Nuclear Theory·nucl-th

Monday·June 18, 2018

7 papers—3 primary·4 cross-listed

01
[Submitted on 14 Jun 2018]
From Experimental Data to Pole Parameters in a Direct Way (Angle Dependent Continuum Ambiguity and Laurent + Pietarinen Expansion)
A. Švarc🇭🇷 · Y. Wunderlich🇩🇪 · H. Osmanović🇧🇦 · M. Hadžimehmedović🇧🇦 · R. Omerović🇧🇦 · J. Stahov🇧🇦 · V. Kashevarov🇩🇪 · K. Nikonov🇩🇪 · M. Ostrick🇩🇪 · L. Tiator🇩🇪 · R. Workman🇺🇸
Unconstrained partial-wave amplitudes obtained at discrete energies from fits to complete sets of eight independent observables which are required to uniquely reconstruct reaction amplitudes do not vary smoothly with energy, and are in principle non-unique. We demonstrate how this behavior can be ascribed to the continuum ambiguity. Starting from the spinless scattering case, we demonstrate how an unknown overall phase depending on energy and angle mixes the structures seen in the associated partial-wave amplitudes making the partial wave decomposition non-unique, and illustrate it on a simple toy model. We then apply these principles to pseudo-scalar meson photoproduction and show that the non-uniqueness effect can be removed through a phase rotation generating "up-to-a-phase" unique set of SE partial wave amplitudes. Extracting pole positions from partial wave amplitudes is the next step. Up to now, there was no reliable way to extract pole parameters from SE partial waves, but a new and simple single-channel method (Laurent + Pietarinen expansion) applicable for continuous and discrete data has been recently developed. It is based on applying the Laurent decomposition of partial wave amplitude, and expanding the nonresonant background into a power series of a conformal-mapping, quickly converging power series obtaining the simplest analytic function with well-defined partial wave analytic properties which fits the input. The generalization of this method to multi- channel case is also developed and presented. Unifying both methods in succession, one constructs a model independent procedure to extract pole parameters directly from experimental data without referring to any theoretical model.
Comments:
This article belongs to the Topical Collection "NSTAR2017 - The International Workshop on the Physics of Excited Nucleons". arXiv admin note: substantial text overlap with arXiv:1706.03211
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1806.05675 [pdf]
Few Body Syst.(2018)·5 citations
02
[Submitted on 14 Jun 2018]
Fusion cross-section for Ni-based reactions within the relativistic mean field formalism
M. Bhuyan · Raj Kumar
In this theoretical study, we establish an interrelationship between the nucleon-nucleon interaction potential and the nuclear fusion reaction cross-sections at low energies. The axially deformed self-consistent relativistic mean field with non-linear NL3 $^{*}$ force is used to calculate the density distribution of the projectile and target nuclei for fusion. The Wong formula is used to estimate the fusion cross-section and barrier distribution from the nucleus-nucleus optical potential for Ni-based systems, which are known for fusion hindrance phenomena. The results of the application of the so obtained nucleus-nucleus optical potential for the fusion cross-section from the recently developed relativistic $N N -$ interaction (R3Y) are compared with the well-known, phenomenological M3Y effective $N N$ potential. We found a relatively good results from R3Y interactions below the barrier energies as compare to the M3Y potential concerning the experimental data. We also observe the density dependence on the nuclear interaction potential in terms of nucleon-nucleon optical potentials.
Comments:
09 Pages, 09 Figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1806.05721 [pdf]
PRC(2018)·48 citations
03
[Submitted on 14 Jun 2018]
Pseudorapidity and initial energy densities in p+p and heavy ion collisions at RHIC and LHC
Z-F. Jiang🇨🇳 · M. Csanad🇭🇺 · G. Kasza🇭🇺 · C-B. Yang🇨🇳 · T. Csorgo🇭🇺
A known exact and accelerating solution of relativistic hydrodynamics for perfect fluids is utilized to describe pseudorapidity densities of $s_{N N} = 5.02$ TeV Pb $+$ Pb and $s = 13$ TeV $p$ $+$ $p$ collisions at LHC. We evaluate a conjectured initial energy densities $ϵ_{corr}$ in these collisions, and compare them to Bjorken's initial energy density estimates, and to results for Pb $+$ Pb collisions at $s_{N N} = 2.76$ TeV and $p$ $+$ $p$ collisions at $s = 7$ and 8 TeV.
Comments:
6 pages, 2 figures. Presented at the XIII Workshop on Particle Correlations and Femtoscopy, Cracow, Poland
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1806.05750 [pdf]
Acta Phys. Pol. B Proc. Suppl. vol. 12 (2…·12 citations
04
[Submitted on 15 Jun 2018] (cross-list from hep-th)
Kubo formulas for thermodynamic transport coefficients
Pavel Kovtun🇨🇦 · Ashish Shukla🇨🇦
Uncharged relativistic fluids in 3+1 dimensions have three independent thermodynamic transport coefficients at second order in the derivative expansion. Fluids with a single global $U (1)$ current have nine, out of which seven are parity preserving. We derive the Kubo formulas for all nine thermodynamic transport coefficients in terms of equilibrium correlation functions of the energy-momentum tensor and the current. All parity-preserving coefficients can be expressed in terms of two-point functions in flat space without external sources, while the parity-violating coefficients require three-point functions. We use the Kubo formulas to compute the thermodynamic coefficients in several examples of free field theories.
Comments:
v1: 21 pages, 1 figure; v2: footnotes added, version published in JHEP
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1806.05774 [pdf]
JHEP(2018)·43 citations
05
[Submitted on 15 Jun 2018] (cross-list from hep-ph)
Centrality dependence of kinetic freeze-out temperature and transverse flow velocity in high energy nuclear collisions
Muhammad Waqas🇨🇳 · Fu-Hu Liu🇨🇳
Centrality-dependent double-differential transverse momentum spectra of charged pions, kaons, and (anti)protons produced in mid-pseudorapidity interval in $s_{N N} = 200$ GeV gold-gold and deuteron-gold collisions with different centralities are analyzed by the blast-wave model with Boltzmann-Gibbs statistics. Meanwhile, the mentioned spectra in mid-rapidity interval in $s_{N N} = 2.76$ TeV lead-lead and $s_{N N} = 5.02$ TeV proton-lead collisions with different centralities are analyzed by the same model. The model results are approximately in agreement with the experimental data in special transverse momentum ranges. It is shown that with the increase of event centrality and energy, the kinetic freeze-out temperature of the emission source and the transverse flow velocity of the produced particles slightly increase in some cases but they do not give an obvious change in other cases. Meanwhile, the kinetic freeze-out temperature (transverse flow velocity) increases (decreases) with the increase of particle mass. The average transverse momentum and initial temperature increase with the increase of event centrality, collision energy, and particle mass. This work also confirms the maximum size dependent effect, which states that the main parameters such as the kinetic freeze-out temperature and transverse flow velocity are mainly determined by the heaviest nucleus from proton-nucleus to nucleus-nucleus collisions.
Comments:
18 pages, 6 figures. Indian Journal of Physics, accepted
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1806.05863 [pdf]
Indian J.Phys.(2022)·26 citations
06
[Submitted on 14 Jun 2018] (cross-list from nucl-ex)
Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in $^{90, 92}$ Zr and $^{92}$ Mo
Y. K. Gupta · K. B. Howard · U. Garg · J. T. Matta · M. Senyigit · M. Itoh · S. Ando · T. Aoki · A. Uchiyama · S. Adachi · M. Fujiwara · C. Iwamoto and 10 other authors
The isoscalar giant monopole, dipole, and quadrupole strength distributions have been deduced in $^{90, 92}$ Zr, and $^{92}$ Mo from "background-free" spectra of inelastic $α$ -particle scattering at a beam energy of 385 MeV at extremely forward angles, including 0 $^{\circ}$ . These strength distributions were extracted by a multipole-decomposition analysis based on the expected angular distributions of the respective multipoles. All these strength distributions for the three nuclei practically coincide with each other, affirming that giant resonances, being collective phenomena, are not influenced by nuclear shell structure near $A \sim$ 90, contrary to the claim in a recent measurement.
Comments:
12 pages, 12 figures; Accepted for publication in Phys. Rev. C. arXiv admin note: text overlap with arXiv:1607.02198
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1806.05980 [pdf]
PRC(2018)·30 citations
07
[Submitted on 15 Jun 2018] (cross-list from hep-ph)
Short-Range Neutrinoless Double Beta Decay Mechanisms
Lukas Graf🇬🇧 · Frank F. Deppisch🇬🇧 · Francesco Iachello🇺🇸 · Jenni Kotila🇫🇮
Neutrinoless double beta decay can significantly help to shed light on the issue of non-zero neutrino mass, as observation of this lepton number violating process would imply neutrinos are Majorana particles. However, the underlying interaction does not have to be as simple as the standard neutrino mass mechanism. The entire variety of neutrinoless double beta decay mechanisms can be approached effectively. In this work we focus on a theoretical description of short-range effective contributions to neutrinoless double beta decay, which are equivalent to 9-dimensional effective operators incorporating the appropriate field content. We give a detailed derivation of the nuclear matrix elements and phase space factors corresponding to individual terms of the effective Lagrangian. Using these, we provide general formulae for the neutrinoless double beta decay half-life and angular correlation of the outgoing electrons.
Comments:
42 pages, 9 figures, added discussion of QCD running and decay distributions
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1806.06058 [pdf]
PRD(2018)·73 citations

Affiliations

first authorsco-authorsvia INSPIRE

From Experimental Data to Pole Parameters in a Direct Way (Angle Dependent Continuum Ambiguity and Laurent + Pietarinen Expansion)

Fusion cross-section for Ni-based reactions within the relativistic mean field formalism

Pseudorapidity and initial energy densities in p+p and heavy ion collisions at RHIC and LHC

Kubo formulas for thermodynamic transport coefficients

Centrality dependence of kinetic freeze-out temperature and transverse flow velocity in high energy nuclear collisions

Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in 90,92Zr and 92Mo

Short-Range Neutrinoless Double Beta Decay Mechanisms

Affiliations

Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in $^{90, 92}$ Zr and $^{92}$ Mo