Nuclear Theory·nucl-th

Monday·November 27, 2017

13 papers—9 primary·4 cross-listed

01
Hydrodynamic predictions for 5.44 TeV Xe+Xe collisions
Giuliano Giacalone🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷
We argue that relativistic hydrodynamics is able to make robust predictions for soft particle production in Xe+Xe collisions at the CERN Large Hadron Collider (LHC). The change of system size from Pb+Pb to Xe+Xe provides a unique opportunity to test the scaling laws inherent to fluid dynamics. Using event-by-event hydrodynamic simulations, we make quantitative predictions for several observables: mean transverse momentum, anisotropic flow coefficients, and their fluctuations. Results are shown as function of collision centrality.
nucl-thhep-phnucl-exPRC(2018)·139 citations
02
Proxy-SU(3): A symmetry for heavy nuclei
D. Bonatsos · I.E. Assimakis · N. Minkov · A. Martinou · S. K. Peroulis · S. Sarantopoulou · R.B. Cakirli · R.F. Casten · K. Blaum
The SU(3) symmetry realized by J. P. Elliott in the sd nuclear shell is destroyed in heavier shells by the strong spin-orbit interaction. On the other hand, the SU(3) symmetry has been used for the description of heavy nuclei in terms of bosons in the framework of the Interacting Boson Approximation, as well as in terms of fermions using the pseudo-SU(3) approximation. A new fermionic approximation, called the proxy-SU(3), has been recently introduced and applied to the even rare earths. We show that the applicability of proxy-SU(3) can be extended to even nuclei in the 28-50 proton shell, to even superheavy elements, as well as to odd-odd and odd rare earths. Parameter free predictions for the beta and gamma deformation parameters are presented and compared to alternative theoretical predictions and to existing data.
nucl-thBulg.J.Phys.(2017)·10 citations
03
Polarization in relativistic heavy ion collisions: a theoretical perspective
F. Becattini🇮🇹
We review the theoretical framework for the calculation of particle polarization in relativistic heavy ion collisions within the hydrodynamical model. The covariant decomposition of the mean spin vector is presented and open theoretical issues addressed.
nucl-thEPJ Web Conf.(2018)·7 citations
04
Semilocal momentum-space regularized chiral two-nucleon potentials up to fifth order
P. Reinert🇩🇪 · H. Krebs🇩🇪 · E. Epelbaum🇩🇪
We introduce new semilocal two-nucleon potentials up to fifth order in the chiral expansion. We employ a simple regularization approach for the pion-exchange contributions which (i) maintains the long-range part of the interaction, (ii) is implemented in momentum space and (iii) can be straightforwardly applied to regularize many-body forces and current operators. We discuss in detail the two-nucleon contact interactions at fourth order and demonstrate that three terms out of fifteen used in previous calculations can be eliminated via suitably chosen unitary transformations. The removal of the redundant contact terms results in a drastic simplification of the fits to scattering data and leads to interactions which are much softer (i.e. more perturbative) than our recent semilocal coordinate-space regularized potentials. Using the pion-nucleon low-energy constants from matching pion-nucleon Roy-Steiner equations to chiral perturbation theory, we perform a comprehensive analysis of nucleon-nucleon scattering and the deuteron properties up to fifth chiral order and study the impact of the leading F-wave two-nucleon contact interactions which appear at sixth order. The resulting chiral potentials lead to an outstanding description of the proton-proton and neutron-proton scattering data from the self-consistent Granada-2013 database below the pion production threshold, which is significantly better than for any other chiral potential. For the first time, the chiral potentials match in precision and even outperform the available high-precision phenomenological potentials, while the number of adjustable parameters is, at the same time, reduced by about ~40%. Last but not least, we perform a detailed error analysis and, in particular, quantify for the first time the statistical uncertainties of the fourth- and the considered sixth-order contact interactions.
nucl-thhep-phnucl-exEPJA(2018)·369 citations
05
Foundations of the proxy-SU(3) symmetry in heavy nuclei
I.E. Assimakis · D. Bonatsos · N. Minkov · A. Martinou · R.B. Cakirli · R.F. Casten · K. Blaum
We show that within the proxy-SU(3) scheme the wave functions of the normal parity orbitals in a given nuclear shell are affected very little as a result of the replacement of the abnormal parity orbitals by their 0[110] proxy-SU(3) counterparts.
nucl-thBulg.J.Phys.(2017)·2 citations
06
Exploring manifestation and nature of a dineutron in two-neutron emission using a dynamical dineutron model
L.V. Grigorenko · J.S. Vaagen · M.V. Zhukov
Emission of two neutrons or two protons in reactions and decays is often discussed in terms of "dineutron" or "diproton" emission. The discussion often leans intuitively on something described by Migdal-Watson approximation. In this work we propose a way to formalize situations of dineutron emission. It is demonstrated that properly formally defined dineutron emission may reveal properties which are drastically different from those traditionally expected, and properties which are actually observed in three-body decays.
nucl-thPRC(2018)·17 citations
07
Individual low-energy toroidal dipole state in $^{24}$ Mg
V.O. Nesterenko · A. Repko · J. Kvasil · P.-G. Reinhard
The low-energy dipole excitations in $^{24}$ Mg are investigated within the Skyrme quasiparticle random-phase-approximation (QRPA) for axial nuclei. The calculations with the force SLy6 reveal a remarkable feature: the lowest $I^{π} K = 1^{-} 1$ excitation (E = 7.92 MeV) in $^{24}$ Mg is a vortical toroidal state (TS) representing a specific vortex-antivortex realization of well-known spherical Hill's vortex in a strongly deformed axial confinement. This is a striking example of an {\it individual} TS which can be much easier discriminated in experiment than the toroidal dipole resonance embracing many states. The TS acquires the lowest energy due to the huge prolate axial deformation in $^{24}$ Mg. The result persists for different Skyrme parameterizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of the TS and its relation with the cluster structure of $^{24}$ Mg. Similar TS could exist in other highly prolate light nuclei. They could serve as promising tests for various reactions to probe a vortical (toroidal) nuclear flow.
nucl-thPRL(2018)·30 citations
08
Phase Transitions in Dense and Hot Matter
Veronica Dexheimer🇺🇸
In this conference proceeding, I discuss in detail the deconfinement to quark matter that takes place at large densities and/or temperatures. The first-order phase transition that is assumed to appear beyond a critical point gives rise to mixtures of phases when more than one globally conserved quantity (such as charge fraction) is imposed. The modifications caused by these mixtures of phases in the QCD phase diagram can have consequences on signals of the existence of quark matter expected to be created in heavy-ion collisions, as well as supernova explosions and neutron-star mergers.
nucl-thastro-ph.HEPoS(2018)·0 citations
09
Drag Induced Radiation and Multi-Stage Effects in Heavy-Flavor Energy Loss
Shanshan Cao🇺🇸 · Abhijit Majumder🇺🇸 · Guang-You Qin🇨🇳 · Chun Shen🇺🇸
It is argued that heavy-quarks traversing a Quark Gluon Plasma, undergo a multi-stage modification process, similar to the case of light flavors. Such an approach is applied to heavy-quark energy loss, which includes a rare-scattering, multiple emission formalism at momenta large compared to the mass (sensitive only to the transverse diffusion coefficient $q^$ ), and a single scattering induced emission formalism (Gunion-Bertsch) at momenta comparable to the mass of the quark [sensitive to $q^$ , and the longitudinal drag ( $e^$ ) and diffusion ( $e^_{2}$ ) coefficients]. The application of such a multi-stage approach within a 2+1D viscous fluid-dynamical simulation leads to simultaneous agreement with experimental data for the nuclear modification factor of both $B$ and $D$ mesons, as measured by the CMS collaboration at the LHC. The extracted transport coefficients are found to be consistent with those for light flavors.
nucl-thhep-phnucl-exPLB(2019)·22 citations
10
Dynamical onset of superconductivity and retention of magnetic fields in cooling neutron stars
Wynn C.G. Ho🇬🇧 · Nils Andersson🇬🇧 · Vanessa Graber🇨🇦
A superconductor of paired protons is thought to form in the core of neutron stars soon after their birth. Minimum energy conditions suggest magnetic flux is expelled from the superconducting region due to the Meissner effect, such that the neutron star core is largely devoid of magnetic fields for some nuclear equation of state and proton pairing models. We show via neutron star cooling simulations that the superconducting region expands faster than flux is expected to be expelled because cooling timescales are much shorter than timescales of magnetic field diffusion. Thus magnetic fields remain in the bulk of the neutron star core for at least 10^6-10^7 yr. We estimate the size of flux free regions at 10^7 yr to be <~ 100 m for a magnetic field of 10^11 G and possibly smaller for stronger field strengths. For proton pairing models that are narrow, magnetic flux may be completely expelled from a thin shell of approximately the above size after 10^5 yr. This shell may insulate lower conductivity outer layers, where magnetic fields can diffuse and decay faster, from fields maintained in the highly conducting deep core.
↳ astro-ph.HEcond-mat.supr-conhep-phnucl-thPRC(2017)·18 citations
11
Collectivity in small systems - Initial state vs. final state effects
Moritz Greif🇩🇪 · Carsten Greiner🇩🇪 · Björn Schenke🇺🇸 · Sören Schlichting🇺🇸 · Zhe Xu🇨🇳
Observations of long rang azimuthal correlations in small collision systems (p+p/A) have triggered an enormous excitement in the heavy-ion community. However, it is presently unclear to what extent the experimentally observed correlations should be attributed to initial state momentum correlations and/or the final state response to the initial state geometry. We discuss how a consistent theoretical description of the non-equilibrium dynamics is important to address both effects within a unified framework and present first results from weakly coupled non-equilibrium simulations in \cite{Greif:2017bnr} to quantify the relative importance of initial state and final state effects based on theoretical calculations.
↳ hep-phnucl-thEPJ Web Conf.(2018)·1 citation
12
Diffusion of conserved charges in relativistic heavy ion collisions
Moritz Greif🇩🇪 · Jan A. Fotakis🇩🇪 · Gabriel S. Denicol🇧🇷 · Carsten Greiner🇩🇪
In order to characterize nuclear matter under extreme conditions, we calculate all diffusion transport coefficients related to baryon, electric and strangeness charge for both a hadron resonance gas and a simplified kinetic model of the quark-gluon plasma. We demonstrate that the diffusion currents do not depend only on gradients of their corresponding charge density. Instead, we show that there exists coupling between the different charge currents, in such a way that it is possible for density gradients of a given charge to generate dissipative currents of another charge. Within this scheme, the charge diffusion coefficient is best viewed as a matrix, in which the diagonal terms correspond to the usual charge diffusion coefficients, while the off-diagonal terms describe the coupling between the different currents. In this letter, we calculate for the first time the complete diffusion matrix including the three charges listed above. We find that the baryon diffusion current is strongly affected by baryon charge gradients, but also by its coupling to gradients in strangeness. The electric charge diffusion current is found to be strongly affected by electric and strangeness gradients, whereas strangeness currents depend mostly on strange and baryon gradients.
↳ hep-phnucl-thPRL(2018)·91 citations
13
Light scalar mesons and two-kaon correlation functions
N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺
It is shown that the recent data on the $K_{S}^{0} K^{+}$ correlation in Pb-Pb interactions agree with the data on the $γ γ \to η π^{0}$ and $ϕ \to η π^{0} γ$ reactions and support the four-quark model of the $a_{0} (980)$ meson. It is shown that the data does not contradict the validity of the Gaussian assumption. The study of two-kaon correlations could provide more information about light scalar mesons after increasing the accuracy of the experimental and theoretical descriptions.
↳ hep-phhep-exnucl-thPRD(2018)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE