Nuclear Theory·nucl-th

Tuesday·December 13, 2016

10 papers—6 primary·4 cross-listed

01
[Submitted on 10 Dec 2016]
Chaos and regularity in the doubly magic nucleus 208Pb
B. Dietz · A. Heusler · K. H. Maier · A. Richter · B. A. Brown
High resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation Energy of Ex= 6.20 MeV in 208Pb. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach we grouped states with the same spin and parity into 14 subspectra, analyzed standard statistical measures for short- and long-range correlations and then computed their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian Orthogonal Ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter we considered the complete spectrum composed of the independent subspectra. We analyzed their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f~0.9. This is so far the closest agreement with GOE observed in spectra of bound states in a nucleus. The same analysis has also been performed with spectra computed on the basis of shell model calculations with different interactions (SDI, KB, M3Y). While the simple SDI exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.
Subjects:
Nuclear Theory (nucl-th); nlin.CD (nlin.CD); Nuclear Experiment (nucl-ex)
arXiv:
1612.03260 [pdf]
PRL(2017)·26 citations
02
[Submitted on 10 Dec 2016]
Effect of meson cloud on the jet nuclear modification factor in $p A$ collisions
B.G. Zakharov🇷🇺
We study the effect of the nucleon meson cloud on centrality dependence of the jet nuclear modification factor $R_{p A}$ . We find that the meson-baryon Fock components may lead to a noticeable deviation of $R_{p A}$ from unity. Our results for $R_{p A}$ show the same tendency as that observed by ATLAS in $p + P b$ collisions at $s = 5.02$ TeV. The meson cloud suppresses the central jet events and enhances the peripheral jet events. But quantitatively the effect is somewhat smaller than in the data.
Comments:
5 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.03337 [pdf]
JETP Lett.(2017)·1 citation
03
[Submitted on 12 Dec 2016]
Neutrino Processes with Hot Nuclei in Supernovae
Alan A. Dzhioev🇷🇺 · A. I. Vdovin🇷🇺
In this paper, we calculate cross sections for charged-current neutrino-nucleus processes occuring under presupernova conditions. To treat thermal effects we extend self-consistent Skyrme-QRPA calculations to finite temperature by using the formalism of thermo field dynamics. The numerical results are presented for the sample nuclei, $^{56}$ Fe and $^{82}$ Ge
Comments:
Contribution to the Proceedings of the 2016 Zakopane Conference on Nuclear Physics, Zakopane, Poland, August 28 - September 4, 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.03611 [pdf]
Acta Phys.Polon.B(2017)·2 citations
04
[Submitted on 12 Dec 2016]
Lambda-nuclear interactions and hyperon puzzle in neutron stars
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪 · N. Kaiser🇩🇪 · W. Weise🇩🇪
Brueckner theory is used to investigate the in-medium properties of a $Λ$ -hyperon in nuclear and neutron matter, based on hyperon-nucleon interactions derived within SU(3) chiral effective field theory (EFT). It is shown that the resulting $Λ$ single-particle potential $U_{Λ} (p_{Λ} = 0, ρ)$ becomes strongly repulsive for densities $ρ$ of two-to-three times that of normal nuclear matter. Adding a density-dependent effective $Λ N$ -interaction constructed from chiral $Λ N N$ three-body forces increases the repulsion further. Consequences of these findings for neutron stars are discussed. It is argued that for hyperon-nuclear interactions with properties such as those deduced from the SU(3) EFT potentials, the onset for hyperon formation in the core of neutron stars is expected to be shifted to extremely high baryon density, thus potentially resolving the so-called hyperon puzzle.
Comments:
6 pages, two figures; longer discussion about uncertainties added
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1612.03758 [pdf]
EPJA(2017)·81 citations
05
[Submitted on 12 Dec 2016]
Interaction between antiprotonic helium ion and He atom: Potential Energy Surface
S. N. Yudin (1) · I. V. Bodrenko (2) · G. Ya. Korenman (1) ((1) Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia (2) Department of Physics, University of Cagliari, Cagliari, Italy)
Potential Energy Surface for the ( $p ˉ - He^{2 +} - He$ ) system is calculated in the framework of the restricted (singlet spin state) Hartree-Fock method with subsequent account of the electronic correlations within the second order perturbation method (MP2). The geometry of heavy particles is described in variables of distance $r$ from nucleus $a$ to antiproton, distance $R$ from the center of mass of the $(p ˉ - a)$ pair to $He$ atom containing nucleus $b$ , and an angle $θ$ between $r$ and $R$ . The potential $V (R, r, cos θ)$ of the interaction between $He$ atom and a $p ˉ - a$ subsystem involves a total energy of two electrons in the field of three heavy particles and Coulomb interactions of the $b$ nucleus with antiproton and the $a$ nucleus. The expansion of this potential in terms of Legendre polynomials $P_{k} (cos θ)$ is obtained. Matrices of the multipole terms $V^{k} (r, R)$ ( $k = 0, 1, 2$ ) are obtained in the basis of antiprotonic helium ion states. The results are compared with the model potential that was used earlier in the calculations of collisional Stark transitions of $(p ˉ He^{2 +})$ ion.Total cross sections of collisional Stark transitions obtained with the PES potentials exceed the model results by 15 - 20\% at $E \leq 12$ K.
Comments:
11 pages, 18 fugures
Subjects:
Nuclear Theory (nucl-th); physics.chem-ph (physics.chem-ph); Quantum Physics (quant-ph)
arXiv:
1612.03874 [pdf]
1 citation
06
[Submitted on 12 Dec 2016]
Impact of resonance decays on critical point signals in net-proton fluctuations
Marcus Bluhm (North Carolina State U.)🇺🇸 · Marlene Nahrgang (SUBATECH, Nantes & Duke U.)🇫🇷 · Steffen A. Bass (Duke U.)🇺🇸 · Thomas Schaefer (North Carolina State U.)🇺🇸
The non-monotonic beam energy dependence of the higher cumulants of net-proton fluctuations is a widely studied signature of the conjectured presence of a critical point in the QCD phase diagram. In this work we study the effect of resonance decays on critical fluctuations. We show that resonance effects reduce the signatures of critical fluctuations, but that for reasonable parameter choices critical effects in the net-proton cumulants survive. The relative role of resonance decays has a weak dependence on the order of the cumulants studied with a slightly stronger suppression of critical effects for higher-order cumulants.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.03889 [pdf]
EPJC(2017)·34 citations
07
[Submitted on 11 Dec 2016] (cross-list from hep-lat)
Towards a theoretical description of dense QCD
Owe Philipsen🇩🇪
The properties of matter at finite baryon densities play an important role for the astrophysics of compact stars as well as for heavy ion collisions or the description of nuclear matter. Because of the sign problem of the quark determinant, lattice QCD cannot be simulated by standard Monte Carlo at finite baryon densities. I review alternative attempts to treat dense QCD with an effective lattice theory derived by analytic strong coupling and hopping expansions, which close to the continuum is valid for heavy quarks only, but shows all qualitative features of nuclear physics emerging from QCD. In particular, the nuclear liquid gas transition and an equation of state for baryons can be calculated directly from QCD. A second effective theory based on strong coupling methods permits studies of the phase diagram in the chiral limit on coarse lattices.
Comments:
10 pages, 9 figures; Contribution to the "12th Quark Confinement and the Hadron Spectrum" conference, Thessaloniki, 28.08.-04.09.2016
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.03400 [pdf]
EPJ Web Conf.(2017)·10 citations
08
[Submitted on 11 Dec 2016] (cross-list from hep-ph)
Relation between the mass modification of the heavy-light mesons and the chiral symmetry structure in dense matter
Masayasu Harada🇯🇵 · Yong-Liang Ma🇨🇳 · Daiki Suenaga🇯🇵 · Yusuke Takeda🇯🇵
We point out that the study of the density dependences of the masses of heavy-light mesons give some clues to the chiral symmetry structure in nuclear matter. We include the omega meson effect as well as the sigma meson effect at mean field level on the density dependence of the masses of heavy-light mesons with chiral partner structure. It is found that the omega meson affects the masses of the heavy-light mesons and their antiparticles in the opposite way, while it affects the masses of chiral partners in the same way. This is because the omega meson is sensitive to the baryon number of the light degrees included in the heavy-light mesons. We also show that the mass difference between chiral partners is proportional to the mean field of sigma, reflecting the partial restoration of chiral symmetry in the nuclear matter. In addition to the general illustration of the density dependence of the heavy-light meson masses, we consider two concrete models for nuclear matter, the parity doublet model and skyrmion crystal model in the sense of mean field approximation.
Comments:
7 pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1612.03496 [pdf]
PTEP(2017)·21 citations
09
[Submitted on 12 Dec 2016] (cross-list from hep-ph)
Phase Structure and Dynamics of QCD-- A Functional Perspective
Nils Strodthoff🇺🇸
The understanding of the phase structure and the fundamental properties of QCD matter from its microscopic description requires appropriate first-principle approaches. Here I review the progress towards a quantitative first-principle continuum approach within the framework of the Functional Renormalization group established by the fQCD collaboration. I focus on recent quantitative results for quenched QCD and Yang-Mills theory in the vacuum before addressing the calculation of dynamical quantities such as spectral functions and transport coefficients in this framework.
Comments:
4 pages, 4 figures, contribution to the proceedings of the Hot Quarks 2016 conference at South Padre Island, TX, USA
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1612.03807 [pdf]
J.Phys.Conf.Ser.(2017)·6 citations
10
[Submitted on 7 Dec 2016] (cross-list from physics.ins-det)
Spatial heterogeneity of W transmutation in a fusion device
M. R. Gilbert · J.-Ch. Sublet · S. L. Dudarev
Accurately quantifying the transmutation rate of tungsten (W) under neutron irradiation is a necessary requirement in the assessment of its performance as an armour material in a fusion power plant. The usual approach of calculating average responses, assuming large, homogenised material volumes, is insufficient to capture the full complexity of the transmutation picture in the context of a realistic fusion power plant design, particularly for rhenium (Re) production from W. Combined neutron transport and inventory simulations for representative {\it spatially heterogeneous} models of a fusion power plant show that the production rate of Re is strongly influenced by the local spatial environment. Localised variation in neutron moderation (slowing down) due to structural steel and coolant, particularly water, can dramatically increase Re production because of the huge cross sections of giant resolved resonances in the neutron-capture reaction of $^{186}$W at low neutron energies. Calculations using cross section data corrected for temperature (Doppler) effects suggest that temperature may have a relatively lesser influence on transmutation rates.
Comments:
9 pages, 10 figures
Subjects:
Instrumentation and Detectors (physics.ins-det); Nuclear Theory (nucl-th)
arXiv:
1612.03892 [pdf]
Nucl.Fusion(2017)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE