Nuclear Theory·nucl-th

Wednesday·May 10, 2017

9 papers—7 primary·2 cross-listed

01
Calculations of Shear, Bulk viscosities and Electrical conductivity in Polyakov-Quark-Meson model
Pracheta Singha🇮🇳 · Aman Abhishek🇮🇳 · Guru Kadam🇮🇳 · Sabyasachi Ghosh🇮🇳 · Hiranmaya Mishra🇮🇳
We have evaluated the transport coefficients of quark and hadronic matter in the frame work of Polyakov-Quark-Meson model. The thermal widths of quarks and mesons, which inversely control the strength of these transport coefficients, are obtained from the imaginary part of their respective self-energies at finite temperature. Due to the threshold conditions of their self energies, some limited temperature regions of quark and hadronic phase become relevant for our numerical predictions on transport coefficients, which are grossly in agreement with earlier results.
nucl-thhep-phJ.Phys.G(2019)·43 citations
02
Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC
Heikki Mäntysaari🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Prithwish Tribedy🇺🇸
Results for particle production in root-s = 5.02 TeV p+Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean transverse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.
nucl-thhep-phPLB(2017)·175 citations
03
Modeling pion production in heavy-ion collisions at intermediate energies
Gao-Chan Yong🇨🇳
Pion production in nucleus-nucleus collisions at intermediate energies was modeled in the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model. The effects of nucleon-nucleon short-range correlations in initialization and mean-field potential, isospin-dependent in-medium baryon-baryon elastic and inelastic cross sections and pion in-medium effect are all considered in this model. It is found that the ratio and yields of $π^{-}$ and $π^{+}$ in Au+Au reaction at 400 MeV/nucleon reproduce the FOPI/GSI data very well especially with a soft symmetry energy in the present transport model. Predictions on the single and double $π^{-} / π^{+}$ ratio are made for the isotope reaction systems $^{132} Sn +^{124} Sn$ and $^{108} Sn +^{112} Sn$ at 300 MeV/nucleon since related experiments are being carried out at RIKEN/Japan.
nucl-thnucl-exPRC(2017)·38 citations
04
Global analysis of quadrupole shape invariants based on covariant energy density functionals
S. Quan · Q. Chen · Z. P. Li · T. Niksic · D. Vretenar
Coexistence of different geometric shapes at low energies presents a universal structure phenomenon that occurs over the entire chart of nuclides. Studies of the shape coexistence are important for understanding the microscopic origin of collectivity and modifications of shell structure in exotic nuclei far from stability. The aim of this work is to provide a systematic analysis of characteristic signatures of coexisting nuclear shapes in different mass regions, using a global self-consistent theoretical method based on universal energy density functionals and the quadrupole collective model. The low-energy excitation spectrum and quadrupole shape invariants of the two lowest $0^{+}$ states of even-even nuclei are obtained as solutions of a five-dimensional collective Hamiltonian (5DCH) model, with parameters determined by constrained self-consistent mean-field calculations based on the relativistic energy density functional PC-PK1, and a finite-range pairing interaction. The theoretical excitation energies of the states: $2_{1}^{+}$ , $4_{1}^{+}$ , $0_{2}^{+}$ , $2_{2}^{+}$ , $2_{3}^{+}$ , as well as the $B (E 2; 0_{1}^{+} \to 2_{1}^{+})$ values, are in very good agreement with the corresponding experimental values for 621 even-even nuclei. Quadrupole shape invariants have been implemented to investigate shape coexistence, and the distribution of possible shape-coexisting nuclei is consistent with results obtained in recent theoretical studies and available data. The present analysis has shown that, when based on a universal and consistent microscopic framework of nuclear density functionals, shape invariants provide distinct indicators and reliable predictions for the occurrence of low-energy coexisting shapes. This method is particularly useful for studies of shape coexistence in regions far from stability where few data are available.
nucl-thPRC(2017)·35 citations
05
Spin-orbit splittings of neutron states in $N = 20$ isotones from covariant density functionals and their extensions
Konstantinos Karakatsanis · G. A. Lalazissis · Peter Ring · Elena Litvinova
Spin-orbit splitting is an essential ingredient for our understanding of the shell structure in nuclei. One of the most important advantages of relativistic mean-field (RMF) models in nuclear physics is the fact that the large spin-orbit (SO) potential emerges automatically from the inclusion of Lorentz-scalar and -vector potentials in the Dirac equation. It is therefore of great importance to compare the results of such models with experimental data. We investigate the size of $2 p$ and $1 f$ splittings for the isotone chain $^{40}$ Ca, $^{38}$ Ar, $^{36}$ S, and $^{34}$ Si in the framework of various relativistic and nonrelativistic density functionals. They are compared with the results of nonrelativistic models and with recent experimental data.
nucl-thPRC(2017)·19 citations
06
Dynamical dissociation of quarkonia by wave function decoherence
Shiori Kajimoto🇯🇵 · Yukinao Akamatsu🇯🇵 · Masayuki Asakawa🇯🇵 · Alexander Rothkopf🇩🇪
We investigate the real-time evolution of quarkonium bound states in a quark-gluon plasma in one dimension using an improved QCD based stochastic potential model. This model describes the quarkonium dynamics in terms of a Schrödinger equation with an in-medium potential and two noise terms encoding the residual interactions between the heavy quarks and the medium. The probabilities of bound states in a static medium and in a boost-invariantly expanding quark-gluon plasma are discussed. We draw two conclusions from our results: One is that the outcome of the stochastic potential model is qualitatively consistent with the experimental data in relativistic heavy-ion collisions. The other is that the noise plays an important role in order to describe quarkonium dynamics in medium, in particular it causes decoherence of the quarkonium wave function. The effectiveness of decoherence is controlled by a new length scale $l_{corr}$ . It represents the noise correlation length and its effect has not been included in existing phenomenological studies.
nucl-thhep-phnucl-exPRD(2018)·90 citations
07
Faddeev calculations for light $Ξ$ -hypernuclei
Igor Filikhin🇺🇸 · Vladimir M. Suslov🇺🇸 · Branislav Vlahovic🇺🇸
The hypernuclear systems $N N Ξ$ and $ΞΞ N$ are considered as an analogue of $nn p$ ( $^{3}$ H) nuclear system (with the notation as $AA B$ system). We use the recently proposed modification for the $s$ -wave Malfliet-Tjon potential. The modification simulates the Extended-Soft-Core model (ESC08c) for baryon-baryon interactions. The $Ξ N$ spin/isospin triplet $(S, I) = (1, 1)$ potential generates a bound state with the energy $B_{2} (A B)$ =1.56~MeV. Three-body binding energy $B_{3}$ for the states with maximal total isospin is calculated employing the configuration-space Faddeev equations. Comparison with the results obtained within the integral representation for the equations is presented. The different types of the relation between $B_{2}$ and $B_{3} (V_{AA} = 0)$ are discussed.
nucl-thMath.Model.Geom.(2017)·13 citations
08
Bayesian analysis of quark spectral properties from the Dyson-Schwinger equation
Christian S. Fischer🇩🇪 · Jan M. Pawlowski🇩🇪 · Alexander Rothkopf🇩🇪 · Christian A. Welzbacher🇩🇪
We report results on the quark spectral function in the Landau gauge at finite temperature determined from its Dyson-Schwinger equation. Compared to earlier quenched results this study encompasses unquenched $N_{f} = 2 + 1$ fermion flavors in the medium. For the reconstruction of real-time spectra we deploy a recent Bayesian approach (BR method) and develop a new prior in order to better assess the inherent systematic uncertainties. We identify the quark quasi-particle spectrum and analyze the (non-)appearance of zero modes at or around the pseudo-critical temperature. In both, the fully unquenched system and a simpler truncation using a model for the gluon propagator we observe a characteristic three-peak structure at zero three-momentum. The temperature dependence of these structures in case of the gluon propagator model is different than observed in previous studies. For the back-coupled and unquenched case we find interesting modifications at and around the pseudo-critical transition temperature.
↳ hep-phnucl-thPRD(2018)·40 citations
09
Phase structure of NJL model with weak renormalization group
Ken-Ichi Aoki🇯🇵 · Shin-Ichiro Kumamoto🇯🇵 · Masatoshi Yamada🇩🇪
We analyze the chiral phase structure of the Nambu--Jona-Lasinio model at finite temperature and density by using the functional renormalization group (FRG). The renormalization group (RG) equation for the fermionic effective potential $V (σ; t)$ is given as a partial differential equation, where $σ := ψ ˉ ψ$ and $t$ is a dimensionless RG scale. When the dynamical chiral symmetry breaking (D $χ$ SB) occurs at a certain scale $t_{c}$ , $V (σ; t)$ has singularities originated from the phase transitions, and then one cannot follow RG flows after $t_{c}$ . In this study, we introduce the weak solution method to the RG equation in order to follow the RG flows after the D $χ$ SB and to evaluate the dynamical mass and the chiral condensate in low energy scales. It is shown that the weak solution of the RG equation correctly captures vacuum structures and critical phenomena within the pure fermionic system. We show the chiral phase diagram on temperature, chemical potential and the four-Fermi coupling constant.
↳ hep-thcond-mat.stat-mechhep-phnucl-thNPB(2018)·33 citations

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