Nuclear Theory·nucl-th

Wednesday·June 22, 2016

12 papers—5 primary·7 cross-listed

01
[Submitted on 13 Jun 2016]
Landscape of atomic nuclear shapes
Chang-Bum Moon
We exhibit a wide variety of the nuclear shape phases over the nuclear chart along with a shell model scheme. Various nuclear shapes are demonstrated within the framework of proton-neutron spin-orbital interactions; ferro-deformed, sub-ferro-deformed, and spherical shapes. The spherical shape is classified into the three magic-number categories in view of a large shell gap mechanism; double-magic nuclei I, double magic nuclei II, and double magic nuclei III. We discuss nuclear shape coexistence in the space Z = 76 to 84 as providing a new way to understanding the dynamical shape phases.
Comments:
8 pages, 5 figures, Keywords: double-magic nuclei I, double-magic nuclei II, double-magic nuclei III, ferro-deformation, sub-ferro-deformation, reinforced double-shell closures, sub-reinforced double-shell closures, pseudo-(sub)shell, shape phase transitions, shape coexistence
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.06302 [pdf]
0 citations
02
[Submitted on 20 Jun 2016]
Local chiral potentials and the structure of light nuclei
Maria Piarulli🇺🇸 · Luca Girlanda🇮🇹 · Rocco Schiavilla🇺🇸 · Alejandro Kievsky🇮🇹 · Alessandro Lovato🇺🇸 · Laura E. Marcucci🇮🇹 · Steven C. Pieper🇺🇸 · Michele Viviani🇮🇹 · Robert B. Wiringa🇺🇸
We present fully local versions of the minimally non-local nucleon-nucleon potentials constructed in a previous paper [M.\ Piarulli {\it et al.}, Phys.\ Rev.\ C {\bf 91}, 024003 (2015)], and use them in hypersperical-harmonics and quantum Monte Carlo calculations of ground and excited states of $^{3}$ H, $^{3}$ He, $^{4}$ He, $^{6}$ He, and $^{6}$ Li nuclei. The long-range part of these local potentials includes one- and two-pion exchange contributions without and with $Δ$ -isobars in the intermediate states up to order $Q^{3}$ ( $Q$ denotes generically the low momentum scale) in the chiral expansion, while the short-range part consists of contact interactions up to order $Q^{4}$ . The low-energy constants multiplying these contact interactions are fitted to the 2013 Granada database in two different ranges of laboratory energies, either 0--125 MeV or 0--200 MeV, and to the deuteron binding energy and $nn$ singlet scattering length. Fits to these data are performed for three models characterized by long- and short-range cutoffs, $R_{L}$ and $R_{S}$ respectively, ranging from $(R_{L}, R_{S}) = (1.2, 0.8)$ fm down to $(0.8, 0.6)$ fm. The long-range (short-range) cutoff regularizes the one- and two-pion exchange (contact) part of the potential.
Comments:
29 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.06335 [pdf]
PRC(2016)·183 citations
03
[Submitted on 21 Jun 2016]
Emission of neutron-proton and proton-proton pairs in electron scattering induced by meson-exchange currents
I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · A. De Pace🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸
We use a relativistic model of meson-exchange currents to compute the proton-neutron and proton-proton yields in $(e, e^{'})$ scattering from $^{12}$ C in the 2p-2h channel. We compute the response functions and cross section with the relativistic Fermi gas model for a range of kinematics from intermediate to high momentum transfers. We find a large contribution of neutron-proton configurations in the initial state, as compared to proton-proton pairs. The different emission probabilities of distinct species of nucleon pairs are produced in our model only by meson-exchange currents, mainly by the $Δ$ isobar current. We also analyze the effect of the exchange contribution and show that the direct/exchange interference strongly affects the determination of the np/pp ratio.
Comments:
5 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1606.06480 [pdf]
PRC(2016)·15 citations
04
[Submitted on 21 Jun 2016]
Mass dependence and isospin dependence of short-range correlated pairs
U. Mosel🇩🇪 · K. Gallmeister🇩🇪
The target-mass number dependence of nucleon-nucleon pairs with short-range correlations is explored in a physically transparent geometrical model within a zero-range approximation. The observed $A$ dependence of 2-nucleon ejection cross sections in $(e, e^{'})$ reactions is found to reflect the mass dependence of nuclear density distributions. A parametrization of this $A$ dependence is given. The $A$ dependence of proton-proton vs.\ proton-neutron pairs relative to $^{12}$ C is also analyzed in this model. It can be understood using simple combinatorics without any additional isospin dependence.
Comments:
Version as accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1606.06499 [pdf]
PRC(2016)·12 citations
05
[Submitted on 21 Jun 2016]
Particle production and equilibrium properties within a new hadron transport approach for heavy-ion collisions
J. Weil🇩🇪 · V. Steinberg🇩🇪 · J. Staudenmaier🇩🇪 · L.G. Pang🇩🇪 · D. Oliinychenko🇩🇪 · J. Mohs🇩🇪 · M. Kretz🇩🇪 · T. Kehrenberg🇩🇪 · A. Goldschmidt🇩🇪 · B. Bäuchle🇩🇪 · J. Auvinen🇩🇪 · M. Attems🇩🇪 · H. Petersen🇩🇪
The microscopic description of heavy-ion reactions at low beam energies is achieved within hadronic transport approaches. In this article a new approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced and applied to study the production of non-strange particles in heavy-ion reactions at $E_{kin} = 0.4 - 2 A$ GeV. First, the model is described including details about the collision criterion, the initial conditions and the resonance formation and decays. To validate the approach, equilibrium properties such as detailed balance are presented and the results are compared to experimental data for elementary cross sections. Finally results for pion and proton production in C+C and Au+Au collisions is confronted with HADES and FOPI data. Predictions for particle production in $π + A$ collisions are made.
Comments:
30 pages, 30 figures, replaced with published version; only minor changes
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1606.06642 [pdf]
PRC(2016)·454 citations
06
[Submitted on 18 Jun 2016] (cross-list from quant-ph)
Decoherence in Sub-Systems of an Isolated System and the Disappearance of Quantum Multiverse
Takuji Ishikawa
This study was started to know mysterious classicality of nuclei. Using three particles model without external environments, it is found that decisions of respective state of three particles by decoherence are not simultaneous. Furthermore, in this model, wave function of total three body system collapses spontaneously without any external environments. Therefore we may able to insist that a wavefunction of our universe has already collapsed spontaneously without any external observer, because of the same mechanism with this model.
Subjects:
Quantum Physics (quant-ph); Nuclear Theory (nucl-th)
arXiv:
1606.06282 [pdf]
0 citations
07
[Submitted on 20 Jun 2016] (cross-list from hep-ph)
High Resolution Nonperturbative Light-Front Simulations of the True Muonium Atom
Henry Lamm🇺🇸 · Richard Lebed🇺🇸
Through the development of a parallel code called TMSWIFT, an extensive light-front quantization study of the nonperturbative spectrum of the bound state $(μ^{+} μ^{-})$ , true muonium, has been performed. Using Padé approximants, it has been possible to extract continuum and infinite-cutoff limits for the singlet and triplet states for a range of values of the coupling constant $α$ . This data set allows for an investigation of the $α$ dependence of the light-front spectra, the results of which are compared to standard calculations. Decay constants have also been obtained. Improved calculations have been undertaken for the energy shifts due to the presence of a second, lighter flavor ( $e$ ). Finally, initial results for three-flavor ( $e$ , $μ$ , $τ$ ) calculations are presented.
Comments:
12 pages, 5 figures, Matches PRD version except for additional references
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
1606.06358 [pdf]
PRD(2016)·7 citations
08
[Submitted on 21 Jun 2016] (cross-list from hep-ph)
Correlations of conserved number mixed susceptibilities in a hadron resonance gas model
D. K. Mishra🇮🇳 · P. K. Netrakanti🇮🇳 · Bedangadas Mohanty🇮🇳
The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum ( $p_{T}$ ) and pseudorapidity ( $η$ ), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of $p_{T}$ and $η$ acceptance on the ratio of the susceptibilities are small relative to their dependence on the beam energy or the charged states of the used particles. We also present a HRG based calculation for various combinations of cumulant ratios of protons and pions, recently proposed as robust observables (with no theoretical uncertainties) for critical point search in the experiments. These results which increase as a function of collision energy will provide a better baseline for non-critical point physics compared to Poisson expectation.
Comments:
8 pages, 8 figures; Two new figures added with minor text modification, published in Physical Rev. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1606.06538 [pdf]
PRC(2016)·6 citations
09
[Submitted on 21 Jun 2016] (cross-list from hep-ph)
Flavor-dependent eigenvolume interactions in a hadron resonance gas
P. Alba🇩🇪 · V. Vovchenko🇩🇪 · M. I. Gorenstein🇺🇦 · H. Stoecker🇩🇪
Eigenvolume effects in the hadron resonance gas (HRG) model are studied for experimental hadronic yields in nucleus-nucleus collisions. If particle eigenvolumes are different for different hadron species, the excluded volume HRG (EV-HRG) improves fits to multiplicity data. In particular, using different mass~-~volume relations for strange and non-strange hadrons we observe a remarkable improvement in the quality of the fits. This effect appears to be rather insensitive to other details in the schemes employed in the EV-HRG. We show that the parameters found from fitting the data of the ALICE Collaboration in central Pb+Pb collisions at the collision energy $s_{NN} = 2.76$ ~TeV entail the same improvement for all centralities at the same collision energy, and for the RHIC and SPS data at lower collision energies. Our findings are put in the context of recent fits of lattice QCD results.
Comments:
4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.06542 [pdf]
NPA(2018)·57 citations
10
[Submitted on 21 Jun 2016] (cross-list from hep-th)
A local and renormalizable framework for the gauge-invariant operator $A_{m i n}^{2}$ in Euclidean Yang-Mills theories in linear covariant gauges
M. A. L. Capri🇧🇷 · D. Fiorentini🇧🇷 · M. S. Guimaraes🇧🇷 · B. W. Mintz🇧🇷 · L. F. Palhares🇧🇷 · S. P. Sorella🇧🇷
We address the issue of the renormalizability of the gauge-invariant non-local dimension-two operator $A_{min}^{2}$ , whose minimization is defined along the gauge orbit. Despite its non-local character, we show that the operator $A_{min}^{2}$ can be cast in local form through the introduction of an auxiliary Stueckelberg field. The localization procedure gives rise to an unconventional kind of Stueckelberg-type action which turns out to be renormalizable to all orders of perturbation theory. In particular, as a consequence of its gauge invariance, the anomalous dimension of the operator $A_{min}^{2}$ turns out to be independent from the gauge parameter $α$ entering the gauge-fixing condition, being thus given by the anomalous dimension of the operator $A^{2}$ in the Landau gauge.
Comments:
35 pages; v2: ref. added
Subjects:
High Energy Physics — Theory (hep-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1606.06601 [pdf]
PRD(2016)·40 citations
11
[Submitted on 21 Jun 2016] (cross-list from hep-ph)
$P$ -wave coupled-channel scattering of $B_{s} π, B_{s}^{*} π, B K, B^{*} K$ and the puzzling $X (5568)$
Xian-Wei Kang🇪🇸 · J. A. Oller🇪🇸
The D0 Collaboration has recently reported a narrow peak structure in the $B_{s}^{0} π^{\pm}$ invariant-mass spectrum, that is called $X (5568)$ . Its proposed quantum numbers $J^{P} = 0^{+} / 1^{+}$ are not determined unambiguously, and we show that one can fit the data assuming $J^{P} = 1^{-}$ with the same mass and width for the resonance signal. The corresponding isovector $P$ -wave coupled-channel scattering involving the states $B_{s} π$ , $B_{s}^{*} π$ , $B K$ and $B^{*} K$ is studied employing leading-order Heavy Meson Chiral Perturbation Theory, which is then unitarized making use of standard techniques from Unitary Chiral Perturbation Theory. The subtraction constants that appear in the unitarization process are determined by a $u$ -channel crossing symmetry constraint or by naturalness arguments, being the numerical values obtained in both cases quite closed, and no further freedom is left in the model. A crucial point is that if the $X (5568)$ is $1^{-}$ and decaying into $B_{s}^{0} π^{\pm}$ then it should appear as a pole in the $T$ -matrix elements. It finally turns out that no $X (5568)$ pole is found that can be qualified as dynamically generated from the isovector $P$ -wave coupled-channel dynamics. This result disfavors the interpretation of the $X (5568)$ within a "molecular" picture.
Comments:
10 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1606.06665 [pdf]
PRD(2016)·44 citations
12
[Submitted on 21 Jun 2016] (cross-list from hep-ph)
Big Bang Nucleosynthesis in the presence of sterile neutrinos with altered dispersion relations
Elke Aeikens🇦🇹 · Heinrich Päs🇩🇪 · Sandip Pakvasa🇺🇸 · Thomas J. Weiler🇺🇸
Big Bang Nucleosynthesis imposes stringent bounds on light sterile neutrinos mixing with the active flavors. Here we discuss how altered dispersion relations can weaken such bounds and allow compatibility of new sterile neutrino degrees of freedom with a successful generation of the light elements in the early Universe.
Comments:
15 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
arXiv:
1606.06695 [pdf]
PRD(2016)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE