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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. Voskresenski3,1 — 1Gesellschaft 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.