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At least 145 records · Page 8Linked to original sources
arXiv2008

Viscosity and boost invariance at RHIC and LHC

We consider the longitudinal hydrodynamic evolution of the fireball created in a relativistic heavy-ion collision. Nonzero shear viscosity reduces the colling rate of the system and hinders the acceleration of the longitudinal flow. As a consequence, the initial energy density needed to reproduce the experimental data at RHIC energies is significantly reduced. At LHC energies, we expect that shear viscosity helps to conserve a Bjorken plateau in the rapidity distributions during the expansion.

nucl-th↗
arXiv2008

Unstable Quark-Gluon Plasma at LHC

Coupling of the quark-gluon plasma from the early stage of heavy-ion collisions is argued to be weaker at LHC than at RHIC. For this reason, the role of instabilities - the pre-equilibrium plasma is unstable with respect to chromomagnetic modes - will be enhanced. The instabilities isotropize the system and speed up the process of equilibration. A possibility to observe direct signals of the instabilities is considered.

nucl-th↗
arXiv2008

Light nuclei without a core

We introduce the no-core full configuration (NCFC) approach and present results for $^4$He, $^{12}$C and $^{14}$F with the realistic NN interaction, JISP16. We obtain ground state energies and their uncertainties through exponential extrapolations that we demonstrate are reliable in $^4$He where fully converged results are obtained. We find $^{12}$C is overbound by 1.7 MeV and we predict the yet-to-be-measured binding energy of $^{14}$F to be $68.1 \pm 2.7$ MeV. The extrapolated spectrum of $^{14}$F is in reasonable agreement with known features of the $^{14}$B spectrum.

nucl-th↗
arXiv2008

Soft-hadronic observables for relativistic heavy-ion collisions at RHIC and LHC

The relativistic hydrodynamics together with the single-freeze-out statistical hadronization model is used to describe the midrapidity hadron production in ultra-relativistic heavy-ion collisions at RHIC and LHC. At the highest RHIC energy our approach gives a quite satisfactory global description of soft hadronic observables including the HBT radii. With the increased initial energy, from RHIC to LHC, we expect the saturation of the pion elliptic flow and the moderate increase of the correlation radii.

nucl-th↗
arXiv2009

Neutrino masses from the GSI anomaly

We investigate the influence of the strong Coulomb field of a heavy nucleus on massive neutrinos, produced in the K-shell electron capture (EC) decays of the H-like 140Pr58+ and 142Pm60+ ions. The corrections to the neutrino masses due to virtually produced charged lepton W-boson pairs in the strong Coulomb field of a nucleus with charge Ze are calculated and discussed with respect to their influence on the period of the time-modulation of the number of daughter ions, observed recently in the EC-decays of the H-like 140Pr58+ and 142Pm60+ ions at GSI in Darmstadt. These corrections explain the 2.9 times higher difference of the squared neutrino masses obtained from the time-modulation of the EC-decays with respect to the value deduced from the antineutrino-oscillation experiments of KamLAND.

nucl-th↗
arXiv2008

High Energy Particles in the Solar Corona

Collective Ampere law interactions producing magnetic flux tubes piercing through sunspots into and then out of the solar corona allow for low energy nuclear reactions in a steady state and high energy particle reactions if a magnetic flux tube explodes in a violent event such as a solar flare. Filamentous flux tubes themselves are vortices of Ampere currents circulating around in a tornado fashion in a roughly cylindrical geometry. The magnetic field lines are parallel to and largely confined within the core of the vortex. The vortices may thereby be viewed as long current carrying coils surrounding magnetic flux and subject to inductive Faraday and Ampere laws. These laws set the energy scales of (i) low energy solar nuclear reactions which may regularly occur and (ii) high energy electro-weak interactions which occur when magnetic flux coils explode into violent episodic events such as solar flares or coronal mass ejections.

nucl-th↗
arXiv2008

Variations on a theme by Skyrme

We present a survey of the phenomenological adjustment of the parameters of the Skyrme-Hartree-Fock (SHF) model for a self-consistent description of nuclear structure and low-energy excitations. A large sample of reliable input data from nuclear bulk properties (energy, radii, surface thickness) is selected guided by the criterion that ground-state correlations should remain small. Least squares fitting techniques are used to determine the SHF parameters which accommodate best the given input data. The question of the predictive value of the adjustment is scrutinized by performing systematic variations with respect to chosen nuclear matter properties (incompressibility, effective mass, symmetry energy, and sum-rule enhancement factor). We find that the ground-state data, although representing a large sample, leave a broad range of choices, i.e. a broad range of nuclear matter properties. Information from giant resonances is added to pin down more precisely the open features. We then apply the set of newly adjusted parameterizations to several more detailed observables such as neutron skin, isotope shifts, and super-heavy elements. The techniques of least-squares fitting provide safe estimates for the uncertainties of such extrapolations. The systematic variation of forces allows to disentangle the various influences on a given observable and to estimate the predictive value of the SHF model. The results depend very much on the observable under consideration.

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arXiv2009

Reexamination for the calculation of elliptic flow and other fourier harmonics

We have argued that the azimuthal symmetry and asymmetry components in fourier expansion of particle momentum azimuthal distribution, $v_n$ (n=0, 1, 2, ...), should be calculated as an average of $cos(nϕ)$ first over particles in an event and then over events (event-wise average) rather than "an average over all particles in all events" (particle-wise average). In case of large centrality (multiplicity) bin the particle-wise average is not accurate because the influence (fluctuation) of particle multiplicity was not taken into account.

nucl-th↗
arXiv2009

Dynamical chiral symmetry breaking in strangelets at finite temperature

A model for strangelets at finite temperature is built, in which the quark masses are dynamically generated. The dynamical chiral symmetry breaking inside strangelets at finite temperature is investigated. It is found that the chiral symmetry is going to break spontaneously inside the strangelets at some finite temperature, and then the masses of strange quarks inside the strangelets increase as the temperature rises. The phenomenon that strange quark mass increases with temperature after the chiral symmetry breaks spontaneously is illustrated by some typical numerical examples.

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arXiv2009

Short-range correlations and shell structure of medium-mass nuclei

The single-particle spectrum of the two nuclei 133Sb and 101Sn is studied within the framework of the time-dependent degenerate linked-diagram perturbation theory starting from a class of onshell-equivalent realistic nucleon-nucleon potentials. These potentials are derived from the CD-Bonn interaction by using the so-called V-low-k approach with various cutoff momenta. The results obtained evidence the crucial role of short-range correlations in producing the correct 2s1d0g0h shell structure.

nucl-th↗
arXiv2008

On the Euler angles for the classical groups, Schwinger approach and Isoscalar factors for SU (3)

We establish recurrences formulas of the order of the classical groups that allow us to find a generalization of Euler's angles for classical groups and the invariant measures of these groups. We find the generating function for the SU(2) subset of SU(3) basis in the Fock-Bargmann space and a new basis of SU(3). This new basis is eigenfunction of the square of kinetic moment in product spaces of spherical harmonics. We generalize the generating function of SU (2) and we find invariant polynomials of SU (3) which are elements of the basis of SU (6). Using the above results we deduce the method of calculation isoscalar factors. We expose this method and we give the generating function for a particular case. Finally we determine the generating function of the elements of the representation matrix of SU(3) and we derive the analytical expression of these elements.

math-ph↗
arXiv2008

Medium polarization and finite size effects on the superfluidity of the inner crust of neutron stars

The 1S0 pairing gap associated with the inner crust of a neutron star is calculated, taking into account the coexistence of the nuclear lattice with the sea of free neutrons (finite size effects), as well as medium polarization effects associated with the exchange of density and spin fluctuations. Both effects are found to be important and to lead to an overall quenching of the pairing gap. This result, whose quantitative value is dependent on the effective interaction used to generate the single-particle levels, is a consequence of the balance between the attractive (repulsive) induced interaction arising from the exchange of density (spin) modes, balance which in turn is influenced by the presence of the protons and depends on the single-particle structure of the system.

nucl-th↗
arXiv2010

Relativistic mean-field theory applied to the study of neutron star properties

Nuclear physics can be applied in various ways to the study of neutron stars. This thesis reports on one such application, where the relativistic mean-field approximation has been employed to calculate the equations of state of matter in the neutron star interior. In particular the equations of state of nuclear and neutron star matter of the NL3, PK1 and FSUGold parameter sets were derived. A survey of available literature on neutron stars is presented and we use the derived equations of state to reproduce the properties of saturated nuclear matter as well as the mass-radius relationship of a static, spherical symmetric neutron star. Results are compared to published values of the properties of saturated nuclear matter and to available observational data of the mass-radius relationship of neutron stars.

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arXiv2008

Probing gluon shadowing with forward photons at RHIC

There is a major need to better constrain nuclear parton densities in order to provide reliable perturbative QCD predictions at the LHC as well as to probe possible non-linear evolution at small values of x. In these proceedings, we discuss how the production of prompt photons at large rapidity in p-p and d-Au collisions at RHIC (sqrt(s_NN)=200 GeV) is sensitive to the nuclear modifications of gluon distributions at x~0.001 and at rather low scales, Q^2~10 GeV^2. The nuclear production ratio, R_dAu=sigma(d+A->gamma+X)/(2A sigma(p+p->gamma X), is computed for isolated prompt photons at NLO using the nDSg nuclear parton densities, in order to assess the visibility of the signal. We also emphasise that the expected counting rates in a year of running at RHIC are large, indicating that R_dAu could be measured with a high statistical accuracy.

hep-ph↗
arXiv2008

Constraining the density dependence of nuclear symmetry energy with heavy-ion reactions and its astrophysical impact

Recent analyses of several isospin effects in heavy-ion reactions have allowed us to constrain the density dependence of nuclear symmetry energy at sub-saturation densities within a narrow range. Combined with constraints on the Equation of State (EOS) of symmetric nuclear matter obtained previously from analyzing the elliptic flow in relativistic heavy-ion collisions, the EOS of neutron-rich nuclear matter is thus partially constrained. Here we report effects of the partially constrained EOS of neutron-rich nuclear matter on the mass-radius correlation, moment of inertia, elliptical deformation and gravitational radiation of (rapidly) rotating neutron stars.

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arXiv2009

Microscopic approaches for nuclear Many-Body dynamics: applications to nuclear reactions

These lecture notes are addressed to PhD student and/or researchers who want a general overview of microscopic approaches based on mean-field and applied to nuclear dynamics. Our goal is to provide a good description of low energy heavy-ion collisions. We present both formal aspects and practical applications of the time-dependent Hartree-Fock (TDHF) theory. The TDHF approach gives a mean field dynamics of the system under the assumption that particles evolve independently in their self-consistent average field. As an example, we study the fusion of both spherical and deformed nuclei with TDHF. We also focus on nucleon transfer which may occur between nuclei below the barrier. These studies allow us to specify the range of applications of TDHF in one hand, and, on the other hand, its intrinsic limitations: absence of tunneling below the Coulomb barrier, missing dissipative effects and/or quantum fluctuations. Time-dependent mean-field theories should be improved to properly account for these effects. Several approaches, generically named "beyond TDHF" are presented which account for instance for pairing and/or direct nucleon-nucleon collisions. Finally we discuss recent progresses in exact ab-initio methods based on the stochastic mean-field concept.

nucl-th↗
arXiv2011

Lambda(1405,1/2^-) photoproduction from the gamma p -> K^+ Lambda(1405) reaction

We investigate the photoproduction of Lambda(1405,1/2^-) = Lambda* off the proton target using the effective Lagrangian in the Born approximation. We observed that, depending on the choice of the K* N Lambda* coupling strength, the total cross section becomes 0.1 <~ sigma_Lambda* <~ 0.2 mu b near the threshold and starts to decrease beyond E_gamma ~ 1.6 GeV, and the angular dependence shows a mild enhancement in the forward direction. It turns out that the energy dependence of the total cross section is similar to that shown in the recent LEPS experiment. This suggests that the production mechanism of the Lambda* is dominated by the s-channel contribution.

hep-ph↗