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Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 23: Plenar

HK 23.3: Group Report

Tuesday, March 17, 1998, 12:30–13:00, P

Quantum Transport of Particles with Finite Mass Width — •J. Knoll1, Y.B. Ivanov2,1, and D.N. Voskresenski3,11Gesellschaft für Schwerionenforschung mbH, Planckstr. 1, 64291 Darmstadt — 2Kurchatov Inst. Moscow — 3MIPE Moscow

Within non-equilibrium quantum field theory we derive transport equations which take due account of the damping width Γ of the particles in dense matter [1]. The picture goes beyond common transport schemes. It unifies the description of resonances, which have a width already in vacuum, with all other particles, which obtain a widths from collision, decay or creation processes in matter. It accounts for quantum coherence features that strongly modify the in-medium rates, in particular for the soft modes with energies and momenta comparable or smaller than the scale set by the damping Γ [2]. Likewise polarization effects in terms of drag and back flow or time delays are included. The resulting dynamical equations are conserving and thermodynamically consistent. If not applicable immediately, the theory permits adequate and consistent quantum improvements of the in-medium rates in transport simulation codes presently applied to high energy nuclear collisions.

The derivation starts from the Kadanoff - Baym equations for the Wigner functions W(x,p) in four-space x and four-momentum p of the various degrees of freedom. A closed set of transport equations is obtained consistent to first order gradient approximation. The latter restricts the application to slowly varying changes of the distribution functions, both in space and time, and yet contains at least all the quantum features of the corresponding equilibrium scheme. In particular the common zero mass width (quasi-particle) approximation is avoided! Therefore, besides the real part of the self-energies, the imaginary parts, i.e. the damping widths Γ, are included in self consistent way. Within the Φ-functional method of Baym the scheme can be closed at any desired loop order of the generating functional defining a conserving and thermodynamically consistent effective theory. Besides the dynamical equations "local" algebraic Dyson equations emerge to determine the spectral functions. The corresponding diagrammatic rules for the source terms and the gain and loss rates in the transport equations are derived.
[1] Y. Ivanov, J. Knoll, D. N. Voskresensky: in preparation for Phys. Rep. C;
[2] J. Knoll, D. N. Voskresensky, Ann. Phys. 249 (1996) 532.

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