Nuclear Theory·nucl-th

Tuesday·July 5, 2016

11 papers—6 primary·5 cross-listed

01
Electromagnetic effects on meson production: a new tool for studying the space-time evolution of heavy ion collisions
Andrzej Rybicki🇵🇱 · Antoni Szczurek🇵🇱 · Mariola Klusek-Gawenda🇵🇱 · Nikolaos Davis · Vitalii Ozvenchuk🇵🇱 · Miroslaw Kielbowicz🇵🇱
We review our studies of spectator-induced electromagnetic (EM) effects on the emission of charged mesons in the final state of ultrarelativistic heavy ion collisions. We argue that these effects offer sensitivity to the distance $d_{E}$ between the charged meson formation zone at freeze-out and the spectator system. As such, they can serve as an independent, new tool to probe the space-time and longitudinal evolution of the system created in the collision. As a phenomenological application for this tool in the context of resonance production and decay, we obtain a first estimate of the time of pion emission from EM effects. This we compare to existing HBT data.
nucl-thnucl-exEPJ Web Conf.(2016)·4 citations
02
Nucleon localization and fragment formation in nuclear fission
C. L. Zhang · B. Schuetrumpf · W. Nazarewicz
An electron localization measure was originally introduced to characterize chemical bond structures in molecules. Recently, a nucleon localization based on Hartree-Fock densities has been introduced to investigate $α$ -cluster structures in light nuclei. Compared to the local nucleonic densities, the nucleon localization function has been shown to be an excellent indicator of shell effects and cluster correlations. Using the spatial nucleon localization measure, we investigate the emergence of fragments in fissioning heavy nuclei. To illustrate basic concepts of nucleon localization, we employ the self-consistent energy density functional method with a quantified energy density functional optimized for fission studies. We study the particle densities and spatial nucleon localization distributions along the fission pathways of $^{264}$ Fm, $^{232}$ Th and $^{240}$ Pu. We demonstrate that the fission fragments are formed fairly early in the evolution, well before scission. We illustrate the usefulness of the localization measure by showing how the hyperdeformed state of $^{232}$ Th can be understood in terms of a quasimolecular state made of $^{132}$ Sn and $^{100}$ Zr fragments. Compared to nucleonic distributions, the nucleon localization function more effectively quantifies nucleonic clustering: its characteristic oscillating pattern, traced back to shell effects, is a clear fingerprint of cluster/fragment configurations. This is of particular interest for studies of fragment formation and fragment identification in fissioning nuclei.
nucl-thPRC(2016)·63 citations
03
Schematic Interactions with Many Degeneracies
Arun Kingan · Michael Quinonez · Larry Zamick
In previous works we examined the spectra for systems of 2 protons and 2 neutrons, in a single j shell calculation, by obtaining matrix elements from experiment. More recently we considered schematic interactions in the same model space. We continue in this vein here. The present work and the former can be regarded as 2 bookends on a bookshelf.
nucl-thIJMPE(2017)·0 citations
04
The nuclear quadrupole moment mesured with Nuclear Quadrupole Resonance NQR : Principle and definition
Mohamed Belfkir
The nuclear quadruple moment is a fundamental character associated to the nuclei, this moment is related to the not purely spherical distribution in the nuclei, indeed its measure allows us to survey the geometric deformation of the nuclei of its spherical shape. The measurement methods of the quadruple moment is to study the electrical energy hyperfine interaction between the quadruple moment and the electric field gradient due to atomics electrons, one of the methods is the nuclear quadruple resonance NQR which is observed at the transitions between energy levels splits by the effect of the quadruple interaction and induced by a radio frequency field.
nucl-th0 citations
05
Infinite matter properties and zero-range limit of nonrelativistic finite-range interactions
D. Davesne🇫🇷 · P. Becker🇫🇷 · A. Pastore🇬🇧 · J. Navarro🇪🇸
We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin-orbit terms from the spin-isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin-orbit of the M3Y interaction is not compatible with local gauge invariance. Finally, we show that the zero-range limit of both families of interactions coincides with the specific form of the zero-range N3LO Skyrme interaction and we emphasize from this analogy the benefits of N3LO.
nucl-thAnnals Phys.(2016)·21 citations
06
Quasidynamical symmetries in the backbending of chromium isotopes
Raul A. Herrera · Calvin W. Johnson
Background: Symmetries are a powerful way to characterize nuclear wave functions. A true dynamical symmetry, where the Hamiltonian is block-diagonal in subspaces defined by the group, is rare. More likely is a quasidynamical symmetry: states with different quantum numbers (i.e. angular momentum) nonetheless sharing similar group-theoretical decompositions. Purpose: We use group-theoretical decomposition to investigate backbending, an abrupt change in the moment of inertia along the yrast line, in $^{48, 49, 50}$ Cr: prior mean-field calculations of these nuclides suggest a change from strongly prolate to more spherical configurations as one crosses the backbending and increases in angular momentum. Methods: We decompose configuration-interaction shell-model wavefunctions using the SU(2) groups $L$ (total orbital angular momentum) and $S$ (total spin), and the groups SU(3) and SU(4). We do not need a special basis but only matrix elements of Casimir operators, applied with a modified Lanczos algorithm. Results: We find quasidynamical symmetries, albeit often of a different character above and below the backbending, for each group. While the strongest evolution was in SU(3), the decompositions did not suggest a decrease in deformation. We point out with a simple example that mean-field and SU(3) configurations may give very different pictures of deformation. Conclusions: Persistent quasidynamical symmetries for several groups allow us to identify the members of a band and to characterize how they evolve with increasing angular momentum, especially before and after backbending.
nucl-thPRC(2017)·9 citations
07
Towards laboratory detection of topological vortices in superfluid phases of QCD
Arpan Das🇮🇳 · Shreyansh S. Dave🇮🇳 · Somnath De🇮🇳 · Ajit M. Srivastava🇮🇳
Topological defects arise in a variety of systems, e.g. vortices in superfluid helium to cosmic strings in the early universe. There is an indirect evidence of neutron superfluid vortices from glitches in pulsars. One also expects that topological defects may arise in various high baryon density phases of quantum chromodynamics (QCD), e.g. superfluid topological vortices in the color flavor locked (CFL) phase. Though vastly different in energy/length scales, there are universal features, e.g. in the formation of all these defects. Utilizing this universality, we investigate the possibility of detecting these topological superfluid vortices in laboratory experiments, namely heavy-ion collisions. Using hydrodynamic simulations, we show that vortices can qualitatively affect the power spectrum of flow fluctuations. This can give unambiguous signal for superfluid transition resulting in vortices, allowing for check of defect formation theories in a relativistic quantum field theory system, and the detection of superfluid phases of QCD. Detection of nucleonic superfluid vortices in low energy heavy-ion collisions will give opportunity for laboratory controlled study of their properties, providing crucial inputs for the physics of pulsars.
↳ hep-phcond-mat.supr-connucl-exnucl-thMod.Phys.Lett.A(2017)·5 citations
08
Event patterns (particle scatter plots) extracted from charged particle spectra in $pp$ and Pb-Pb collisions at 2.76 TeV
Ya-Hui Chen🇨🇳 · Fu-Hu Liu🇨🇳 · Sakina Fakhraddin🇸🇦 · Magda A. Rahim🇸🇦 · Mai-Ying Duan🇨🇳
The transverse momentum ( $p_{T}$ ) and pseudorapidity ( $η$ ) spectra of charged particles produced in proton-proton ( $pp$ ) and lead-lead (Pb-Pb) collisions at the large hadron collider (LHC) are described by a hybrid model. In the model, the $p_{T}$ spectrum is described by a two-component distribution which contains an inverse power-law suggested by the QCD (Quantum Chromodynamic) calculus and an Erlang distribution resulted from a multisource thermal model. The $η$ spectrum is described by a Gaussian rapidity ( $y$ ) distribution resulted from the Landau hydrodynamic model and the two-component $p_{T}$ distribution, where the conversion between $y$ and $η$ is accurately considered. The modelling results are in agreement with the experimental data measured by the ATLAS Collaboration in $pp$ collisions at center-of-mass energy $s = 2.76$ TeV and in Pb-Pb collisions at center-of-mass energy per nucleon pair $s_{N N} = 2.76$ TeV. Based on the parameter values extracted from $p_{T}$ and $η$ or $y$ spectra, the event patterns or particle scatter plots in three-dimensional velocity and momentum spaces are obtained.
↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2017)·5 citations
09
Single inclusive hadron production in pA collisions at NLO
B. Ducloué🇫🇮 · T. Lappi🇫🇮 · Y. Zhu🇫🇮
We study single inclusive forward hadron production in high energy proton-nucleus collisions at next-to-leading order in the Color Glass Condensate framework. Recent studies have shown that the next-to-leading order corrections to this process are large and negative at large transverse momentum, leading to negative cross sections. We propose to overcome this difficulty by introducing an explicit rapidity factorization scale when subtracting the rapidity divergence into the evolution of the target.
↳ hep-phnucl-thPoS(2016)·0 citations
10
Forward $J / ψ$ production in pA collisions: centrality dependence
B. Ducloué🇫🇮 · T. Lappi🇫🇮 · H. Mäntysaari🇺🇸
The nuclear suppression of forward $J / ψ$ production in high energy proton-nucleus collisions can be used as a probe of gluon saturation at small $x$ . In an earlier work we studied this suppression in minimum bias collisions in the Color Glass Condensate formalism, relying on the optical Glauber model to obtain the dipole cross section of the nucleus from the one of the proton fitted to HERA DIS data. Here we study how the impact parameter dependence of this model can be used to compare our results with recent LHC data on the centrality dependence of this suppression.
↳ hep-phnucl-thPoS(2016)·0 citations
11
Excitation functions of parameters extracted from three-source (net-)proton rapidity distributions in Au-Au and Pb-Pb collisions over an energy range from AGS to RHIC
Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Yan Sun🇨🇳 · Zhu Sun🇨🇳 · Roy A. Lacey🇺🇸
Experimental results of the rapidity spectra of protons and net-protons (protons minus antiprotons) emitted in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions, measured by a few collaborations at the alternating gradient synchrotron (AGS), super proton synchrotron (SPS), and relativistic heavy ion collider (RHIC), are described by a three-source distribution. The values of the distribution width $σ_{C}$ and contribution ratio (relative contribution) $k_{C}$ of the central rapidity region, and the distribution width $σ_{F}$ and rapidity shift $Δ y$ of the forward/backward rapidity regions, are then obtained. The excitation function of $σ_{C}$ increases generally with increase of the center-of-mass energy per nucleon pair $s_{N N}$ . The excitation function of $σ_{F}$ shows a saturation at $s_{N N} = 8.8$ GeV. The excitation function of $k_{C}$ shows a minimum at $s_{N N} = 8.8$ GeV and a saturation at $s_{N N} \approx 17$ GeV. The excitation function of $Δ y$ increase monotonously with $ln s_{N N}$ in the considered energy range.
↳ hep-phhep-exnucl-exnucl-thEPJA(2017)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE