Nuclear Theory·nucl-th

Tuesday·October 13, 2015

21 papers—10 primary·11 cross-listed

01
[Submitted on 9 Oct 2015]
Structure of the neutral pion and its electromagnetic transition form factor
K. Raya🇲🇽 · L. Chang🇨🇳 · A. Bashir🇲🇽 · J. J. Cobos-Martinez🇲🇽 · L. X. Gutiérrez-Guerrero🇲🇽 · C. D. Roberts🇺🇸 · P. C. Tandy🇺🇸
The $γ^{*} γ \to π^{0}$ transition form factor, $G (Q^{2})$ , is computed on the entire domain of spacelike momenta using a continuum approach to the two valence-body bound-state problem in relativistic quantum field theory: the result agrees with data obtained by the CELLO, CLEO and Belle Collaborations. The analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor, and demonstrates, too, that a fully self-consistent treatment can readily connect a pion PDA that is a broad, concave function at the hadronic scale with the perturbative QCD prediction for the transition form factor in the hard photon limit. The normalisation of that limit is set by the scale of dynamical chiral symmetry breaking, which is a crucial feature of the Standard Model. Understanding of the latter will thus remain incomplete until definitive transition form factor data is available on $Q^{2} > 10$ GeV $^{2}$ .
Comments:
9 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1510.02799 [pdf]
PRD(2016)·131 citations
02
[Submitted on 10 Oct 2015]
Structure effects in the $^{15}$ N( $n, γ$ ) $^{16}$ N radiative capture reaction from the Coulomb dissociation of $^{16}$ N
Neelam (IIT-R) · Shubhchintak (TAMU-C) · R. Chatterjee (IIT-R)
Purpose : The aim of this paper is to calculate the $^{15}$ N( $n, γ$ ) $^{16}$ N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of $^{16}$ N to the cross section. Method : A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of $^{16}$ N on Pb at 100 MeV/u. This is then related to the photodisintegration cross section of $^{16}$ N( $γ, n$ ) $^{15}$ N and subsequently invoking the principle of detailed balance, the $^{15}$ N( $n, γ$ ) $^{16}$ N capture cross section is calculated. Results : The non-resonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seems to favor a more single particle nature for the low-lying states of $^{16}$ N. The total neutron capture rate is also calculated by summing up non-resonant and resonant (significant only at temperatures greater than 1 GK) contributions and comparison is made with other charged particle capture rates. In the typical temperature range of $0.1 - 1.2$ GK, almost all the contribution to the reaction rate comes from capture cross sections below 0.25 MeV. Conclusion : We have attempted to resolve the discrepancy in the spectroscopic factors of low-lying $^{16}$ N levels and conclude that it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture cross section for the reaction, especially below 0.25 MeV.
Comments:
8 pages, 8 figures, To be published in Phy. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.02897 [pdf]
PRC(2015)·19 citations
03
[Submitted on 11 Oct 2015]
Resonances and Reactions from Mean-Field Dynamics
P. D. Stevenson
The time-dependent version of nuclear density functional theory, using functionals derived from Skyrme interactions, is able to approximately describe nuclear dynamics. We present time-dependent results of calculations of dipole resonances, concentrating on excitations of valence neutrons against a proton plus neutron core in the neutron-rich doubly-magic $^{132}$ Sn nucleus, and results of collision dynamics, highlighting potential routes to ternary fusion, with the example of a collision of $^{48}$ Ca+ $^{48}$ Ca+ $^{208}$ Pb resulting in a compound nucleus of element 120 stable against immiedate fission
Comments:
6 pages, 4 figures, submitted to proceedings of NSRT15 conference, Dubna, Russia
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.03017 [pdf]
EPJ Web Conf.(2016)·0 citations
04
[Submitted on 11 Oct 2015]
New Signals of Quark-Gluon-Hadron Mixed Phase Formation
K.A. Bugaev🇺🇦 · V.V. Sagun🇺🇦 · A.I. Ivanytskyi🇺🇦 · D.R. Oliinychenko🇺🇦 · E.-M. Ilgenfritz🇷🇺 · E.G. Nikonov🇷🇺 · A.V. Taranenko🇷🇺 · G.M. Zinovjev🇺🇦
Here we present several remarkable irregularities at chemical freeze-out which are found using an advanced version of the hadron resonance gas model. The most prominent of them are the sharp peak of the trace anomaly existing at chemical freeze-out at the center of mass energy 4.9 GeV and two sets of highly correlated quasi-plateaus in the collision energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon which we found at the center of mass energies 3.8-4.9 GeV and 7.6-10 GeV. The low energy set of quasi-plateaus was predicted a long time ago. On the basis of the generalized shock-adiabat model we demonstrate that the low energy correlated quasi-plateaus give evidence for the anomalous thermodynamic properties inside the quark-gluon-hadron mixed phase. It is also shown that the trace anomaly sharp peak at chemical freeze-out corresponds to the trace anomaly peak at the boundary between the mixed phase and quark gluon plasma. We argue that the high energy correlated quasi-plateaus may correspond to a second phase transition and discuss its possible origin and location. Besides we suggest two new observables which may serve as clear signals of these phase transformations.
Comments:
14 pages, 4 figures, new signals of QGP formation are suggested
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.03099 [pdf]
EPJA(2016)·13 citations
05
[Submitted on 12 Oct 2015]
Global performance of multireference density functional theory for low-lying states in $s d$ -shell nuclei
Xian-Ye Wu🇨🇳 · Xian-Rong Zhou🇨🇳
We present a comprehensive study of low-lying states in even-even Ne, Mg, Si, S, Ar isotopes with the multireference density functional theory (MR-DFT) based on a relativistic point-coupling energy density functional (EDF). Beyond mean-field (BMF) effects are taken into account by configuration mixing of both particle-number and angular-momentum projected axially deformed states with generator coordinate method (GCM). Global performance of the MR-DFT for the properties of both ground state and of the first $2^{+}, 4^{+}$ states is examined, in comparison with previous studies based on nonrelativistic EDFs and available data. Our results indicate that an EDF parameterized at the BMF level is demanded to achieve a quantitative description.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.03127 [pdf]
PRC(2015)·8 citations
06
[Submitted on 12 Oct 2015]
Multiplicity fluctuations in heavy-ion collisions using canonical and grand-canonical ensemble
P. Garg🇮🇳 · D. K. Mishra🇮🇳 · P. K. Netrakanti🇮🇳 · A. K. Mohanty🇮🇳
We report the higher order cumulants and their ratios for baryon, charge and strangeness multiplicity in canonical and grand-canonical ensembles in ideal thermal model including all the resonances. When the number of conserved quanta is small, an explicit treatment of these conserved charges is required, which leads to a canonical description of the system and the fluctuations are significantly different from the grand canonical ensemble. Cumulant ratios of total charge and net-charge multiplicity as a function of collision energies are also compared in grand canonical ensemble.
Comments:
7 pages, 5 Figs, Published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1510.03158 [pdf]
EPJA(2016)·3 citations
07
[Submitted on 12 Oct 2015]
Continuum discretized BCS approach for weakly bound nuclei
J. A. Lay · C. E. Alonso · L. Fortunato · A. Vitturi
The Bardeen-Cooper-Schrieffer (BCS) formalism is extended by including the single-particle continuum in order to analyse the evolution of pairing in an isotopic chain from stability up to the drip line. We propose a continuum discretized generalized BCS based on single-particle pseudostates (PS). These PS are generated from the diagonalization of the single-particle Hamiltonian within a Transformed Harmonic Oscillator (THO) basis. The consistency of the results versus the size of the basis is studied. The method is applied to neutron rich Oxygen and Carbon isotopes and compared with similar previous works and available experimental data. We make use of the flexibility of the proposed model in order to study the evolution of the occupation of the low-energy continuum when the system becomes weakly bound. We find a larger influence of the non-resonant continuum as long as the Fermi level approaches zero.
Comments:
20 pages, 16 figures, to be submitted
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1510.03185 [pdf]
J.Phys.G(2016)·5 citations
08
[Submitted on 12 Oct 2015]
The long and winding road from chiral effective Lagrangians to nuclear structure
Ulf-G Meißner🇩🇪
I review the chiral dynamics of nuclear physics. In the first part, I discuss the new developments in the construction of the forces between two, three and four nucleons which have been partly carried out to fifth order in the chiral expansion. It is also shown that based on these forces in conjunction with the estimation of the corresponding theoretical uncertainties, the need for three-nucleon forces in few nucleon systems can be unambiguously established. I also introduce the lattice formulation of these forces, which allow for truly ab initio calculations of nuclear structure and reactions. I present some pertinent results of the nuclear lattice approach. Finally, I discuss how few-nucleon systems and nuclei can be used to explore symmetries and physics within and beyond the Standard Model.
Comments:
commissioned article for a Special Physica Scripta Edition commemorating the 40-year Anniversary of the Nobel Prize for A. Bohr, B. Mottelson and L. Rainwater
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1510.03230 [pdf]
Phys.Scripta(2016)·37 citations
09
[Submitted on 12 Oct 2015]
Isospin effects in N~Z nuclei in extended Density Functional Theory
Wojciech Satula🇵🇱 · Witold Nazarewicz🇵🇱
This paper overviews various phenomena related to the concept of isospin symmetry. The focus is on N~Z nuclei, which are excellent laboratories of isospin physics. The theoretical framework applied is nuclear Density Functional Theory and its isospin- and angular-momentum projected extensions, as well as symmetry-projected multi-reference models. The topics covered include: isospin impurities, superallowed beta decays, beta-transitions in mirror nuclei, isospin breaking hadronic interactions, mirror and triplet binding energy differences, and isoscalar pairing.
Comments:
submitted to Physica Scripta to the Focus Issue on Nuclear Structure: Celberating the 75 Nobel Prize
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1510.03251 [pdf]
Phys.Scripta(2016)·15 citations
10
[Submitted on 12 Oct 2015]
Evidence for the virtual beta-gamma transition in 59Ni
M. Pfützner · K. Pachucki · J. Żylicz
A novel theory of radiative electron capture in second forbidden non-unique transition, is applied to reanalyze experimental data obtained previously for the decay of 59Ni. The measured gamma spectrum is shown to be distorted at the high-energy end, presenting the first direct evidence for the virtual beta-gamma transition through the excited state in 59Co. The complete theoretical predictions, including both the direct and the virtual decay channels, as well as the interference between them, reproduce very well the experimental spectrum. The virtual nuclear component amounts to about 4% of the total gamma intensity.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1510.03310 [pdf]
PRC(2015)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE