4,748 research outputs found
Collisional Energy Loss of Fast Charged Particles in Relativistic Plasmas
Following an argument by Kirzhnits we rederive an exact expression for the
energy loss of a fast charged particle in a relativistic plasma using the
quantum field theoretical language. We compare this result to perturbative
calculations of the collisional energy loss of an energetic electron or muon in
an electron-positron plasma and of an energetic parton in the quark-gluon
plasma.Comment: 9 pages, LATEX, 2 PostScript figure
Flow dependence of high parton energy loss in heavy-ion collisions
The measured transverse momentum spectra and HBT correlations of bulk (i.e.
low ) matter can be well explained by assuming that the soft sector of
particles produced in ultrarelativistic heavy-ion collisions is (approximately)
thermalized and undergoes collective accelerated expansion in both longitudinal
and transverse direction. However, this implies that bulk matter will have a
non-vanishing flow component transverse to the trajectory of a high
partonic jets. In general, this will increase the energy loss experienced by
the jet parton and modify the shape of the jet cone. In this paper, we present
a systematic study of the magnitude of the additional energy loss induced by
flow under realistic assumptions for the medium evolution. We argue that a
perturbative QGP description may be sufficient for the measured if
flow during the medium evolution is taken into account properly
Structure Functions and Pair Correlations of the Quark-Gluon Plasma
Recent experiments at RHIC and theoretical considerations indicate that the
quark-gluon plasma, present in the fireball of relativistic heavy-ion
collisions, might be in a liquid phase. The liquid state can be identified by
characteristic correlation and structure functions. Here definitions of the
structure functions and pair correlations of the quark-gluon plasma are
presented as well as perturbative results. These definitions might be useful
for verifying the quark-gluon-plasma liquid in QCD lattice calculations.Comment: 9 pages, 1 figure, revised version (new remark on the coupling
parameter on page 2), to be published in Phys. Rev.
Collective Excitations of Supersymmetric Plasma
Collective excitations of N = 1 supersymmetric electromagnetic plasma are
studied. Since the Keldysh-Schwinger approach is used, not only equilibrium but
also non-equilibrium plasma, which is assumed to be ultrarelativistic, is under
consideration. The dispersion equations of photon, photino, electron and
selectron modes are written down and the self-energies, which enter the
equations, are computed in the Hard Loop Approximation. The self-energies are
discussed in the context of effective action which is also given. The photon
modes and electron ones appear to be the same as in the usual ultrarelativistic
plasma of electrons, positrons and photons. The photino modes coincide with the
electron ones and the selectron modes are as of free relativistic massive
particle.Comment: 14 pages, typos corrected, Phys. Rev. D in prin
What can we learn from electromagnetic plasmas about the quark-gluon plasma?
Ultra-relativistic electromagnetic plasmas can be used for improving our
understanding of the quark-gluon plasma. In the weakly coupled regime both
plasmas can be described by transport theoretical and quantum field theoretical
methods leading to similar results for the plasma properties (dielectric
tensor, dispersion relations, plasma frequency, Debye screening, transport
coefficients, damping and particle production rates). In particular, future
experiments with ultra-relativistic electron-positron plasmas in ultra-strong
laser fields might open the possibility to test these predictions, e.g. the
existence of a new fermionic plasma wave (plasmino). In the strongly coupled
regime electromagnetic plasmas such as complex plasmas can be used as models or
at least analogies for the quark-gluon plasma possibly produced in relativistic
heavy-ion experiments. For example, pair correlation functions can be used to
investigate the equation of state and cross section enhancement for parton
scattering can be explained.Comment: 8 pages, 7 figures, talk given at the SCCS 2008 International
Conference, 29 July - 2 August 2008, Camerino, Ital
Ward Identities in Non-equilibrium QED
We verify the QED Ward identity for the two- and three -point functions at
non-equilibrium in the HTL limit. We use the Keldysh formalism of real time
finite temperature field theory. We obtain an identity of the same form as the
Ward identity for a set of one loop self-energy and one loop three-point vertex
diagrams which are constructed from HTL effective propagators and vertices.Comment: 19 pages, RevTex, 4 PostScript figures, revised version to be
published in Phys. Rev.
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