Nuclear Theory·nucl-th
21 papers—13 primary·8 cross-listed
[Submitted on 8 Dec 2017]
P. Becker🇫🇷 · D. Davesne🇫🇷 · J. Meyer🇫🇷 · J. Navarro🇪🇸 · A. Pastore🇬🇧
We present recent developments obtained in the so-called N2LO extension of the usual Skyrme pseudo-potential. In particular, we discuss the isovector splitting mass in infinite nuclear matter and the pairing gaps of selected semi-magic even-even nuclei.
[Submitted on 8 Dec 2017]
Mubarak Alqahtani🇺🇸 · Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸
In this paper we review recent progress in relativistic anisotropic hydrodynamics. We begin with a pedagogical introduction to the topic which takes into account the advances in our understanding of this topic since its inception. We consider both conformal and non-conformal systems and demonstrate how one can implement a realistic equation of state using a quasiparticle approach. We then consider the inclusion of non-spheroidal (non-ellipsoidal) corrections to leading-order anisotropic hydrodynamics and present the findings of the resulting second-order viscous anisotropic hydrodynamics framework. We compare the results obtained in both the conformal and non-conformal cases with exact solutions to the Boltzmann equation and demonstrate that, in all known cases, anisotropic hydrodynamics best reproduces the exact solutions. Based on this success, we then discuss the phenomenological application of anisotropic hydrodynamics. Along these lines, we review techniques which can be used to convert a momentum-space anisotropic fluid into hadronic degrees of freedom by generalizing the original idea of Cooper-Frye freeze-out to momentum-space anisotropic systems. And, finally, we present phenomenological results of 3+1d quasiparticle anisotropic hydrodynamic simulations and compare them to experimental data produced in 2.76 TeV Pb-Pb collisions at the LHC. Our results indicate that anisotropic hydrodynamics provides a promising framework for describing the dynamics of the momentum-space anisotropic QGP created in heavy-ion collisions.
[Submitted on 8 Dec 2017]
Zhen Zhang🇺🇸 · Che Ming Ko🇺🇸
Based on the relativistic Vlasov-Uehling-Uhlenbeck transport model, which includes relativistic scalar and vector potentials on baryons, we consider a system in a box with periodic boundary conditions to study the effects of energy conservation in particle production and absorption processes on the equilibrium properties of the system. The density and temperature of the matter in the box are taken to be similar to the hot dense matter formed in heavy ion collisions at intermediate energies. We find that to maintain the equilibrium numbers of , and , which depend on the mean-field potentials of and , requires the inclusion of these potentials in the energy conservation condition that determines the momenta of outgoing particles after a scattering or decay process. We further find that the baryon scalar potentials mainly affect the and pion equilibrium numbers, while the baryon vector potentials have considerable effects on the effective charged pion ratio at equilibrium. Our results thus indicate that it is essential to include in the transport model the effect of potentials in the energy conservation of a scattering or decay process, which is ignored in most transport models, for studying pion production in heavy ion collisions.
[Submitted on 9 Dec 2017]
Heng-Tong Ding🇨🇳 · Olaf Kaczmarek🇨🇳 · Swagato Mukherjee🇺🇸 · Hiroshi Ohno🇺🇸 · Hai-Tao Shu🇨🇳
We present a detailed study of the applications of two stochastic approaches, stochastic optimization method (SOM) and stochastic analytical inference (SAI), to extract spectral functions from Euclidean correlation functions. SOM has the advantage that it does not require prior information. On the other hand, SAI is a more generalized method based on Bayesian inference. Under mean field approximation SAI reduces to the often-used maximum entropy method (MEM), and for a specific choice of the prior SAI becomes equivalent to SOM. To test the applicability of these two stochastic methods to lattice QCD, firstly, we apply these methods to various reasonably chosen model correlation functions, and present detailed comparisons of the reconstructed spectral functions obtained from SOM, SAI and MEM. Next, we present similar studies for charmonia correlation functions obtained from lattice QCD computations using clover-improved Wilson fermions on large, fine, isotropic lattices at and , being the deconfinement transition temperature of a pure gluon plasma. We find that SAI and SOM give consistent results to MEM at these two temperatures.
[Submitted on 9 Dec 2017]
Kamales Kar · Sukhendusekhar Sarkar
The one- plus two-body isospin nonconserving nuclear interactions are included in the prediction of ground state energies of fp shell nuclei using spectral distribution theory. This in turn is used to calculate the linear term in the isobaric mass-multiplet equation and the predictions are then compared to experimental values after the addition of the Coulomb contribution. The agreement is found to be reasonable as observed for sd shell nuclei earlier. One also sees that in this method the contribution to the linear term comes almost completely from the one body isovector Hamiltonian and that results in a huge simplification of the problem.
[Submitted on 10 Dec 2017]
Berndt Müller🇺🇸 · Andreas Schäfer🇩🇪
The yields for hadrons and even light nuclei measured at midrapidity in relativistic heavy ion collisions are found to be dictated exclusively by their thermal Boltzmann factor for a common temperature of approximately 155 MeV. The reason for the validity of the thermal model description is widely discussed. Here, we offer a new type of argument in its favor.
[Submitted on 11 Dec 2017]
P. Buganu🇷🇴 · M. Chabab🇲🇦 · A. El Batoul🇲🇦 · A. Lahbas🇲🇦 · M. Oulne🇲🇦
Motivation : Several theoretical comparisons with experimental data have recently pointed out that the mass tensor of the collective Bohr Hamiltonian cannot be considered as a constant and should be taken as a function of the collective coordinates. Method : The Davydov-Chaban Hamiltonian, describing the collective motion of {\gamma}-rigid atomic nuclei, is modified by allowing the mass to depend on the nuclear deformation. Moreover, the eigenvalue problem for this Hamiltonian is solved for Davidson potential and {\gamma} = 30{\deg} involving an Asymptotic Iteration Method (AIM). The present model is conventionally called Z(4)-DDM-D (Deformation Dependent Mass with Davidson potential), in respect to the so called Z(4) model. Results : Exact analytical expressions are derived for energy spectra and normalized wave functions, for the present model. The obtained results show an overall agreement with the experimental data for 108-116Pd, 128-132Xe, 136;138Ce and 190-198Pt and an important improvement in respect to other models. Prediction of a new candidate nucleus for triaxial symmetry is made. Conclusion : The dependence of the mass on the deformation reduces the increase rate of the moment of inertia with deformation, removing a main drawback of the model and leading to an improved agreement with the corresponding experimental data.
[Submitted on 11 Dec 2017]
W. Ryssens · M. Bender and. P.-H. Heenen
We report on cranked Skyrme-HFB calculations of rotational bands of the octupole-deformed nucleus Th. A sudden change in configuration is observed, with the shape of the yrast state jumping from large octupole deformation at low spin to small octupole deformation at high spin.
[Submitted on 11 Dec 2017]
Boris Tomasik🇸🇰 · Zuzana Paulinyova🇸🇰 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪
Production of deuterons by coalescence has an important influence on the moments of the observed proton number distribution. Therefore, this effect must be taken into account when physics conclusions about baryon number fluctuation are drawn from the measurement of proton number fluctuations. We also show that a measurement of the third and fourth moments of the deuteron number distribution would allow to distinguish whether deuterons are produced statistically or by coalescence.
[Submitted on 7 Dec 2017]
T. Furumoto · T. Suhara · N. Itagaki
Herein, we investigated the channel coupling (CC) effect on the elastic scatterings of lithium (Li) isotopes ( 6--9) for the C and Si targets at 50--60 MeV. The wave functions of the Li isotopes were obtained using the stochastic multi-configuration mixing (SMCM) method based on the microscopic-cluster model. The proton radii of the Li, Li, and Li nuclei became smaller as the number of valence neutrons increased. The valence neutrons in the Li and Li nuclei exhibited a glue-like behavior, thereby attracting the and clusters. Based on the transition densities derived from these microscopic wave functions, the elastic-scattering cross section was calculated using a microscopic coupled-channel (MCC) method with a complex -matrix interaction. The existing experimental data for the elastic scatterings of the Li isotopes and Be nuclei were well reproduced. The Li isotope elastic cross sections were demonstrated for the C and Si targets at =53 MeV. The glue-like effect of the valence neutrons on the Li isotope was clearly demonstrated by the CC effect on elastic scattering. Finally, we realize that the valence neutrons stabilized the bindings of the core parts and the CC effect related to core excitation was indeed reduced.
[Submitted on 11 Dec 2017]
Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇦
By solving a simple kinetic equation, in the relaxation time approximation, and for a particular set of moments of the distribution function, we establish a set of equations which, on the one hand, capture exactly the dynamics of the kinetic equation, and, on the other hand, coincide with the hierarchy of equations of viscous hydrodynamics, to arbitrary order in the viscous corrections. This correspondence sheds light on the underlying mechanism responsible for the apparent success of hydrodynamics in regimes that are far from local equilibrium.
[Submitted on 11 Dec 2017]
Fernando G. Gardim🇧🇷 · Frederique Grassi🇧🇷 · Pedro Ishida🇧🇷 · Matthew Luzum🇧🇷 · Pablo S. Magalhães🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸
An open question in the field of heavy-ion collisions is to what extent the size of initial inhomogeneities in the system affects measured observables. Here we present a method to smooth out these inhomogeneities with minimal effect on global properties, in order to quantify the effect of short-range features of the initial state. We show a comparison of hydrodynamic predictions with original and smoothened initial conditions for four models of initial conditions and various observables. Integrated observables (integrated , scaled distributions, normalized symmetric cumulants, event-plane correlations) as well as most differential observables () show little dependence on the inhomogeneity sizes, and instead are sensitive only to the largest-scale geometric structure. However other differential observables such as the flow factorization ratio and sub-leading principal components are more sensitive to the granularity and could be a good tool to probe the short-scale dynamics of the initial stages of a heavy-ion collision, which are not currently well understood.
[Submitted on 11 Dec 2017]
Roelof Bijker🇲🇽 · Gustavo Guerrero-Navarro🇲🇽 · Emmanuel Ortiz-Pacheco🇲🇽
We discuss some applications of the unquenched quark model which is an extension of the CQM that includes the effects of sea quarks via a 3P0 quark-antiquark pair-creation mechanism. Particular attention is paid to the electromagnetic couplings and beta decays of baryons. It is shown that the observed discrepancies between the experimental data and the predictions of the CQM can be accounted for in large part by the effects of sea quarks in the unquenched quark model.
[Submitted on 28 Aug 2017] (cross-list from hep-ph)
Yang Li🇺🇸 · Kirill Tuchin🇺🇸
We study the electrodynamics of a chiral medium with electric and magnetic charges using the effective Maxwell-Chern-Simons theory extended to include the magnetic current. The exchange of helicity between the chiral medium and the magnetic field, known as the inverse cascade, is controlled by the chiral anomaly equation. In the presence of the magnetic current, the magnetic helicity is dissipated, so that the inverse cascade stops when the magnetic helicity vanishes while the chiral conductivity reaches a non-vanishing stationary value satisfying , where , and are the electric, magnetic and chiral conductivities respectively. We argue that this state is superconducting and exhibits the Meissner effect for both electric and magnetic fields. Moreover, this state is stable with respect to small magnetic helicity fluctuations; the magnetic helicity becomes unstable only when the inequality mentioned above is violated.
[Submitted on 24 Nov 2017] (cross-list from astro-ph.SR)
N. Nishimura · T. Rauscher · R. Hirschi · A. St. J. Murphy · G. Cescutti · C. Travaglio
Thermonuclear supernovae originating from the explosion of a white dwarf accreting mass from a companion star have been suggested as a site for the production of nuclides. Such nuclei are produced during the explosion, in layers enriched with seed nuclei coming from prior strong processing. These seeds are transformed to proton-richer isotopes mainly by photodisintegration reactions. Several thousand trajectories from a 2D explosion model were used in a Monte Carlo approach. Temperature-dependent uncertainties were assigned individually to thousands of rates varied simultaneously in post-processing in an extended nuclear reaction network. The uncertainties in the final nuclear abundances originating from uncertainties in the astrophysical reaction rates were determined. In addition to the 35 classical nuclides, abundance uncertainties were also determined for the radioactive nuclides Nb, Tc, Sm, and for the abundance ratios (Mo)/(Mo), (Nb)/(Mo), (Tc)/(Ru), (Tc)/(Ru), and (Sm)/(Sm), important for Galactic Chemical Evolution studies. Uncertainties found were generally lower than a factor of two, although most nucleosynthesis flows mainly involve predicted rates with larger uncertainties. The main contribution to the total uncertainties comes from a group of trajectories with high peak density originating from the interior of the exploding white dwarf. The distinction between low-density and high-density trajectories allows more general conclusions to be drawn, also applicable to other simulations of white dwarf explosions.
[Submitted on 8 Dec 2017] (cross-list from hep-ph)
Abdel Nasser Tawfik🇪🇬 · Abdel Magied Diab (Egyptian Ctr. Theor. Phys., Cairo and WLCAPP, Cairo)🇪🇬 · T. M. Hussein (Cairo U.)🇪🇬
The linear-sigma model, in which information about confining gluons is included through the Polyakov-loop potential (PLSM), is considered in order to perform a systematic study for various magnetic properties of QCD matter under extreme conditions of high temperatures and densities and finite magnetic field strengths. The introduction of magnetic field to the PLSM Lagrangian requires suitable utilization of Landau quantization, modification in the dispersion relations, and momentum-space dimension-reduction. We observed that increasing the magnetic field leads to filling-up lower Landau levels first and decreasing the number of occupied levels. We conclude that the population of Landau levels is most sensitive to the magnetic field and to the quark charges. The influences of finite magnetic field on the temperature dependence of chiral and deconfinement order-parameter(s) are studied. We present estimations for the magnetization, the magnetic susceptibility, the permeability and the catalysis properties of QCD matter as functions of temperature. The dependences of the resulting freezeout parameters, temperatures and baryon chemical potentials on the corresponding magnetic field strengths have been analyzed, as well. These calculations are compared with recent lattice QCD simulations, whenever available. We conclude that the QCD matter seems to have paramagnetic property at temperatures greater than the critical one. There is an evidence for weak diamagnetic property at low temperatures. Last but not least, we observe that the magnetic catalysis is inverse, namely the critical temperatures decrease with increasing the magnetic field.
[Submitted on 9 Dec 2017] (cross-list from hep-ph)
Muhammad Naeem Anwar🇨🇳 · Yu Lu🇩🇪 · Bing-Song Zou🇨🇳
In heavy quarkonia, hadronic transitions serve as an enlightened probe for the structure and help to establish the understanding of light quark coupling with a heavy degree of freedom. Moreover, in recent years, hadronic transitions revealed remarkable discoveries to identify the new conventional heavy quarkonia and extracting useful information about the so called "XYZ" exotic states. In this contribution, we present our predictions for heavy quark spin symmetry (HQSS) breaking hadronic transitions of higher and wave vector charmonia based on our recently proposed model (inspired by Nambu-Jona-Lasinio (NJL) model) to create light meson(s) in heavy quarkonium transitions. We also suggest spectroscopic quantum numbers for several observed charmoniumlike states. Our analysis indicates that the is most likely to be a dominant state.
[Submitted on 10 Dec 2017] (cross-list from hep-ph)
Yang Li🇺🇸 · Pieter Maris🇺🇸 · James Vary🇺🇸
In light-front dynamics, form factors are traditionally computed with the "good current" within the Drell-Yan frame . Due to truncations imposed in practical calculations, the from factor may acquire frame dependence, which is often neglected. In this work, we explore the form factors in more general frames, preserving the boost covariance. We find the frame dependence of the elastic form factors for mesons is small in basis light-front holography and related models with two-body Fock space truncation. We suggest to use the difference between form factor results from Drell-Yan frame and the "longitudinal frame" as a metric for the violation of the Lorentz symmetry due to Fock space truncation.
[Submitted on 11 Dec 2017] (cross-list from hep-ph)
Francesco Becattini · Marcus Bleicher · Jan Steinheimer · Reinhard Stock
Ideally, the Statistical Hadronization Model (SHM) freeze-out curve should reveal the QCD parton-hadron phase transformation line in the (,) plane. We discuss the effects of various final state interaction phenomena, like baryon-antibaryon annihilation, core-corona effects or QCD critical point formation, which shift or deform the SHM freezeout curve. In particular, we present a method to remove the annihilation effects by quantifying them with the microscopic hadron transport model UrQMD. We further discuss the new aspects of hadronization that could be associated with the relatively broad cross-over phase transformation as predicted by lattice-QCD theory at low . That opens up the possibility that various observables of hadronization, e.g. hadron formation or susceptibilities of higher order (related to grand canonical fluctuations of conserved hadronic charges) may freeze out at different characteristic temperatures. This puts into question the concept of a universal \textit{(pseudo-)critical} temperature, as does the very nature of a cross-over phase transformation.
[Submitted on 11 Dec 2017] (cross-list from hep-ph)
Guruprasad Kadam🇮🇳 · Hiranmaya Mishra🇮🇳 · Lata Thakur🇮🇳
We estimate the electrical and thermal conductivities of hot and dense hadronic matter in the relaxation time approximation of the Boltzmann equation. We estimate the thermodynamical quantities of hot and dense hadronic matter within the ambit of the excluded volume hadron resonance gas model. The relaxation time for all the hadrons is estimated assuming the constant cross section with uniform as well as mass dependent hard-core radius. We compare our results with various existing results. Finally we give an estimate of electrical and thermal conductivities in the context of heavy ion collision experiments.
[Submitted on 11 Dec 2017] (cross-list from hep-ph)
Vadim Lensky🇩🇪 · Franziska Hagelstein🇨🇭 · Vladimir Pascalutsa🇩🇪 · Marc Vanderhaeghen🇩🇪
We derive two new sum rules for the unpolarized doubly virtual Compton scattering process on a nucleon, which establish novel low- relations involving the nucleon's generalized polarizabilities and moments of the nucleon's unpolarized structure functions and . These relations facilitate the determination of some structure constants which can only be accessed in off-forward doubly virtual Compton scattering, not experimentally accessible at present. We perform an empirical determination for the proton and compare our results with a next-to-leading-order chiral perturbation theory prediction. We also show how these relations may be useful for a model-independent determination of the low- subtraction function in the Compton amplitude, which enters the two-photon-exchange contribution to the Lamb shift of (muonic) hydrogen. An explicit calculation of the -resonance contribution to the muonic-hydrogen Lamb shift yields eV, confirming the previously conjectured smallness of this effect.
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