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At least 37 records · Page 2Linked to original sources
arXiv2007

Electroweak Hard Photon Bremsstrahlung in Electron-Nucleon Scattering

One way to treat the infrared divergences of the electroweak Next-to-Leading-Order (NLO) differential cross sections to parity-violating (PV) electron-proton scattering is by adding soft-photon emission contribution. Although more physical, the results are left with a logarithmic dependence on the photon detector acceptance, which can only be eliminated by considering Hard Photon Bremsstrahlung (HPB) contribution. Here we present a treatment of HPB for PV electron-proton scattering. HPB differential cross sections for electron-proton scattering have been computed using the experimental values of nucleon form factors. The final results are expressed through kinematic parameters, making it possible to apply the computed PV HPB differential cross sections for the analysis of data of a range of current and proposed experiments.

nucl-th↗
arXiv2009

Effective potentials for heavy quarks above deconfinement

Using methods previously developed by Kelbg and others for creating effective potentials for electron-ion plasmas, we investigate quarkonium potentials above deconfinement. Using results for the internal energy of a static quark-antiquark pair, a set of effective potentials are constructed that take into account quantum effects and symmetry conditions. Bound state effects are explicitly included in order to account for the strongly coupled nature of plasmas. It is hoped that these effective potentials will be useful in simulations of heavy quarks or plasma quasiparticles when the dynamics is treated classically.

nucl-th↗
arXiv2007

The Role of Surface Tension for the Equation of State of Quark-Gluon Bags

The temperature and chemical potential dependent surface tension of bags is introduced into the gas of quark-gluon bags model. The suggested model is solved analytically. It resolves a long standing problem of a unified description of the first and second order phase transition with the cross-over. Such an approach is necessary to model the complicated properties of quark-gluon plasma and hadronic matter from the first principles of statistical mechanics. In addition to the deconfinement phase transition, we found that at the curve of a zero surface tension coefficient there must exist the surface induced phase tranition of the 2-nd or higher order, which separates the pure quark gluon plasma (QGP) from the cross-over states. Thus, the present model predicts that the critical endpoint of quantum chromodynamics is the tricritical endpoint.

nucl-th↗
arXiv2007

Strange quark contributions to neutrino and antineutrino nucleus scattering via neutral current in quasi-elastic region

Strange quark contributions to the neutral current reaction in the neutrino scattering are investigated on the nucleon level and extended to the $^{12}$C target nucleus through the neutrino-induced knocked-out nucleon process in the quasi-elastic region within the framework of a relativistic single particle model. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino(antineutrino) scattering. Effects of the final state interaction for the knocked-out nucleon are included by a relativistic optical potential. We found that the sensitivity of the strange quark contents could be salient on the asymmetry between neutrino and antineutrino scattering cross sections. In specific, $A (ν({\bar ν}), ν^{'} ({\bar ν}^{'}) N)$ reaction is shown to be very sensitive test in the searches of the strangeness.

nucl-th↗
arXiv2008

Chromoelectric response functions for quark-gluon plasma

We determine the chromoelectric response of quark-gluon plasma (QGP) systematically within the framework of classical transport equations. The transport equations are set up in the phase space which includes the SU(3) group space corresponding to color (which is a dynamical degree of freedom), in addition to the position - momentum variables. The distribution functions are defined by projecting the density operators for the quarks and the gluons to their respective coherent states (defined over the extended phase space). The full import of the Yang-Mills(YM) dynamics is shown to manifest through the emergence of an intrinsic nonlinear, nonlocal response, whose behavior we determine in the long wavelength limit. It also manifests as a tensor response which is a characteristic of gluons. The response functions are shown to have a natural interpretation in terms of the renormalizations of the Abelian and the non-Abelian coupling constants. A detailed analysis of the screening of heavy quark potential and of the exact role played by the Debye mass screening in the case of the Cornell potential, is performed. We also discuss the non-Abelian contribution to Landau damping in QGP.

nucl-th↗
arXiv2007

The equation of state for the nuclear matter and the properties of the neutron star

The equation of state for the beta stable nuclear matter is calculated numerically, and then the Tolman-Oppenheimer-Volkov equation for the structure of the neutron star is solved in the fourth-order Runge-Kutta algorithm. It shows the mass and radius of the neutron star are functions of the central density of the neutron star and a maximum mass of 1.932 solar masses with a corresponding radius of 9.340km is obtained. Considering the equation of state of the nuclear matter must obey the causality, a new factor c is added in the nuclear potential energy formula. Therefore, with a new equation of state for the beta stable nuclear matter when c=0.15, a new maximum mass of 1.440 solar masses with a radius of 9.765km for the neutron star is obtained. Finally, the contribution of the cosmological constant to the structure of the neutron star is discussed, and we find the cosmological constant has minimal or negligible influence on the properties of the neutron star.

nucl-th↗
arXiv2009

Concavity for nuclear binding energies, thermodynamical functions and density functionals

Sequences of experimental ground-state energies for both odd and even $A$ are mapped onto concave patterns cured from convexities due to pairing and/or shell effects. The same patterns, completed by a list of excitation energies, give numerical estimates of the grand potential $Ω(β,μ)$ for a mixture of nuclei at low or moderate temperatures $T=β^{-1}$ and at many chemical potentials $μ.$ The average nucleon number $<{\bf A} >(β,μ)$ then becomes a continuous variable, allowing extrapolations towards nuclear masses closer to drip lines. We study the possible concavity of several thermodynamical functions, such as the free energy and the average energy, as functions of $<{\bf A} >.$ Concavity, which always occur for the free energy and is usually present for the average energy, allows easy interpolations and extrapolations providing upper and lower bounds, respectively, to binding energies. Such bounds define an error bar for the prediction of binding energies. Finally we show how concavity and universality are related in the theory of the nuclear density functional.

nucl-th↗
arXiv2007

Specific Density Of Binding Enerfy Of Core In Beta - Stable Nuclei is 2.57 MeV/fm^3

Recently an alpha-cluster model based on the pn-pair interactions with using the isospin invariance of nuclear force has been proposed. According to the model the excess neutron pairs fill out the free space in the core determined by the difference in the charge and matter radii of the alpha-clusters. Then the number of excess neutrons in beta-stable nuclei depends on the number of the core alpha-clusters. In such a representation the specific density of binding energy of core is the only parameter to fit the experimental binding energies of beta-stable nuclei and it turned out to be a constant value equal to 2.57 MeV/fm^3. Knowing the value allows one to estimate the size of a nucleus from its experimental binding energy.

nucl-th↗
arXiv2007

Quantization of Atomic and Nuclear Rest Masses

We were able to quantize phenomenologically the first time the atomic and nuclear rest masses. Note that this quantization rule is justified for atoms and nuclei with different A, N and Z and the nuclei and atoms represent a coherent synchronized systems -- a complex of coupled oscillators (resonators). The cooperative resonance synchronization mechanisms are responsible for explanation of how the electron volt world can influence the nuclear mega electron volt world. It means that we created new possibilities for inducing and controlling nuclear reactions by atomic processes.

physics.gen-ph↗
arXiv2007

Saturation of elliptic flow and shear viscosity

Effect of shear viscosity on elliptic flow is studied in causal dissipative hydrodynamics in 2+1 dimensions. Elliptic flow is reduced in viscous dynamics. Causal evolution of minimally viscous fluid ($η/s$=0.08), can explain the PHENIX data on elliptic flow in 16-23% Au+Au collisions up to $p_T\approx$3.6 GeV. In contrast, ideal hydrodynamics, can explain the same data only up to $p_T\approx$1.5 GeV. $p_T$ spectra of identified particles are also better explained in minimally viscous fluid than in ideal dynamics. However, saturation of elliptic flow at large $p_T$ is not reproduced.

nucl-th↗
arXiv2007

Pion freeze-out through HBT correlation in HICs from AGS/FAIR to RHIC energies

In this talk we present the results of two-pion HBT correlation at freeze-out in heavy ion collisions (HICs) from AGS to RHIC energies. The UrQMD hadron-string transport model as well as the CRAB analyzing program are adopted. Based on the cascade mode, in general, the calculations are satisfying and well in line with the experimental data although discrepancies are not negligible. Such as: I), the HBT time-related puzzle exists at all energies. II), at low AGS energies, the calculated volume as well as the mean free path of pion source at freeze-out are lower than data. It implies that a better description of interactions of particles at early stage of HICs is required.

nucl-th↗
arXiv2007

Relativistic Three-Body Scattering in a First Order Faddeev Formulation

Relativistic Faddeev equations for three-body scattering at arbitrary energies are solved in first order in the two-body transition operator in terms of momentum vectors without employing a partial wave decomposition. Relativistic invariance is incorporated within the framework of Poincar{é} invariant quantum mechanics. Based on a Malfliet-Tjon type interaction, observables for elastic and breakup scattering are calculated and compared to the nonrelativistic ones.

nucl-th↗
arXiv2007

The Tensor Part of the Skyrme Energy Density Functional

We systematically study the effect of the J^2 tensor terms in the Skyrme energy functional on properties of spherical nuclei. We build a set of 36 parameterizations covering a wide range of the corresponding parameter space. We analyze the impact of the tensor terms on the evolution of single-particle-level splittings along chains of semi-magic nuclei in spherical calculations. We find that positive values of the coupling constants of proton-neutron and like-particle tensor terms allow for a qualitative description of the evolution of neutron and proton single-particle level splittings in chains of Ca, Ni and Sn isotopes.

nucl-th↗
arXiv2007

Fluctuation of the initial condition from Glauber models

We analyze measures of the azimuthal asymmetry, in particular the participant harmonic moments, epsilon*, in a variety of Glauber-like models for the early stage of collisions at RHIC. Quantitative comparisons indicate substantial model dependence for epsilon*, reflecting different effective number of sources, while the dependence of the scaled standard deviation sigma(epsilon*)/epsilon* on the particular Glauber model is weak. For all the considered models the values of sigma(epsilon*)/epsilon* range from ~0.5 for the central collisions to ~0.3-0.4 for peripheral collisions. These values, dominated by statistics, change only by 10-15% from model to model. For central collisions and in the absence of correlations between the location of sources we obtain through the use of the central limit theorem the simple analytic formula sigma(epsilon*)/epsilon*(b=0) ~ \sqrt{4/pi-1} ~ 0.52$, independent on the collision energy, mass number, or the number of sources. We investigate the shape-fluctuation effects for jet quenching and find they are important only for very central events. Finally, we list some remarks and predictions from smooth hydrodynamics on higher flow coefficients and their fluctuations, in particular sigma(v_4)/v_4=2 sigma(v_2)/v_2.

nucl-th↗
arXiv2010

Tidal waves as yrast states in transitional nuclei

The yrast states of transitional nuclei are described as quadrupole waves running over the nuclear surface, which we call tidal waves. In contrast to a rotor, which generates angular momentum by increasing the angular velocity at approximately constant deformation, a tidal wave generates angular momentum by increasing the deformation at approximately constant angular velocity. The properties of the tidal waves are calculated by means of the cranking model in a microscopic way. The calculated energies and E2 transition probabilities of the yrast states in the transitional nuclides with $Z$= 44, 46, 48 and $N=56, 58, ..., 66$ reproduce the experiment in detail. The nonlinear response of the nucleonic orbitals results in a strong coupling between shape and single particle degrees of freedom.

nucl-th↗