Nuclear Theory·nucl-th

Wednesday·November 29, 2017

17 papers—11 primary·6 cross-listed

01
$ϕ$ meson in nuclear matter and nuclei
J. J. Cobos-Martínez🇲🇽 · K.Tsushima🇧🇷 · G. Krein🇧🇷 · A. W. Thomas🇦🇺
The mass and decay width of the $ϕ$ meson in cold nuclear matter are computed in an effective Lagrangian approach, with the medium dependence of these properties obtained by evaluating kaon-antikaon loop contributions to the $ϕ$ self-energy. At normal nuclear matter density, we find a downward shift of the $ϕ$ mass by a few percent, while the decay width is enhanced by an order of magnitude. We also present $ϕ$ --nucleus bound state energies and absorption widths for some selected nuclei, using complex optical potentials obtained in the local density approximation. Our results suggest that the $ϕ$ should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.
nucl-thhep-phnucl-exPoS(2018)·3 citations
02
Transport coefficients in a finite volume Polyakov--Nambu--Jona-Lasinio model
Kinkar Saha🇮🇳 · Sabyasachi Ghosh🇮🇳 · Sudipa Upadhaya🇮🇳 · Soumitra Maity🇮🇳
Finite size consideration of matter significantly affects transport coefficients like shear viscosity, bulk viscosity, electrical conductivity, which we have investigated here in the framework of the Polyakov-Nambu-Jona-Lasinio model. Owing to the basic quantum mechanics, a non-zero lower momentum cut-off is implemented in momentum integrations, used in the expressions of constituent quark masses and transport coefficients. When the system size decreases, the values of these trans- port coefficients are enhanced in low temperature range. At high temperature domain, shear viscos- ity and electrical conductivity become independent of system sizes. Whereas, bulk viscosity, which is associated with scale violating quantities of the system, faces some non-trivial size dependence in this regime. In the phenomenological direction, our microscopic estimations can also be linked with the macroscopic outcome, based on dissipative hydrodynamical simulation.
nucl-thhep-phPRD(2018)·33 citations
03
Structures in the nuclear electric-dipole spectrum
P. Papakonstantinou
I undertake an anatomy of the nuclear electric-dipole spectrum and discuss selected observations. First, using data and calculations on 208Pb as a representative case, I identify five conspicuous structures in the spectra of heavy nuclei: (1) the giant dipole resonance (GDR), (2) the dipole compression mode, (3) the isoscalar low-energy dipole mode (IS-LED),(4) the isoscalar mode in the region of the GDR, and (5) a concentration of "pygmy" dipole strength (PDS) between the latter two. Next, compiling the data from Texas A&M I show that the energy of (4) follows roughly a A^{-1/6} dependence on the mass number. Finally, I summarize recent theoretical studies on the PDS in exotic nuclei, which suggest a strong influence of shell effects and loose binding.
nucl-thnucl-exIn Proceedings of the International Sympo…·0 citations
04
Traces of non-equilibrium dynamics in relativistic heavy-ion collisions
Pierre Moreau🇩🇪 · Yingru Xu🇺🇸 · Taesoo Song🇩🇪 · Marlene Nahrgang🇺🇸 · Steffen Bass🇺🇸 · Elena Bratkovskaya🇩🇪
The impact of non-equilibrium effects on the dynamics of heavy-ion collisions is investigated by comparing a non-equilibrium transport approach, the Parton-Hadron-String-Dynamics (PHSD), to a 2D+1 viscous hydrodynamical model, which is based on the assumption of local equilibrium and conservation laws. Starting the hydrodynamical model from the same non-equilibrium initial condition as in the PHSD, using an equivalent lQCD Equation-of-State (EoS), the same transport coefficients, i.e. shear viscosity $η$ and the bulk viscosity $ζ$ in the hydrodynamical model, we compare the time evolution of the system in terms of energy density, Fourier transformed energy density, spatial and momentum eccentricities and ellipticity in order to quantify the traces of non-equilibrium phenomena. In addition, we also investigate the role of initial pre-equilibrium flow on the hydrodynamical evolution and demonstrate its importance for final state observables. We find that due to non-equilibrium effects, the event-by-event transport calculations show large fluctuations in the collective properties, while ensemble averaged observables are close to the hydrodynamical results.
nucl-thPoS(2018)·2 citations
05
Interaction of antiprotons with nuclei
Jaroslava Hrtánková🇨🇿 · Jiří Mareš🇨🇿
We report on self-consistent calculations of $p ˉ$ quasi-bound states in selected nuclei performed within the relativistic mean-field (RMF) model employing $p ˉ$ coupling constants tuned to reproduce $p ˉ$ -atom data. We confirmed considerable polarization of the nuclear core induced by the antiproton. The $p ˉ$ annihilation was treated dynamically, taking into account the reduced phase space in the nuclear medium as well as the compressed nuclear density. The energy available for the annihilation products was evaluated self-consistently, considering additional energy shift due to particle momenta in the $p ˉ$ -nucleus system. Next, we constructed the $p ˉ$ -nucleus optical potential using scattering amplitudes related to the latest version of the Paris $N ˉ N$ potential. We explored energy dependence of the potential and the implications for $p ˉ$ -nucleus quasi-bound states.
nucl-thJPS Conf.Proc.(2017)·0 citations
06
Spin-isospin excitation of $^{3}$ He with three-proton final state
Souichi Ishikawa
Spin-isospin excitation of $^{3}$ He nucleus by proton-induced charge-exchange reaction, $^{3} He (p, n) ppp$ , at forward neutron scattering angle is studied in a plane wave impulse approximation (PWIA). In PWIA, cross sections of the reaction is written in terms of proton-neutron scattering amplitudes and response functions of the transition from $^{3}$ He to three-proton state by spin-isospin transition operators. The response functions are calculated with realistic nucleon-nucleon potential models using a Faddeev three-body method. Calculated cross sections agree with available experimental data in substance. Possible effects arising from the uncertainty of proton-neutron amplitudes and three-nucleon interactions in three-proton system are examined.
nucl-thnucl-exPTEP(2018)·3 citations
07
Dilepton production and resonance properties within a new hadronic transport approach in the context of the GSI-HADES experimental data
Jan Staudenmaier🇩🇪 · Janus Weil🇩🇪 · Vinzent Steinberg🇩🇪 · Stephan Endres🇩🇪 · Hannah Petersen🇩🇪
The dilepton emission in heavy-ion reactions at low beam energies is examined within a hadronic transport approach. In this article the production of electron-positron pairs from a new approach named SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. The dilepton emission is consistently taken into account below the hadronic threshold. The calculations are systematically confronted with HADES data in the kinetic energy range of $1 - 3.5 A$ GeV for elementary, proton-nucleus and nucleus-nucleus reactions. The present approach employing a resonance treatment based on vacuum properties is validated by an excellent agreement with experimental data up to system sizes of carbon-carbon collisions. After establishing this well-understood baseline in elementary and small systems, the significance of medium effects is investigated with a coarse-graining approach based on the same hadronic evolution. The effect of explicit in-medium modifications to the vector meson spectral functions is important for dilepton invariant mass spectra in ArKCl and larger systems, even though the transport approach with vacuum properties reveals similar features due the coupling to baryonic resonance and the intrinsically included collisional broadening. This article provides a comprehensive comparison of our calculations with published dielectron results from the HADES collaboration. In addition, the emission of dileptons is predicted in gold-gold and pion-beam experiments for which results are expected soon.
nucl-thhep-phnucl-exPRC(2018)·62 citations
08
Higher cumulants of baryon number in critical QCD
Nikolaos G. Antoniou🇬🇷 · Fotios K. Diakonos🇬🇷 · Nikolaos Kalntis🇬🇷 · Alexandros Kanargias🇬🇷
We study the higher moments of the baryon number in the immediate neighbourhood of the QCD critical endpoint within the framework of Ising-QCD thermodynamics (N.~G. Antoniou {\it et al}, arXiv:1705.09124 [hep-ph]). We show that the kurtosis, as a function of the freeze-out baryon chemical potential, attains a sharp minimum very close to the critical point. We argue that the sharpness of this minimum is due to the narrowness of the critical region in the chemical potential direction. Our analysis reveals that the broad minimum of the kurtosis observed in Au+Au central collisions at STAR (in RHIC-BES I) in the colliding energy region $17$ GeV $< s <$ $39$ GeV is apparently only a precursor of the critical point and not a signature of its location.
nucl-thhep-phNPA(2019)·4 citations
09
Bound states of the $D$ -dimensional Schrödinger equation for the generalized Woods-Saxon potential
V. H. Badalov · B. Baris · K. Uzun
In this paper, the approximate analitical solutions of the hyper-radial Schrödinger equation are obtained for the generalized Wood-Saxon potential by implementing the Pekeris approximation to surmount the centrifugal term. The energy eigenvalues and corresponding hyper-radial wave functions are found for any angular momentum case via the Nikiforov-Uvarov (NU) and Supersymmetric quantum mechanics (SUSY QM) methods. Hence, the same expressions are obtained for the energy eigenvalues, and the expression of hyper-radial wave functions transformed each other is shown owing to these methods. Furthermore, a finite number energy spectrum depending on the depths of the potential well $V_{0}$ and $W$ , the radial $n_{r}$ and $l$ orbital quantum numbers and parameters $D, a, R_{0}$ are also identified in detail. Finally, the bound state energies and the corresponding normalized hyper-radial wave functions for the neutron system of the a $^{56} F e$ nucleus are calculated in $D = 2$ and $D = 3$ , as well as the energy spectrum expressions of other highest dimensions are identified by using the energy spectrum of $D = 2$ and $D = 3$ .
nucl-thmath-phmath.MPMod.Phys.Lett.A(2019)·8 citations
10
FSQP nuclear matrix elements for two neutrino double beta decays
Hiroyasu Ejiri🇯🇵
Nuclear matrix elements (NMEs) for two neutrino double beta decays are discussed in terms of the Fermi Surface Quasi-Particle (FSQP) Model. The evaluated NMEs agree with the observed NMEs . The new NMEs for two neutrino double beta decays from Kr78, Cd106, Ba130, and Pd110 were evaluated by FSQP. The NMEs show shell configuration dependence. Impacts of the FSQP NMEs for two neutrino double beta decays on the NMEs for neutrino less double beta decays are discussed.
nucl-thnucl-exJ.Phys.G(2017)·17 citations
11
Charmonium spectral functions in $p ˉ A$ collision
Gy. Wolf🇭🇺 · G. Balassa🇭🇺 · P. Kovács🇭🇺 · M. Zétényi🇭🇺 · Su Houng Lee🇰🇷
We study the in-medium propagation of low-lying charmonium states: $J /Ψ$ , $Ψ$ (3686), and $Ψ$ (3770) in a $p ˉ$ Au $10$ GeV collision. This energy regime will be available for the PANDA experiment. The time evolution of the spectral functions of the charmonium states is studied with a BUU type transport model. We observe a substantial effect of the medium in the dilepton spectrum.
nucl-thActa Phys.Polon.Supp.(2017)·5 citations

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