Nuclear Theory·nucl-th

Thursday·February 5, 2015

10 papers—5 primary·5 cross-listed

01
[Submitted on 4 Feb 2015]
Emergence of rotational bands in ab initio no-core configuration interaction calculations
M. A. Caprio · P. Maris · J. P. Vary · R. Smith
Rotational bands have been observed to emerge in ab initio no-core configuration interaction (NCCI) calculations for p-shell nuclei, as evidenced by rotational patterns for excitation energies, electromagnetic moments, and electromagnetic transitions. We investigate the ab initio emergence of nuclear rotation in the Be isotopes, focusing on 9Be for illustration, and make use of basis extrapolation methods to obtain ab initio predictions of rotational band parameters for comparison with experiment. We find robust signatures for rotational motion, which reproduce both qualitative and quantitative features of the experimentally observed bands.
Comments:
10 pages, 5 figures; presented at Advanced Many-Body and Statistical Methods in Mesoscopic Systems II, Brasov, Romania, September 1-5, 2014; submitted to Rom. J. Phys
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.01083 [pdf]
Rom.J.Phys.(2015)·4 citations
02
[Submitted on 4 Feb 2015]
Nucleus-nucleus potential with shell-correction contribution
V. Yu. Denisov
The full relaxed-density potential between spherical nuclei is considered as a sum of the macroscopic and shell-correction contributions. The macroscopic part of the potential is related to a nucleus-nucleus potential obtained in the framework of the extended Thomas-Fermi approach with the Skyrme and Coulomb forces and the relaxed-density ansatz for evaluation of proton and neutron densities of interacting nuclei. A simple prescription for the shell-correction part of the total potential is discussed. The parameters of the shell-correction and macroscopic parts of the relaxed-density potential are found by fitting the empirical barrier heights of the 89 nucleus-nucleus systems as well as macroscopic potentials evaluated for 1485 nucleus-nucleus systems at 12 distances around touching points.
Comments:
11 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.01164 [pdf]
PRC(2015)·33 citations
03
[Submitted on 4 Feb 2015]
Reconstructing the final state of Pb+Pb collisions at $s_{N N} = 2.76$ TeV
Ivan Melo🇸🇰 · Boris Tomasik🇸🇰
We fit the single-hadron transverse-momentum spectra measured in Pb+Pb collisions at $s_{N N} = 2.76$ TeV with the blast-wave model that includes production via resonance decays. Common fit to pions, kaons, (anti)protons, and lambdas yields centrality dependence of the freeze-out temperature and transverse expansion velocity. In the most central collisions we see $T = 98$ MeV and $⟨ v_{t} ⟩ = 0.654$ . The $K^{*}$ resonance fits into this picture but the $ϕ$ meson might freeze-out a little earlier. Multistrange baryons seem to decouple at higher temperature and weaker transverse flow. Within our model we observe hints of chemical potential for the charged pions.
Comments:
accepted version (some explanations added with respect to v1), 21 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1502.01247 [pdf]
J.Phys.G(2016)·31 citations
04
[Submitted on 4 Feb 2015]
Comparative study of three-nucleon force models in nuclear matter
Domenico Logoteta · Isaac Vidaña · Ignazio Bombaci · Alejandro Kievsky
We calculate the energy per particle of symmetric nuclear matter and pure neutron matter using the microscopic many-body Brueckner-Hartree-Fock (BHF) approach and employing the Argonne V18 (AV18) nucleon-nucleon (NN) potential supplemented with two different three-nucleon force models recently constructed to reproduce the binding energy of $^{3}$ H, $^{3}$ He and $^{4}$ He nuclei as well as the neutron-deuteron doublet scattering length. We find that none of these new three-nucleon force models is able to reproduce simultaneously the empirical saturation point of symmetric nuclear matter and the properties of three- and four-nucleon systems.
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1502.01248 [pdf]
PRC(2015)·34 citations
05
[Submitted on 4 Feb 2015]
Amplitude extraction in pseudoscalar-meson photoproduction: towards a situation of complete information
Jannes Nys🇧🇪 · Tom Vrancx🇧🇪 · Jan Ryckebusch🇧🇪
A complete set for pseudoscalar-meson photoproduction is a minimum set of observables from which one can determine the underlying reaction amplitudes unambiguously. The complete sets considered in this work involve single- and double-polarization observables. It is argued that for extracting amplitudes from data, the transversity representation of the reaction amplitudes offers advantages over alternate representations. It is shown that with the available single-polarization data for the p({\gamma},K^+)\Lambda reaction, the energy and angular dependence of the moduli of the normalized transversity amplitudes in the resonance region can be determined to a fair accuracy. Determining the relative phases of the amplitudes from double-polarization observables is far less evident.
Comments:
Accepted in JPhysG; Focus issue "Enhancing the interaction between nuclear experiment and theory through information and statistics" (ISNET)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1502.01259 [pdf]
J.Phys.G(2015)·14 citations
06
[Submitted on 30 Jan 2015] (cross-list from hep-ph)
Neutrino induced decoherence and variation in nuclear decay rates
Douglas Singleton🇺🇸 · Nader Inan🇺🇸 · Raymond Y. Chiao🇺🇸
Recent work has proposed that the interaction between ordinary matter and a stochastic gravitational background can lead to the decoherence of large aggregates of ordinary matter. In this work we point out that these arguments can be carried over to a stochastic neutrino background but with the Planck scale of the gravitational decoherence replaced by the weak scale. This implies that it might be possible to observe such neutrino induced decoherence on a small, microscopic system rather than a macroscopic system as is the case for gravitationally induced decoherence. In particular we suggest that neutrino decoherence could be linked with observed variations in the decay rates of certain nuclei. Finally we point out that this proposed neutrino induced decoherence can be considered the complement of the Mikheev-Smirnov-Wolfenstein (MSW) effect.
Comments:
15 pages revtex, 0 figures, to be published Phys. Lett. A
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1501.07665 [pdf]
PLA(2015)·4 citations
07
[Submitted on 3 Feb 2015] (cross-list from hep-ph)
Analysis of pPb collisions at LHC energies in the relativistic diffusion model
P. Schulz🇩🇪 · G. Wolschin🇩🇪
Particle production sources in pPb collisions at LHC energies are investigated in pseudorapidity space as functions of centrality. The nonequilibrium-statistical relativistic diffusion model (RDM) with three sources is applied to the analysis of preliminary charged-hadron distributions measured by the ATLAS and ALICE collaborations in pPb collisions at 5.02 TeV. The size of the midrapidity source relative to the fragmentation sources in pPb collisions is considered as function of centrality, and incident energy. At LHC energies particle production from the mid-rapidity gluon-gluon source is larger than that from the fragmentation sources at all centralities. Conclusions regarding the statistical equilibration process are drawn.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.01056 [pdf]
EPJA(2015)·6 citations
08
[Submitted on 4 Feb 2015] (cross-list from hep-th)
The Light-Front Vacuum
Marc Herrmann🇺🇸 · Wayne Polyzou🇺🇸
Background: The vacuum in the light-front representation of quantum field theory is trivial while vacuum in the equivalent canonical representation of the same theory is non-trivial. Purpose: Understand the relation between the vacuum in light-front and canonical representations of quantum field theory and the role of zero-modes in this relation. Method: Vacuua are defined as linear functionals on an algebra of field operators. The role of the algebra in the definition of the vacuum is exploited to understand this relation. Results: The vacuum functional can be extended from the light-front Fock algebra to an algebra of local observables. The extension to the algebra of local observables is responsible for the inequivalence. The extension defines a unitary mapping between the physical representation of the local algebra and a sub-algebra of the light-front Fock algebra. Conclusion: There is a unitary mapping from the physical representation of the algebra of local observables to a sub-algebra of the light-front Fock algebra with the free light-front Fock vacuum. The dynamics appears in the mapping and the structure of the sub-algebra. This correspondence provides a formulation of locality and Poincaré invariance on the light-front Fock space.
Comments:
17 Pages
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1502.01230 [pdf]
PRD(2015)·12 citations
09
[Submitted on 4 Feb 2015] (cross-list from hep-ph)
Unexpected Mesons X, Y, Z, ... (tetraquarks? hadron molecules? ...)
Ya.I. Azimov🇷🇺
This talk briefly discusses the set of meson resonances discovered in the latest decade. They are frequently treated in the literature as tetraquarks or hadron molecules. Our consideration (using the energy-time uncertainty relation) suggests, however, that the most reasonable description for each of them may be a two- (or more-) component Fock column, with one line being a conventional quark-antiquark pair, and the other line(s) corresponding to a charmed (or beauty) meson-antimeson pair near its threshold. Detailed investigation of decay properties might allow to reveal presence of several Fock components and separate their contributions.
Comments:
5 pages, based on the invited talk at HSQCD-2014; to appear in Nucl. Phys. B Proceedings Suppl.; v2: more accurate formulation in Conclusions; v3: corrected style files
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1502.01279 [pdf]
2 citations
10
[Submitted on 4 Feb 2015] (cross-list from hep-ph)
Azimuthal anisotropies in p+Pb collisions from classical Yang-Mills dynamics
Björn Schenke🇺🇸 · Sören Schlichting🇺🇸 · Raju Venugopalan🇺🇸
We compute single and double inclusive gluon distributions in classical Yang-Mills simulations of proton-lead collisions and extract the associated transverse momentum dependent Fourier harmonics $v_{2} (p_{T})$ and $v_{3} (p_{T})$ . Gluons have a large $v_{2}$ in the initial state, while odd harmonics such as $v_{3}$ vanish identically at the initial time $τ = 0^{+}$ . By the time $τ ≲ 0.4 fm/c$ final state effects in the classical Yang-Mills evolution generate a non-zero $v_{3}$ and only mildly modify the gluon $v_{2}$ . Unlike hydrodynamic flow, these momentum space anisotropies are uncorrelated with the global spatial anisotropy of the collision. A principal ingredient for the generation of $v_{2}$ and $v_{3}$ in this framework is the event-by-event breaking of rotational invariance in domains the size of the inverse of the saturation scale $Q_{s}$ . In contrast to our findings in p+Pb collisions Yang-Mills simulations of lead-lead collisions generate much smaller values of $v_{2, 3} (p_{T})$ and additional collective flow effects are needed to explain experimental data. This is because the locally generated anisotropy due to the breaking of rotational invariance is depleted with the increase in the number of uncorrelated domains.
Comments:
Minor modifications; Version to appear in Phys. Lett. B
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1502.01331 [pdf]
PLB(2015)·145 citations

Affiliations

first authorsco-authorsvia INSPIRE