Nuclear Theory·nucl-th

Tuesday·July 7, 2015

11 papers—8 primary·3 cross-listed

01
Reaction-diffusion equation for quark-hadron transition in heavy-ion collisions
Partha Bagchi🇮🇳 · Arpan Das🇮🇳 · Srikumar Sengupta🇮🇳 · Ajit M. Srivastava🇮🇳
Reaction-diffusion equations with suitable boundary conditions have special propagating solutions which very closely resemble the moving interfaces in a first order transition. We show that the dynamics of chiral order parameter for chiral symmetry breaking transition in heavy-ion collisions, with dissipative dynamics, is governed by one such equation, specifically, the Newell-Whitehead equation. Further, required boundary conditions are automatically satisfied due to the geometry of the collision. The chiral transition is, therefore, completed by a propagating interface, exactly as for a first order transition, even though the transition actually is a crossover for relativistic heavy-ion collisions. Same thing also happens when we consider the initial confinement-deconfinement transition with Polyakov loop order parameter. The resulting equation, again with dissipative dynamics, can then be identified with the reaction-diffusion equation known as the Fitzhugh-Nagumo equation which is used in population genetics. We discuss the implications of these results for heavy-ion collisions. We also discuss possible extensions for the case of early universe.
nucl-thcond-mat.stat-mechhep-phnlin.PS+1PRC(2015)·1 citation
02
Relativistic model for the nonmesonic weak decay of single-lambda hypernuclei
C.E. Fontoura🇧🇷 · F. Krmpotić🇧🇷 · A.P. Galeão🇧🇷 · C. De Conti🇧🇷 · G. Krein🇧🇷
Having in mind its future extension for theoretical investigations related to charmed nuclei, we develop a relativistic formalism for the nonmesonic weak decay of single- $Λ$ hypernuclei in the framework of the independent-particle shell model and with the dynamics represented by the $(π, K)$ one-meson-exchange model. Numerical results for the one-nucleon-induced transition rates of $_{Λ}^{12} C$ are presented and compared with those obtained in the analogous nonrelativistic calculation. There is satisfactory agreement between the two approaches, and the most noteworthy difference is that the ratio $Γ_{n} / Γ_{p}$ is appreciably higher and closer to the experimental value in the relativistic calculation. Large discrepancies between ours and previous relativistic calculations are found, for which we do not encounter any fully satisfactory explanation. The most recent experimental data is well reproduced by our results. In summary, we have achieved our purpose to develop a reliable model for the relativistic calculation of the nonmesonic weak decay of $Λ$ -hypernuclei, which can now be extended to evaluate similar processes in charmed nuclei.
nucl-thJ.Phys.G(2016)·2 citations
03
Halos in medium-heavy and heavy nuclei with covariant density functional theory in continuum
Jie Meng🇨🇳 · Shan-Gui Zhou🇨🇳
The covariant density functional theory with a few number of parameters has been widely used to describe the ground-state and excited-state properties for the nuclei all over the nuclear chart. In order to describe exotic properties of unstable nuclei, the contribution of the continuum and its coupling with bound states should be treated properly. In this Topical Review, the development of the covariant density functional theory in continuum will be introduced, including the relativistic continuum Hartree-Bogoliubov theory, the relativistic Hartree-Fock-Bogoliubov theory in continuum, and the deformed relativistic Hartree-Bogoliubov theory in continuum. Then the descriptions and predictions of the neutron halo phenomena in both spherical and deformed nuclei will be reviewed. The diffuseness of the nuclear potentials, nuclear shapes and density distributions, and the impact of the pairing correlations on nuclear size will be discussed.
nucl-thnucl-exJ.Phys.G(2015)·205 citations
04
Chiral geometry in multiple chiral doublet bands
Hao Zhang · Qibo Chen
The chiral geometry of the multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters $γ$ in the particle rotor model with $π h_{11/2} \otimes ν h_{11/2}^{- 1}$ . The energy spectra, electromagnetic transition probabilities $B (M 1)$ and $B (E 2)$ , angular momenta, and $K$ -distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when $γ$ deviates from $3 0^{\circ}$ . The chiral geometry relies significantly on $γ$ , and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands.
nucl-thnucl-exCPC(2016)·14 citations
05
Investigation of the $nn Λ$ bound state in pionless effective theory
Shung-Ichi Ando🇰🇷 · Udit Raha🇮🇳 · Yongseok Oh🇰🇷
The possibility of an $nn Λ$ bound state is investigated in the framework of pionless effective field theory at leading order. A system of coupled integral equations are constructed in the spin-isospin basis, of which numerical solutions are investigated. In particular, we make use of the limit cycle behavior, i.e., cyclic singularities of coupled integral equations of the system, which would be associated with the formation of a three-body bound state, so-called the Efimov state, in the unitary limit. Furthermore, we find that, when the sharp momentum cutoff introduced in the integral equations is taken significantly larger than the hard scale of the effective theory, the coupling of a three-body contact interaction becomes cyclically singular indicating the onset of Efimov-like bound state formation. However, the paucity of empirical information to determine the parameters of the theory precludes a definitive conclusion on the existence of such a bound state. As a simple test of the feasibility of the $nn Λ$ bound system in nature, we explore the cutoff dependence of the theory, and uncertainties of the present study are discussed as well.
nucl-thhep-phPRC(2015)·34 citations
06
Appraising nuclear octupole moment contributions to the hyperfine structures in $^{211}$ Fr
B. K. Sahoo
Hyperfine structures of $^{211}$ Fr due to the interactions of magnetic dipole ( $μ$ ), electric quadrupole ( $Q$ ) and magnetic octupole ( $Ω$ ) moments with the electrons are investigated using the relativistic coupled-cluster (RCC) theory with an approximation of singles, doubles and important valence triples excitations in the perturbative approach. Validity of our calculations are substantiated by comparing the results with their available experimental values. Its $Q$ value has also been elevated by combining the measured hyperfine structure constant of the $7 p^{2} P_{3/2}$ state with our improved calculation. Considering the preliminary value of $Ω$ from the nuclear shell-model, its contributions to the hyperfine structures up to the $7 d^{2} D_{5/2}$ low-lying states in $^{211}$ Fr are estimated. Energy splittings of the hyperfine transitions in many states have been assessed to find out suitability to carry out their precise measurements so that $Ω$ of $^{211}$ Fr can be inferred from them unambiguously.
nucl-thphysics.atom-phPRA(2015)·5 citations
07
SU(6)-breaking symmetry and the ratio of proton momentum distributions
M.M. Giannini🇮🇹 · E. Santopinto🇮🇹 · A. Vassallo🇮🇹 · M. Vanderhaeghen🇩🇪
The ratio between the anomalous magnetic moments of proton and neutron has recently been suggested to be connected to the ratio of proton momentum fractions carried by valence quarks. This relation has been obtained within a parametrization of the Generalized Parton Distributions (GPD) \cite{gpv}, but it is completely independent of such a parametrization.\\ It will be shown that using different CQMs this relation holds within a few percent accuracy. This agreement is based on what all the CQMs have in common: the effective degrees of freedom of the three constituent quarks and the underlying SU(6) symmetry.\\ On the other hand, the experimental value of the ratio is not reproduced by CQMs. This means that the SU(6)-breaking mechanism contained in the phenomenological partonic distributions does not correspond to the SU(6) breaking mechanism implemented in the CQMs we have analyzed \cite{noi03}.\\ We will also show how this relation can be used in order to understand in which way to implement an $S U (6)$ -breaking mechanism and to test models.
nucl-th0 citations
08
The road to precision: Extraction of the specific shear viscosity of the quark-gluon plasma
Chun Shen🇺🇸 · Ulrich Heinz🇺🇸
Recent progress in extracting the specific shear viscosity of the Quark-Gluon Plasma from phenomenological studies is highlighted.
nucl-thhep-phnucl-exNucl.Phys.News(2015)·69 citations
09
Reply to comment on "Searching for Topological Defect Dark Matter via Nongravitational Signatures"
Y. V. Stadnik🇦🇺 · V. V. Flambaum🇦🇺
In the comment of Avelino, Sousa and Lobo [arXiv:1506.06028], it is argued, by comparing the kinetic energy of a topological defect with the overall energy of a pulsar, that the origin of the pulsar glitch phenomenon due to the passage of networks of topological defects through pulsars is faced with serious difficulties. Here, we point out that topological defects may trigger pulsar glitches within traditional scenarios, such as vortex unpinning. If the energy transfer from a topological defect exceeds the activation energy for a single pinned vortex, this may lead to an avalanche of unpinning of vortices and consequently a pulsar glitch, and therefore the source of angular momentum and energy required for a glitch event is provided by the pulsar itself. Indeed, the activation energy for such a process can be very small (essentially zero compared with the observed increase in the pulsar's rotational kinetic energy at the onset of a glitch). The unpinning of a vortex by a topological defect may occur through the passage of the defect into the core of the pulsar.
↳ hep-phastro-ph.COastro-ph.HEnucl-th+1PRL(2016)·4 citations
10
The Physics Of Supernova Neutrino Oscillations
James P. Kneller🇺🇸
On February 23, 1987 we collected 24 neutrinos from the explosion of a blue super-giant star in the Large Magellanic Cloud confirming the basic paradigm of core-collapse supernova. During the many years we have been waiting for a repeat of that momentous day, the number and size of neutrino detectors around the world has grown considerably. If the neutrinos from the next supernova in our Galaxy arrive tomorrow we shall collect upwards of tens of thousands of events and next generation detectors will increase the amount of data we collect by more than an order of magnitude. But it is also now apparent that the message is much more complex than previously thought because many time, energy and neutrino flavor dependent features are imprinted upon the signal either at emission or by the passage through the outer layers of the star. These features arise due to the explosion dynamics, the physics of nuclei at high temperatures and densities, and the properties of neutrinos. In this proceedings I will present some aspects of the physics of supernova neutrino oscillations and what we should expect to observe when the neutrinos from the next Galactic supernova (eventually) arrive.
↳ hep-phastro-ph.SRnucl-th0 citations
11
Magnetic response of energy levels of superconducting nanoparticles with spin-orbit scattering
Konstantin N. Nesterov · Y. Alhassid
Discrete energy levels of ultrasmall metallic grains are extracted in single-electron-tunneling-spectroscopy experiments. We study the response of these energy levels to an external magnetic field in the presence of both spin-orbit scattering and pairing correlations. In particular, we investigate $g$ -factors and level curvatures that parametrize, respectively, the linear and quadratic terms in the magnetic-field dependence of the many-particle energy levels of the grain. Both of these quantities exhibit level-to-level fluctuations in the presence of spin-orbit scattering. We show that the distribution of $g$ -factors is not affected by the pairing interaction and that the distribution of level curvatures is sensitive to pairing correlations even in the smallest grains in which the pairing gap is smaller than the mean single-particle level spacing. We propose the level curvature in a magnetic field as a tool to probe pairing correlations in tunneling spectroscopy experiments.
↳ cond-mat.mes-hallcond-mat.supr-connucl-thPRB(2015)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE