27, 2016
Subjects:
Nuclear Theory (nucl-th); cond-mat.mtrl-sci (cond-mat.mtrl-sci); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1704.06991 [pdf]
J.Phys.Conf.Ser.(2017)·1 citation
06
[Submitted on 24 Apr 2017]
Low-energy $η$ -nucleon interaction studied with $η$ photoproduction off the deuteron
S. X. Nakamura (1, 2)🇯🇵 · H. Kamano (3,4)🇯🇵 · T. Ishikawa (5,6) ((1) Osaka Univ., (2) Univ. Cruzeiro do Sul, (3) KEK, (4) J-PARC, (5) ELPH, (6) Tohoku Univ.)🇯🇵
We develop a reaction model for $η$ photoproduction off the deuteron ( $γ d \to η p n$ ), and study the reaction at a special kinematics, where the photon beam energy is $\sim 0.94$ GeV and the scattered proton is detected at $\sim 0^{\circ}$ , for the purpose of determining the $η$ -nucleon scattering length ( $a_{η N}$ ) and effective range ( $r_{η N}$ ). In this kinematics, the $η$ -nucleon elastic rescattering is significantly enhanced while other background mechanisms being suppressed. We show that a ratio $R$ , the $γ d \to η p n$ cross section divided by the $γ p \to η p$ cross section convoluted with the proton momentum distribution in the deuteron, has a very good resolving power of $a_{η N}$ and $r_{η N}$ . We conclude that the $R$ data with 5% error, binned in 1 MeV width of the $η$ -neutron invariant mass, can determine $Re [a_{η N}]$ ( $Re [r_{η N}]$ ) at the precision of $\sim \pm$ 0.1 fm ( $\sim \pm$ 0.5 fm), significantly narrowing down the previously estimated ranges of the parameters. To arrive at the conclusion, it is essential to use the $γ d \to η p n$ reaction model equipped with elementary amplitudes that are well constrained by $π N$ and $γ N$ reaction data through a sophisticated coupled-channels analysis. This result strongly motivates the Research Center for Electron Photon Science (ELPH) at Tohoku University to measure $R$ .
Comments:
6 pages, 6 figures, published version, 1 figure added, several references added, discussion on the previous works elaborated
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1704.07029 [pdf]
PRC(2017)·16 citations
07
[Submitted on 24 Apr 2017]
Shape-phase transitions in odd-mass $γ$ -soft nuclei with mass $A \approx 130$
K. Nomura · T. Nikšić · D. Vretenar
Quantum phase transitions between competing equilibrium shapes of nuclei with an odd number of nucleons are explored using a microscopic framework of nuclear energy density functionals and a particle-boson core coupling model. The boson Hamiltonian for the even-even core nucleus, as well as the spherical single-particle energies and occupation probabilities of unpaired nucleons, are completely determined by a constrained self-consistent mean-field calculation for a specific choice of the energy density functional and pairing interaction. Only the strength parameters of the particle-core coupling have to be adjusted to reproduce a few empirical low-energy spectroscopic properties of the corresponding odd-mass system. The model is applied to the odd-A Ba, Xe, La and Cs isotopes with mass $A \approx 130$ , for which the corresponding even-even Ba and Xe nuclei present a typical case of $γ$ -soft nuclear potential. The theoretical results reproduce the experimental low-energy excitation spectra and electromagnetic properties, and confirm that a phase transition between nearly spherical and $γ$ -soft nuclear shapes occurs also in the odd-A systems.
Comments:
13 pages, 15 figures, 9 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1704.07101 [pdf]
PRC(2017)·44 citations
08
[Submitted on 24 Apr 2017]
$K^{-}$ - nuclear states: Binding energies and widths
J. Hrtánková🇨🇿 · J. Mareš🇨🇿
$K^{-}$ optical potentials relevant to calculations of $K^{-}$ nuclear quasi-bound states were developed within several chiral meson-baryon coupled-channel interaction models. The applied models yield quite different $K^{-}$ binding energies and widths. Then, the $K^{-}$ multinucleon interactions were incorporated by a phenomenological optical potential fitted recently to kaonic atom data. Though the applied $K^{-}$ interaction models differ significantly in the $K^{-} N$ subthreshold region, our self-consistent calculations of kaonic nuclei across the periodic table lead to conclusions valid quite generally. Due to $K^{-}$ multinucleon absorption in the nuclear medium the calculated widths of $K^{-}$ nuclear states are sizable, $Γ_{K^{-}} \geq 90$ MeV, and exceed substantially their binding energies in all considered nuclei.
Comments:
25 pages, 24 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1704.07205 [pdf]
PRC(2017)·40 citations
09
[Submitted on 22 Apr 2017] (cross-list from hep-lat)
Connected and Disconnected Contractions in Pion-Pion Scattering
Neramballi Ripunjay Acharya🇨🇳 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Chien-Yeah Seng🇨🇳
We show that the interplay of chiral effective field theory and lattice QCD can be used in the evaluation of so-called disconnected diagrams, which appear in the study of the isoscalar and isovector channels of pion-pion scattering and have long been a major challenge for the lattice community. By means of partially-quenched chiral perturbation theory, we distinguish and analyze the effects from different types of contraction diagrams to the pion-pion scattering amplitude, including its scattering lengths and the energy-dependence of its imaginary part. Our results may be used to test the current degree of accuracy of lattice calculation in the handling of disconnected diagrams, as well as to set criteria for the future improvement of relevant lattice computational techniques that may play a critical role in the study of other interesting QCD matrix elements.
Comments:
18 pages, 3 figures, 3 tables
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.06754 [pdf]
NPB(2017)·15 citations
10
[Submitted on 23 Apr 2017] (cross-list from hep-ph)
Quarkonium as relativistic bound state on the light front
Yang Li🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸
We study charmonium and bottomonium as relativistic bound states in a light-front quantized Hamiltonian formalism. The effective Hamiltonian is based on light-front holography. We use a recently proposed longitudinal confinement to complete the soft-wall holographic potential for the heavy flavors. The spin structure is generated from the one-gluon exchange interaction with a running coupling. The adoption of asymptotic freedom improves the spectroscopy compared with previous light-front results. Within this model, we compute the mass spectroscopy, decay constants and the r.m.s. radii. We also present a detailed study of the obtained light-front wave functions and use the wave functions to compute the light-cone distributions, specifically the distribution amplitudes and parton distribution functions. Overall, our model provides a reasonable description of the heavy quarkonia.
Comments:
28 pages, 17 figures, 5 tables. Supplemental Materials are provided in the source file under "Other formats" (see also "Ancillary files")
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.06968 [pdf]
PRD(2017)·147 citations
11
[Submitted on 24 Apr 2017] (cross-list from nucl-ex)
Probing non-linearity of higher order anisotropic flow in Pb--Pb collisions
You Zhou (on behalf of the ALICE Collaboration)🇩🇰
The second and the third order anisotropic flow, $V_{2}$ and $V_{3}$ , are determined by the corresponding initial spatial anisotropy coefficients, $ε_{2}$ and $ε_{3}$ , in the initial density distribution. On the contrary, the higher order anisotropic flow $V_{n}$ ( $n > 3$ ), in addition to their dependence on the same order initial anisotropy coefficient $ε_{n}$ , have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this contribution, we present the investigations on linear and non-linear modes in higher order anisotropic flow ( $V_{4}$ , $V_{5}$ and $V_{6}$ ) in Pb--Pb collisions at $s_{NN} =$ 2.76 TeV using the ALICE detector at the Large Hadron Collider (LHC). A significant contribution from a non-linear mode is observed. A new observable, the non-linear response coefficient, is measured as well. The comparison to theoretical calculations provides crucial information on dynamic of the created system especially at the freeze-out conditions, which are poorly known from previous flow measurements.
Comments:
4 pages, 3 figures, XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017), Chicago, US
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1704.07070 [pdf]
NPA(2017)·1 citation
12
[Submitted on 24 Apr 2017] (cross-list from hep-ph)
Polyakov loop correlator in perturbation theory
Matthias Berwein🇯🇵 · Nora Brambilla🇩🇪 · Peter Petreczky🇺🇸 · Antonio Vairo🇩🇪
We study the Polyakov loop correlator in the weak coupling expansion and show how the perturbative series re-exponentiates into singlet and adjoint contributions. We calculate the order $g^{7}$ correction to the Polyakov loop correlator in the short distance limit. We show how the singlet and adjoint free energies arising from the re-exponentiation formula of the Polyakov loop correlator are related to the gauge invariant singlet and octet free energies that can be defined in pNRQCD, namely we find that the two definitions agree at leading order in the multipole expansion, but differ at first order in the quark-antiquark distance.
Comments:
58 pages, 2 figures; v2 journal version; v3 misprints corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1704.07266 [pdf]
PRD(2017)·22 citations
13
[Submitted on 24 Apr 2017] (cross-list from hep-ph)
Spin partners of the $Z_{b} (10610)$ and $Z_{b} (10650)$ revisited
V. Baru🇷🇺 · E. Epelbaum🇩🇪 · A. A. Filin🇩🇪 · C. Hanhart🇩🇪 · A. V. Nefediev🇷🇺
We study the implications of the heavy-quark spin symmetry for the possible spin partners of the exotic states $Z_{b} (10610)$ and $Z_{b} (10650)$ in the spectrum of bottomonium. We formulate and solve numerically the coupled-channel equations for the $Z_{b}$ states that allow for a dynamical generation of these states as hadronic molecules. The force includes short-range contact terms and the one-pion exchange potential, both treated fully nonperturbatively. The strength of the potential at leading order is fixed completely by the pole positions of the $Z_{b}$ states such that the mass and the most prominent contributions to the width of the isovector heavy-quark spin partner states $W_{b J}$ with the quantum numbers $J^{++}$ ( $J = 0, 1, 2$ ) come out as predictions. Since the accuracy of the present experimental data does not allow one to fix the pole positions of the $Z_{b}$ 's reliably enough, we also study the pole trajectories of their spin partner states as functions of the $Z_{b}$ binding energies. It is shown that, once the heavy-quark spin symmetry is broken by means of the physical $B$ and $B^{*}$ masses, especially the pion tensor force has a significant impact on the location of the partner states clearly demonstrating the need of a coupled-channel treatment of pion dynamics to understand the spin multiplet pattern of hadronic molecules.
Comments:
21 pages, 5 figures, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1704.07332 [pdf]
JHEP(2017)·52 citations
14
[Submitted on 24 Apr 2017] (cross-list from hep-lat)
Taming the Signal-to-Noise Problem in Lattice QCD by Phase Reweighting
Michael L. Wagman🇺🇸 · Martin J. Savage🇺🇸
Path integrals describing quantum many-body systems can be calculated with Monte Carlo sampling techniques, but average quantities are often subject to signal-to-noise ratios that degrade exponentially with time. A phase-reweighting technique inspired by recent observations of random walk statistics in correlation functions is proposed that allows energy levels to be extracted from late-time correlation functions with time-independent signal-to-noise ratios. Phase reweighting effectively includes dynamical refinement of source magnitudes but introduces a bias associated with the phase. This bias can be removed by performing an extrapolation, but at the expense of re-introducing a signal-to-noise problem. Lattice Quantum Chromodynamics calculations of the $ρ$ and nucleon masses and of the $ΞΞ$ binding energy show consistency between standard results obtained using earlier-time correlation functions and phase-reweighted results using late-time correlation functions inaccessible to standard statistical analysis methods.
Comments:
7 pages, 6 figures. Higher statistics, minor revisions
Subjects:
High Energy Physics — Lattice (hep-lat); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1704.07356 [pdf]
20 citations

Affiliations

first authorsco-authorsvia INSPIRE