Nuclear Theory·nucl-th

Wednesday·November 2, 2016

10 papers—5 primary·5 cross-listed

01
Understanding emergent collectivity and clustering in nuclei from a symmetry-based no-core shell-model perspective
A. C. Dreyfuss · K. D. Launey · T. Dytrych · J. P. Draayer · R. B. Baker · C. M. Deibel · C. Bahri
We present a detailed discussion of the structure of the low-lying positive-parity energy spectrum of $^{12}$ C from a no-core shell-model perspective. The approach utilizes a fraction of the usual shell-model space and extends its multi-shell reach via the symmetry-based no-core symplectic shell model (NCSpM) with a simple, physically-informed effective interaction. We focus on the ground-state rotational band, the Hoyle state and its $2^{+}$ and $4^{+}$ excitations, as well as the giant monopole $0^{+}$ resonance, which is a vibrational breathing mode of the ground state. This, in turn, allows us to address the open question about the structure of the Hoyle state and its rotational band. In particular, we find that the Hoyle state is best described through deformed prolate collective modes rather than vibrational modes, while we show that the higher-lying giant monopole $0^{+}$ resonance resembles the oblate deformation of the $^{12}$ C ground state. In addition, we identify the giant monopole $0^{+}$ and quadrupole $2^{+}$ resonances of selected light and intermediate-mass nuclei, along with other observables of $^{12}$ C, including matter rms radii, electric quadrupole moments, as well as $E 2$ and $E 0$ transition rates.
nucl-thPRC(2017)·27 citations
02
Coulomb and nuclear effects in breakup and reaction cross sections
Pierre Descouvemont · L. Felipe Canto · Mahir S. Hussein
We use a three-body Continuum Discretized Coupled Channel (CDCC) model to investigate Coulomb and nuclear effects in breakup and reaction cross sections. The breakup of the projectile is simulated by a finite number of square integrable wave functions. First we show that the scattering matrices can be split in a nuclear term, and in a Coulomb term. This decomposition is based on the Lippmann-Schwinger equation, and requires the scattering wave functions. We present two different methods to separate both effects. Then, we apply this separation to breakup and reaction cross sections of 7Li + 208Pb. For breakup, we investigate various aspects, such as the role of the alpha + t continuum, the angular-momentum distribution, and the balance between Coulomb and nuclear effects. We show that there is a large ambiguity in defining the 'Coulomb' and 'nuclear' breakup cross sections, since both techniques, although providing the same total breakup cross sections, strongly differ for the individual components. We suggest a third method which could be efficiently used to address convergence problems at large angular momentum. For reaction cross sections, interference effects are smaller, and the nuclear contribution is dominant above the Coulomb barrier. We also draw attention on different definitions of the reaction cross section which exist in the literature, and which may induce small, but significant, differences in the numerical values.
nucl-thnucl-exPRC(2017)·15 citations
03
Structural and decay properties of $Z = 132, 138$ superheavy nuclei
Asloob A. Rather · M. Ikram · A. A. Usmani · Bharat Kumar · S. K. Patra
In this paper, we analyze the structural properties of $Z = 132$ and $Z = 138$ superheavy nuclei within the ambit of axially deformed relativistic mean-field framework with NL $3^{*}$ parametrization and calculate the total binding energies, radii, quadrupole deformation parameter, separation energies, density distributions. We also investigate the phenomenon of shape coexistence by performing the calculations for prolate, oblate and spherical configurations. For clear presentation of nucleon distributions, the two-dimensional contour representation of individual nucleon density and total matter density has been made. Further, a competition between possible decay modes such as $α$ -decay, $β$ -decay and spontaneous fission of the isotopic chain of superheavy nuclei with $Z = 132$ within the range 312 $\leq$ A $\leq$ 392 and 318 $\leq$ A $\leq$ 398 for $Z = 138$ is systematically analyzed within self-consistent relativistic mean field model. From our analysis, we inferred that the $α$ -decay and spontaneous fission are the principal modes of decay in majority of the isotopes of superheavy nuclei under investigation apart from $β$ decay as dominant mode of decay in $^{318 - 322} 138$ isotopes.
nucl-thEPJA(2016)·5 citations
04
Wounded quarks at the LHC
Wojciech Broniowski🇵🇱 · Piotr Bozek🇵🇱 · Maciej Rybczynski🇵🇱
We review the results of the wounded quark model, with a stress on eccentricity observables in small systems. A new element is a presentation of symmetric cumulants for the elliptic and triangular flow correlations, obtained in the wounded-quark approach.
nucl-thnucl-exActa Phys.Polon.Supp.(2017)·7 citations
05
Neutrino Mass, Electron Capture and the Shake-off Contributions
Amand Faessler🇩🇪 · Loredana Gastaldo🇩🇪 · Fedor Simkovic🇸🇰
Electron capture can determine the electron neutrino mass, while the beta decay of Tritium measures the electron antineutrino mass and the neutrinoless double beta decay observes the Majorana neutrino mass. Electron capture e. g. on 163Ho plus bound electron to 163Dy* plus neutrino can determine the electron neutrino mass from the upper end of the decay spectrum of the excited Dy*, which is given by the Q-Value minus the neutrino mass. The Dy* states decay by X-ray and Auger electron emissions. The total decay energy is measured in a bolometer. These excitations have been studied by Robertson and by Faessler et al.. In addition the daughter atom Dy can also be excited by moving in the capture process one electron into the continuum. The escape of these continuum electrons is automatically included in the experimental bolometer spectrum. Recently a method developed by Intemann and Pollock was used by DeRujula and Lusignoli for a rough estimate of this shake-off process for "s" wave electrons in capture on 163Ho. The purpose of the present work is to give a more reliable description of "s" wave shake-off in electron capture on Holmium. For that one needs very accurate atomic wave functions of Ho in its ground state and excited atomic wave functions of Dy* including a description of the continuum electrons. In the present approach the wave functions of Ho and Dy* are determined selfconsistently with the antisymmetrized relativistic Dirac-Hartree-Fock approach. The relativistic continuum electron wave functions for the ionized Dy* are obtained in the corresponding selfconsistent Dirac-Hartree-Fock-Potential. In this improved approach shake-off can hardly be seen after electron capture in 163Ho and thus can probably not affect the determination of the electron neutrino mass.
nucl-thhep-phPRC(2017)·24 citations
06
Tracing the pressure of the gluon plasma
G. Jackson🇿🇦 · A. Peshier🇿🇦
Being interested in how a strongly coupled system approaches asymptotic freedom, we re-examine existing precision lattice QCD results for thermodynamic properties of the gluon plasma in a large temperature range. We discuss and thoroughly test the applicability of perturbative results, on which grounds we then infer that the pressure and other bulk properties approach the free limit somewhat slower than previously thought. We also revise the value of the first non-perturbative coefficient in the weak-coupling expansion.
↳ hep-phhep-latnucl-thPRD(2017)·1 citation
07
Efimov Physics: a review
Pascal Naidon🇯🇵 · Shimpei Endo🇦🇺
This article reviews theoretical and experimental advances in Efimov physics, an array of quantum few-body and many-body phenomena arising for particles interacting via short-range resonant interactions, that is based on the appearance of a scale-invariant three-body attraction theoretically discovered by Vitaly Efimov in 1970. This three-body effect was originally proposed to explain the binding of nuclei such as the triton and the Hoyle state of carbon-12, and later considered as a simple explanation for the existence of some halo nuclei. It was subsequently evidenced in trapped ultra-cold atomic clouds and in diffracted molecular beams of gaseous helium. These experiments revealed that the previously undetermined three-body parameter introduced in the Efimov theory to stabilise the three-body attraction typically scales with the range of atomic interactions. The few- and many-body consequences of the Efimov attraction have been since investigated theoretically, and are expected to be observed in a broader spectrum of physical systems.
↳ quant-phcond-mat.quant-gasnucl-thphysics.atom-phRept.Prog.Phys.(2017)·348 citations
08
A chiral covariant approach to $ρρ$ scattering
D. Gülmez🇩🇪 · U.-G. Meißner🇩🇪 · J. A. Oller🇪🇸
We analyze vector meson - vector meson scattering in a unitarized chiral theory based on a chiral covariant framework. We show that a pole assigned to the the scalar meson $f_{0} (1370)$ can be dynamically generated from the $ρρ$ interaction, while this is not the case for the tensor meson $f_{2} (1270)$ as found in earlier works. We show that the generation of the tensor state is untenable due to an artefact of the extreme non-relativistic kinematics used before. We further consider the effects arising from the coupling of channels with different orbital angular momenta. We suggest to use the formalism outlined here to obtain more reliable results for the dynamical generation of resonances in the vector-vector interaction.
↳ hep-phhep-latnucl-thEPJC(2017)·64 citations
09
Collectivity in small collision systems : an initial state perspective
Sören Schlichting🇺🇸 · Prithwish Tribedy🇺🇸
Measurements of multi-particle correlations in the collisions of small systems such as $p + p$ , $p / d /^{3} H e + A$ show striking similarity to the observations in heavy ion collisions. A number of observables measured in the high multiplicity events of these systems resemble features that are attributed to collectivity driven by hydrodynamics. However alternative explanations based on initial state dynamics are able to describe many characteristic features of these measurements. In this brief review we highlight some of the recent developments and outstanding issues in this direction.
↳ hep-phnucl-exnucl-thAdv.High Energy Phys.(2016)·96 citations
10
Axial-Current Matrix Elements in Light Nuclei from Lattice QCD
Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸 · Brian C. Tiburzi🇺🇸 · Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Silas R. Beane🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸
I present results from the first lattice QCD calculations of axial-current matrix elements in light nuclei, performed by the NPLQCD collaboration. Precision calculations of these matrix elements, and the subsequent extraction of multi-nucleon axial-current operators, are essential in refining theoretical predictions of the proton-proton fusion cross section, neutrino-nucleus cross sections and $β β$ -decay rates of nuclei. In addition, they are expected to shed light on the phenomenological quenching of $g_{A}$ that is required in nuclear many-body calculations.
↳ hep-lathep-phnucl-thPoS(2016)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE