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
12
Vector boson tagged jets and jet substructure
Ivan Vitev🇺🇸
In these proceedings, we report on recent results related to vector boson-tagged jet production in heavy ion collisions and the related modification of jet substructure, such as jet shapes and jet momentum sharing distributions. $Z^{0}$ -tagging and $γ$ -tagging of jets provides new opportunities to study parton shower formation and propagation in the quark-gluon plasma and has been argued to provide tight constrains on the energy loss of reconstructed jets. We present theoretical predictions for isolated photon-tagged and electroweak boson-tagged jet production in Pb+Pb collisions at $s_{N N} = 5.02$ TeV at the LHC, addressing the modification of their transverse momentum and transverse momentum imbalance distributions. Comparison to recent ATLAS and CMS experimental measurements is performed that can shed light on the medium-induced radiative corrections and energy dissipation due to collisional processes of predominantly quark-initiated jets. The modification of parton splitting functions in the QGP further implies that the substructure of jets in heavy ion collisions may differ significantly from the corresponding substructure in proton-proton collisions. Two such observables and the implication of tagging on their evaluation is also discussed.
↳ hep-phnucl-exnucl-thEPJ Web Conf.(2018)·1 citation
13
Comment on `Nucleon Structure Functions from Operator Product Expansion on the Lattice'
Keh-Fei Liu🇺🇸
It is suggested in the paper by A.J. Chambers {\it et al.} (Phys. Rev. Lett. 118, 242001 (2017), arXiv:1703.01153) that the time-ordered current-curent correlator in the nucleon calculated on the lattice is to be identified as the forward Compton amplitude so that it is related to the sum of the even moments of the structure function as in the Minkowski space in the continuum. We point out two problems with this identification. First of all, the current-current correlator defined in the Euclidean space is not analytic everywhere on the rest of the complex $ν$ or $ω$ plane, besides the cuts on the real axis. As such, there is no dispersion relation to relate it to its imaginary part and hence the moments of the structure function. On the lattice, there is an additional difficulty in that the higher dimensional local operators from the operator production expansion (OPE) of the current-current product can mix with lower dimensional higher-twist operators which leads to divergences in the powers of inverse lattice spacing. This mixing needs to be removed before their matrix elements can be identified as the moments of the structure function.
↳ hep-phhep-latnucl-th0 citations
14
3D structure of hadrons by generalized distribution amplitudes and gravitational form factors
S. Kumano🇯🇵 · Qin-Tao Song🇯🇵 · O. V. Teryaev🇷🇺
Generalized distribution amplitudes (GDAs) are one type of three-dimensional structure functions, and they are related to the generalized distribution functions (GPDs) by the $s$ - $t$ crossing of the Mandelstam variables. The GDA studies provide information on three-dimensional tomography of hadrons. The GDAs can be investigated by the two-photon process $γ^{*} γ \to h h ˉ$ , and the GPDs are studied by the deeply virtual Compton scattering $γ^{*} h \to γ h$ . The GDA studies had been pure theoretical topics, although the GPDs have been experimentally investigated, because there was no available experimental measurement. Recently, the Belle collaboration reported their measurements on the $γ^{*} γ \to π^{0} π^{0}$ differential cross section, so that it became possible to find the GDAs from their measurements. Here, we report our analysis of the Belle data for determining the pion GDAs. From the GDAs, the timelike gravitational form factors $Θ_{1} (s)$ and $Θ_{2} (s)$ can be calculated, which are mechanical (pressure, shear force) and mass (energy) form factors, respectively. They are converted to the spacelike form factors by using the dispersion relation, and then gravitational radii are evaluated for the pion. The mass and mechanical radii are obtained from $Θ_{2}$ and $Θ_{1}$ as $⟨ r^{2} ⟩_{mass} = 0.56 \sim 0.69$ fm and $⟨ r^{2} ⟩_{mech} = 1.45 \sim 1.56$ fm, whereas the experimental charge radius is $⟨ r^{2} ⟩_{charge} = 0.672 \pm 0.008$ fm for the charged pion. Future developments are expected in this new field to explore gravitational physics in the quark and gluon level.
↳ hep-phhep-exhep-latnucl-thPoS(2018)·0 citations
15
$Ab initio$ calculation of the calorimetric electron capture spectrum of $^{163}$ Holmium: Intra-atomic decay into bound-states
M. Braß · C. Enss · L. Gastaldo · M.W. Haverkort
The determination of the electron neutrino mass by electron capture in $^{163}$ Ho relies on a precise understanding of the deexcitation of a core hole after an electron capture event. We here present an \textit{ab intio} calculation of the electron capture spectrum in $^{163}$ Ho, including all intra-atomic decay channels into bound-states. We use theoretical methods developed for the calculation of core level spectroscopy on correlated electron compounds. Our comparison critically tests the reality of these theories. We find that relativistic interactions beyond the Dirac equation, i.e. quantum-electro dynamics, only lead to minor shifts of the spectral peaks. The electronic relaxation after an electron capture event due to the changed nuclear potential leads to a mixing of different edges, but due to conservation of angular momentum of each scattered electron, no additional structures emerge. Many-body Coulomb interactions lead to the formation of multiplets and to additional peaks with multiple core-holes due to Auger decay. Multiplets crucially change the appearance of the resonances on a Rydberg energy scale. The additional structures due to Auger decay are, although clearly visible, relatively weak compared to the one core hole states and accidentally far away from the end-point region of the spectrum. As the end-point of the spectrum is effected most by the neutrino mass these additional states do not influence the statistics for determining the neutrino mass directly. The multiplet broadening and Auger shake-up of the main core-level edges do change the apparent line-width and accompanying lifetime of these edges, thereby invalidating experimentally obtained lifetimes at the resonance for regions far away from the resonance.
↳ physics.atom-phcond-mat.str-elnucl-thPRC(2018)·29 citations
16
Hyperasymptotics and quark-hadron duality violations in QCD
Diogo Boito🇧🇷 · Irinel Caprini🇷🇴 · Maarten Golterman🇪🇸 · Kim Maltman🇦🇺 · Santiago Peris🇪🇸
We investigate the origin of the quark-hadron duality-violating terms in the expansion of the QCD two-point vector correlation function at large energies in the complex $q^{2}$ plane. Starting from the dispersive representation for the associated polarization, the analytic continuation of the operator product expansion from the Euclidean to the Minkowski region is performed by means of a generalized Borel-Laplace transform, borrowing techniques from hyperasymptotics. We establish a connection between singularities in the Borel plane and quark-hadron duality violating contributions. Starting with the assumption that for QCD at $N_{c} = \infty$ the spectrum approaches a Regge trajectory at large energy, we obtain an expression for quark-hadron duality violations at large, but finite $N_{c}$ .
↳ hep-phhep-thnucl-thPRD(2018)·57 citations
17
Canonical transformation path to gauge theories of gravity II --- Spacetime coupling of spin-0 and spin-1 particle fields
J. Struckmeier🇩🇪 · J. Muench🇩🇪 · P. Liebrich🇩🇪 · M. Hanauske🇩🇪 · J. Kirsch🇩🇪 · D. Vasak🇩🇪 · L. Satarov🇩🇪 · H. Stoecker🇩🇪
The generic form of spacetime dynamics as a classical gauge field theory has recently been derived, based on only the action principle and on the Principle of General Relativity. It was thus shown that Einstein's General Relativity is the special case where (i) the Hilbert Lagrangian (essentially the Ricci scalar) is supposed to describe the dynamics of the "free" (uncoupled) gravitational field, and (ii) the energy-momentum tensor is that of scalar fields representing real or complex structureless (spin- $0$ ) particles. It followed that all other source fields---such as vector fields representing massive and non-massive spin- $1$ particles---need careful scrutiny of the appropriate source tensor. This is the subject of our actual paper: we discuss in detail the coupling of the gravitational field with (i) a massive complex scalar field, (ii) a massive real vector field, and (iii) a massless vector field. We show that different couplings emerge for massive and non-massive vector fields. The \emph{massive} vector field has the \emph{canonical} energy-momentum tensor as the appropriate source term---which embraces also the energy density furnished by the internal spin. In this case, the vector fields are shown to generate a torsion of spacetime. In contrast, the system of a \emph{massless} and charged vector field is associated with the \emph{metric} (Hilbert) energy-momentum tensor due to its additional $U (1)$ symmetry. Moreover, such vector fields do not generate a torsion of spacetime. The respective sources of gravitation apply for all models of the dynamics of the `free' (uncoupled) gravitational field---which do not follow from the gauge formalism but must be specified based on separate physical reasoning.
↳ gr-qchep-thnucl-thIJMPE(2019)·16 citations

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