Rescattering Effects in Quarkonium Production

We study eta_c and J/psi hadroproduction induced by multiple scattering off fixed centres in the target. We determine the minimum number of hard scatterings required and show that additional soft scatterings may be factorized, at the level of the production amplitude for the eta_c and of the cross section for the J/psi. The J/psi provides an interesting example of soft rescattering effects occurring inside a hard vertex. We also explain the qualitative difference between the transverse momentum broadening of the J/psi and of the Upsilon observed in collisions on nuclei. We point out that rescattering from spectators produced by beam and target parton evolution may have important effects in J/psi production.Comment: 30 pages, Late

Finite Volume Solution of 2D and 3D Euler and Navier-Stokes Equations

This contribution deals with the modern finite volume schemes solving the Euler and Navier-Stokes equations for transonic flow problems. We will mention the TVD theory for first order and higher order schemes and some numerical examples obtained by 2D central and upwind schemes for 2D transonic flows in the GAMM channel or through the SE 1050 turbine cascade of Skoda Plzen. In the next part two new 2D finite volume schemes are presented. Explicit composite scheme on a structured triangular mesh and implicit scheme realized on a general unstructured mesh. Both schemes are used for the solution of inviscid transonic flows in the GAMM channel and the implicit scheme also for the flows through the SE 1050 turbine cascade using both triangular and quadrilateral meshes. For the case of the flows through the SE 1050 turbine we compare the numerical results with the experiment. The TVD MacCormack method as well as a finite volume composite scheme are extended to a 3D method for solving flows through channels and turbine cascades. 1. Mathematical model We consider the system of 2D Navier-Stokes equations for compressible medium in conservative form: W t + F x +G y = R x + S y , W = [#, #u, #v, e], p = (# #(u F = [#u, #u + p, #uv, (e + p)u], G = [#v, #uv, #v + p, (e + p)v], R = [0, # 11 , # 12 , u# 11 + v# 12 + kT x ], S = [0, # 21 , # 22 , u# 21 + v# 22 + kT y ], (1) where # is the density, (u, v) the velocity vector, e the total energy per unit volume, the viscosity coe#cient, k is the heat conductivity, p is the pressure, # is the adiabatic coe#cient, and the components of the stress tensor # are # 11 = u x , # 21 = # 12 = (u y + v x ) , # 22 = u x + 4 . (2) The 2D Euler equations are obtained from the Navier-Stokes equations by..