Search results for "relativistic"
showing 10 items of 308 documents
Status and perspectives of atomic physics research at GSI
2003
A short overview on the results of atomic physics research at the storage ring ESR is given followed by a presentation of the envisioned atomic physics program at the planned new GSI facility. The proposed new GSI facility will provide highest intensities of relativistic beams of both stable and unstable heavy nuclei - up to a Lorentz factor of 24. At those relativistic velocities, the energies of optical transitions, such as for lasers.. are boosted into the X-ray region and the high-charge state ions generate electric and magnetic fields of exceptional strength. Together with high beam intensities a range of important experiments can be anticipated, for example electronic transitions in r…
Unitarized Chiral Perturbation Theory in a finite volume: scalar meson sector
2011
We develop a scheme for the extraction of the properties of the scalar mesons f0(600), f0(980), and a0(980) from lattice QCD data. This scheme is based on a two-channel chiral unitary approach with fully relativistic propagators in a finite volume. In order to discuss the feasibility of finding the mass and width of the scalar resonances, we analyze synthetic lattice data with a fixed error assigned, and show that the framework can be indeed used for an accurate determination of resonance pole positions in the multi-channel scattering.
Inertial modes in stratified rotating neutron stars : An evolutionary description
2005
With (non-barotropic) equations of state valid even when the neutron, proton and electron content of neutron star cores is not in beta equilibrium, we study inertial and composition gravity modes of relativistic rotating neutron stars. We solve the relativistic Euler equations in the time domain with a three dimensional numerical code based on spectral methods, in the slow rotation, relativistic Cowling and anelastic approximations. Principally, after a short description of the gravity modes due to smooth composition gradients, we focus our analysis on the question of how the inertial modes are affected by non-barotropicity of the nuclear matter. In our study, the deviation with respect to …
Implementing the three-particle quantization condition including higher partial waves
2019
We present an implementation of the relativistic three-particle quantization condition including both $s$- and $d$-wave two-particle channels. For this, we develop a systematic expansion about threshold of the three-particle divergence-free K matrix, $\mathcal{K}_{\mathrm{df,3}}$, which is a generalization of the effective range expansion of the two-particle K matrix, $\mathcal{K}_2$. Relativistic invariance plays an important role in this expansion. We find that $d$-wave two-particle channels enter first at quadratic order. We explain how to implement the resulting multichannel quantization condition, and present several examples of its application. We derive the leading dependence of the …
Relativistic Energy Density Functional Description of Shape Transition in Superheavy Nuclei
2012
Relativistic energy density functionals (REDF) provide a complete and accurate, global description of nuclear structure phenomena. A modern semi-empirical functional, adjusted to the nuclear matter equation of state and to empirical masses of deformed nuclei, is applied to studies of shapes of superheavy nuclei. The theoretical framework is tested in a comparison of calculated masses, quadrupole deformations, and potential energy barriers to available data on actinide isotopes. Self-consistent mean-field calculations predict a variety of spherical, axial and triaxial shapes of long-lived superheavy nuclei, and their alpha-decay energies and half-lives are compared to data. A microscopic, RE…
Probing chemical freeze-out criteria in relativistic nuclear collisions with coarse grained transport simulations
2020
We introduce a novel approach based on elastic and inelastic scattering rates to extract the hyper-surface of the chemical freeze-out from a hadronic transport model in the energy range from E$_\mathrm{lab}=1.23$ AGeV to $\sqrt{s_\mathrm{NN}}=62.4$ GeV. For this study, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model combined with a coarse-graining method is employed. The chemical freeze-out distribution is reconstructed from the pions through several decay and re-formation chains involving resonances and taking into account inelastic, pseudo-elastic and string excitation reactions. The extracted average temperature and baryon chemical potential are then compared to statistic…
A first estimate of $\eta/s$ in Au+Au reactions at E$_{\rm lab}=1.23$ $A$GeV
2020
The HADES experiment at GSI has recently provided data on the flow coefficients $v_1,...,v_4$ for protons in Au+Au reactions at $E_{\rm lab} = 1.23$~$A$GeV (or $\sqrt{s_\mathrm{NN}}=2.4$ GeV). This data allows to estimate the shear viscosity over entropy ratio, $\eta/s$ at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of $\eta/s\approx0.65\pm0.15$ (or $(8\pm2)\,(4\pi)^{-1}$) at such low energies.
Light baryons and their electromagnetic interactions in the covariant constituent quark model
2012
We extend the confined covariant constituent quark model that was previously developed by us for mesons to the baryon sector. In our numerical calculation we use the same values for the constituent quark masses and the infrared cutoff as have been previously used in the meson sector. In a first application we describe the static properties of the proton and neutron, and the $\Lambda$-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers. We discuss in some detail the conservation of gauge invariance of the electromagnetic transition matrix elements in the presence of a nonlocal coupling of the baryons to the three constituent quar…
Influence of temperature-dependent shear viscosity on elliptic flow at backward and forward rapidities in ultrarelativistic heavy-ion collisions
2014
We explore the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta/s$ on the azimuthal anisotropies v_2 and v_4 of hadrons at various rapidities. We find that in Au+Au collisions at full RHIC energy, $\sqrt{s_{NN}}=200$ GeV, the flow anisotropies are dominated by hadronic viscosity at all rapidities, whereas in Pb+Pb collisions at the LHC energy, $\sqrt{s_{NN}}=2760$ GeV, the flow coefficients are affected by the viscosity both in the plasma and hadronic phases at midrapidity, but the further away from midrapidity, the more dominant the hadronic viscosity is. We find that the centrality and rapidity dependence of the elliptic and quadrangular flows can help…
Pinning down QCD-matter shear viscosity in ultrarelativistic heavy-ion collisions via EbyE fluctuations using pQCD + saturation + hydrodynamics
2015
We introduce an event-by-event pQCD + saturation + hydro ("EKRT") framework for high-energy heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order (NLO) perturbative QCD (pQCD) using saturation to control soft particle production, and describe the space-time evolution of the QCD matter with viscous hydrodynamics, event by event (EbyE). We compare the computed centrality dependence of hadronic multiplicities, p_T spectra and flow coefficients v_n against LHC and RHIC data. We compare also the computed EbyE probability distributions of relative fluctuations of v_n, as well as correlations of 2 and 3 event-plane angles, with LHC d…