Parton distribution amplitudes of light vector mesons

Fei Gao, Lei Chang, Yu-Xin Liu, Craig D. Roberts, Sebastian M. Schmidt

A rainbow-ladder truncation of QCD’s Dyson-Schwinger equations is used to calculate rho- and phi-meson valence-quark (twist-two parton) distribution amplitudes (PDAs) via a light-front projection of their Bethe-Salpeter wave functions, which possess S- and D-wave components of comparable size in the meson rest frame. All computed PDAs are broad concave functions, whose dilation with respect to the asymptotic distribution is an expression of dynamical chiral symmetry breaking. The PDAs can be used to define an ordering of valence-quark light-front spatial-extent within mesons: this size is smallest within the pion and increases through the perp-polarisation to the parallel-polarisation of the vector mesons; effects associated with the breaking of SU(3)-flavour symmetry are significantly smaller than those associated with altering the polarisation of vector mesons. Notably, the predicted pointwise behaviour of the rho-meson PDAs is in quantitative agreement with that inferred recently via an analysis of diffractive vector-meson photoproduction experiments.

Subjects: Nuclear Theory (nucl-th); High Energy Physics – Experiment (hep-ex); High Energy Physics – Lattice (hep-lat); High Energy Physics – Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
Cite as: arXiv:1405.0289 [nucl-th]

Towards an optical potential for rare-earths through coupled channels

G. P. A. Nobre, F. S. Dietrich, M. Herman, A. Palumbo, S. Hoblit, D. Brown

The coupled-channel theory is a natural way of treating nonelastic channels, in particular those arising from collective excitations, defined by nuclear deformations. Proper treatment of such excitations is often essential to the accurate description of reaction experimental data. Previous works have applied different models to specific nuclei with the purpose of determining angular-integrated cross sections. In this work, we present an extensive study of the effects of collective couplings and nuclear deformations on integrated cross sections as well as on angular distributions in a consistent manner for neutron-induced reactions on nuclei in the rare-earth region. This specific subset of the nuclide chart was chosen precisely because of a clear static deformation pattern. We analyze the convergence of the coupled-channel calculations regarding the number of states being explicitly coupled. Inspired by the work done by Dietrich \emph{et al.}, a model for deforming the spherical Koning-Delaroche optical potential as function of quadrupole and hexadecupole deformations is also proposed. We demonstrate that the obtained results of calculations for total, elastic and inelastic cross sections, as well as elastic and inelastic angular distributions correspond to a remarkably good agreement with experimental data for scattering energies above around a few MeV.

Cite as: arXiv:1311.1735 [nucl-th]
(or arXiv:1311.1735v1 [nucl-th] for this version)

3+1 dimensional viscous hydrodynamics at high baryon densities

Iu. Karpenko, M. Bleicher, P. Huovinen, H. Petersen

We apply a 3+1D viscous hydrodynamic + cascade model to the heavy ion collision reactions with √sNN=6.339 GeV. To accommodate the model for a given collision energy range, the initial conditions for hydrodynamic phase are taken from UrQMD, and the equation of state at finite baryon density is based on Chiral model coupled to the Polyakov loop.
We study the collision energy dependence of pion and kaon rapidity distributions and mT-spectra, as well as charged hadron elliptic flow and how shear viscosity affects them. The model calculations are compared to the data for Pb-Pb collisions at CERN SPS, as well as for Au-Au collisions in the Beam Energy Scan (BES) program energies at BNL RHIC. The data favours the value of shear viscosity η/s0.2 for this collision energy range.

Cite as: arXiv:1311.0133 [nucl-th]
  (or arXiv:1311.0133v1 [nucl-th] for this version)

Skyrme functional from a three-body pseudo-potential of second-order in gradients. Formalism for central terms

J. Sadoudi, T. Duguet, J. Meyer, M. Bender

Description:In one way or the other, all modern parametrizations of the nuclear energy density functional (EDF) do not respect the exchange symmetry associated with Pauli’s principle. It has been recently shown that this practice jeopardizes multi-reference (MR) EDF calculations by contaminating the energy with spurious self-interactions that, for example, lead to finite steps or even divergences when plotting it as a function of collective coordinates. As of today, the only viable option to bypass these pathologies is to rely on EDF kernels that enforce Pauli’s principle from the outset by strictly and exactly deriving from a genuine, i.e. density-independent, Hamilton operator.
We wish to develop the most general Skyrme-like EDF parametrization containing linear, bilinear and trilinear terms in the density matrices with up to two gradients, under the key constraint that it derives strictly from an effective Hamilton operator. The most general three-body Skyrme-like pseudo-potential containing up to two gradient operators is constructed to generate the trilinear part. The present study is limited to central terms. Spin-orbit and tensor will be addressed in a forthcoming paper.

Cite as:
arXiv:1310.0854 [nucl-th]
(or arXiv:1310.0854v1 [nucl-th] for this version)

Calculations of three-nucleon reactions with N3LO chiral forces: achievements and challenges

Henryk Witala, Jacek Golak, Roman Skibinski, Kacper Topolnicki


We discuss the application of the chiral N3LO forces to three-nucleon reactions and point to the challenges which will have to be addressed. Present approaches to solve three-nucleon Faddeev equations are based on a partial-wave decomposition. A rapid increase of the number of terms contributing to the chiral three-nucleon force when increasing the order of the chiral expansion from N2LO to N3LO forced us to develop a fast and effective method of automatized partial wave decomposition. At low energies of the incoming nucleon below about 20MeV, where only a limited number of partial waves is required, this method allowed us to perform calculations of reactions in the three-nucleon continuum using N3LO two- and three-nucleon forces. It turns out that inclusion of consistent chiral interactions, with relativistic 1/m corrections and short-range 2pi-contact term omitted in the N3LO three-nucleon force, does not explain the long standing low energy Ay-puzzle. We discuss problems arising when chiral forces are applied at higher energies, where large three-nucleon force effects are expected. It seems plausible that at higher energies, due to a rapid increase of a number of partial waves required to reach convergent results, a three-dimensional formulation of the Faddeev equations which avoids partial-wave decomposition is desirable.

Cite as:
arXiv:1310.0198 [nucl-th]
(or arXiv:1310.0198v1 [nucl-th] for this version)