Nuclear Theory·nucl-th

Wednesday·November 28, 2018

7 papers—5 primary·2 cross-listed

01
The overdamped chiral magnetic wave
I. A. Shovkovy🇺🇸 · D. O. Rybalka🇺🇸 · E. V. Gorbar🇺🇦
About eight years ago it was predicted theoretically that a charged chiral plasma could support the propagation of the so-called chiral magnetic waves, which are driven by the anomalous chiral magnetic and chiral separation effects. This prompted intensive experimental efforts in search of signatures of such waves in relativistic heavy-ion collisions. In fact, several experiments have already reported a tentative detection of the predicted signal, albeit with a significant background contribution. Here, we critically reanalyze the theoretical foundations for the existence of the chiral magnetic waves. We find that the commonly used background-field approximation is not sufficient for treating the waves in hot chiral plasmas in the long-wavelength limit. Indeed, the back-reaction from dynamically induced electromagnetic fields turns the chiral magnetic wave into a diffusive mode. While the situation is slightly better in the strongly-coupled near-critical regime of quark-gluon plasma created in heavy-ion collisions, the chiral magnetic wave is still strongly overdamped due to the effects of electrical conductivity and charge diffusion.
nucl-thhep-phhep-thPoS(2018)·17 citations
02
Hadron yields and fluctuations at the CERN Super Proton Synchrotron: system size dependence from Pb+Pb to p+p collisions
A. Motornenko🇩🇪 · V.V. Begun🇵🇱 · V. Vovchenko🇩🇪 · M.I. Gorenstein🇺🇦 · H. Stoecker🇩🇪
The kaon to pion ratio $K^{+} / π^{+}$ and the scaled variance $ω^{-}$ for fluctuations of negatively charged particles are studied within the statistical hadron resonance gas (HRG) model and the Ultra relativistic Quantum Molecular Dynamics (UrQMD) transport model. The calculations are done for p+p, Be+Be, Ar+Sc, and Pb+Pb collisions at the CERN Super Proton Synchrotron energy range to reveal the system size dependence of hadron production. For the HRG calculations the canonical ensemble is imposed for all conserved charges. In the UrQMD simulations the centrality selection in nucleus-nucleus collisions is done by calculating the forward energy $E_{F}$ deposited in the Projectile Spectator Detector, and the acceptance maps of the NA61/SHINE detectors are used. A comparison of the HRG and UrQMD results with the data of the NA61/SHINE Collaboration is done. To understand a difference of the event-by-event fluctuations in p+p and heavy ion collisions the centrality selection procedure in the sample of all inelastic p+p events is proposed and analyzed within the UrQMD simulations.
nucl-thhep-exhep-phnucl-exPRC(2019)·21 citations
03
Phenomenological level density model with hybrid parameterization of deformed and spherical state densities
Naota Furutachi · Futoshi Minato · Osamu Iwamoto
A phenomenological level density model that has different level density parameter sets for the state densities of the deformed and the spherical states, and the optimization of the parameters using experimental data of the average s-wave neutron resonance spacing are presented. The transition to the spherical state from the deformed one is described using the parameters derived from a microscopic nuclear structure calculation. The nuclear reaction calculation has been performed by the statistical model using the present level density. Resulting cross sections for various reactions with the spherical, deformed and transitional target nuclei show a fair agreement with the experimental data, which indicates the effectiveness of the present model. The role of the rotational collective enhancement in the calculations of those cross sections is also discussed.
nucl-thJ.Nucl.Sci.Tech.(2019)·2 citations
04
Nuclides as a liquid phase of $S U (2)_{L} \times S U (2)_{R}$ chiral perturbation theory I: emergence of pion-less SU(2) $χ$ PT
Bryan W. Lynn🇺🇸 · Glenn D. Starkman🇺🇸
The Standard Model of particle physics, augmented with neutrino mixing, is at least very nearly the complete theory of interactions of known particles at energies accessible to Nature on Earth. Candidate effective theories of nuclear structure must therefore reflect SM symmetries, especially the chiral global $S U (2)_{L} \times S U (2)_{R}$ symmetry of two-massless-quark QCD. For ground-state nuclei, SU(2) chiral perturbation theory (XPT) enables perturbation in inverse powers of $Λ_{X S B} ≃ 1 G e V$ , with analytic operators renormalized to all loop orders. We show that pion-less "Static Chiral Nucleon Liquids" (SXNL) emerge as a liquid phase of SU(2) XPT of protons, neutrons and 3 Nambu-Goldstone boson pions. Far-IR pions decouple from SXNL, simplifying the derivation of saturated nuclear matter and microscopic liquid drops (ground-state nuclides). We trace to the global symmetries of two-massless-quark QCD the power of pion-less SU(2) XPT to capture experimental ground-state properties of certain nuclides with even parity, spin zero, even proton number Z, and neutron number N. We derive the SXNL effective SU(2) XPT Lagrangian, including all order $Λ_{X S B}, Λ_{X S B}^{0}$ operators. These include: all 4-nucleon operators that survive Fierz rearrangement in the non-relativistic limit, and effective Lorentz-vector iso-vector neutral " $ρ$ -exchange" operators. SXNL motivate nuclear matter as non-topological solitons at zero pressure: the Nuclear Liquid Drop Model and Bethe-Weizsacker Semi-Empirical Mass Formula emerge in an explicit Thomas-Fermi construction provided in the companion paper. For chosen nuclides, nuclear Density Functional and Skyrme models are justified to order $Λ_{χ S B}^{0}$ . We conjecture that inclusion of higher order operators will result in accurate "natural" Skyrme, No-Core-Shell, and neutron star models.
nucl-th0 citations
05
Weak interference between the 1 $^{-}$ states in the vicinity of $α$ -particle threshold of $^{16}$ O
M. Katsuma
The subthreshold 1 $_{1}^{-}$ state at an excitation energy $E_{x} = 7.12$ MeV in $^{16}$ O has been believed to enhance the $S$ -factor of $^{12}$ C( $α$ , $γ$ ) $^{16}$ O. The enhancement seems to originate from strong interference between 1 $_{1}^{-}$ and 1 $_{2}^{-}$ ( $E_{x} \approx 9.6$ MeV) in the vicinity of the $α$ -particle threshold. However, weak interference between them and a resulting small $E$ 1 $S$ -factor are exemplified with $R$ -matrix theory. Including a higher-order correction of the resonance parameters, the present example appears to reproduce the experimental data consistently. It would therefore be possible that the $E$ 1 $S$ -factor is reduced at low energies.
nucl-thastro-ph.SRnucl-exSpringer Proc.Phys.(2019)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE

The overdamped chiral magnetic wave

Hadron yields and fluctuations at the CERN Super Proton Synchrotron: system size dependence from Pb+Pb to p+p collisions

Phenomenological level density model with hybrid parameterization of deformed and spherical state densities

Nuclides as a liquid phase of SU(2)L​×SU(2)R​ chiral perturbation theory I: emergence of pion-less SU(2) χ PT

Weak interference between the 1− states in the vicinity of α-particle threshold of 16O

Affiliations

Nuclides as a liquid phase of $S U (2)_{L} \times S U (2)_{R}$ chiral perturbation theory I: emergence of pion-less SU(2) $χ$ PT

Weak interference between the 1 $^{-}$ states in the vicinity of $α$ -particle threshold of $^{16}$ O