5,131 research outputs found
Jet Quenching
A short summary of the physics underlying jet quenching is givenComment: 10 pages, LaTex, 11 postscript figures, Proceedings of Quark Matter
2002, Nantes, France, July 18-24, 200
Perturbative Hot Gauge Theories - Recent Results
Current results in high temperature gauge theories obtained in the context of
the perturbative method of resumming hard thermal loops are reviewed. Beyond
leading order properties of the gluon excitation, and the recent
(controversial) calculations of the damping rates are discussed. QCD
predictions on plasma signatures are exemplified by the thermal production
rates of energetic as well as soft photons. [Talk given at the 3rd Workshop on
Thermal Field Theories and their Applications, August 15--27, 1993, Banff,
Alberta, Canada]Comment: 11 pages, typeset using LATEX, BI-TP 93/6
Stopping distance for high energy jets in weakly-coupled quark-gluon plasmas
We derive a simple formula for the stopping distance for a high-energy quark
traveling through a weakly-coupled quark gluon plasma. The result is given to
next-to-leading-order in an expansion in inverse logarithms ln(E/T), where T is
the temperature of the plasma. We also define a stopping distance for gluons
and give a leading-log result. Discussion of stopping distance has a
theoretical advantage over discussion of energy loss rates in that stopping
distances can be generalized to the case of strong coupling, where one may not
speak of individual partons.Comment: 20 pages, 4 figures [change from v1: fixed embarrassing reference
error
Deciphering the properties of the medium produced in heavy ion collisions at RHIC by a pQCD analysis of quenched large spectra
We discuss the question of the relevance of perturbative QCD calculations for
analyzing the properties of the dense medium produced in heavy ion collisions.
Up to now leading order perturbative estimates have been worked out and
confronted with data for quenched large hadron spectra. Some of
them are giving paradoxical results, contradicting the perturbative framework
and leading to speculations such as the formation of a strongly interacting
quark-gluon plasma. Trying to bypass some drawbacks of these leading order
analysis and without performing detailed numerical investigations, we collect
evidence in favour of a consistent description of quenching and of the
characteristics of the produced medium within the pQCD framework.Comment: 10 pages, 3 figure
On the string-inspired approach to QED in external field
Strassler's formulation of the string-derived Bern-Kosower formalism is
extended to consider QED processes in homogeneous constant external field. A
compact expression for the contribution of the one-loop with arbitrary number
of external photon lines is given for scalar QED. Extension to spinor QED is
shortly discussed.Comment: 14 pages,Revtex,no figure
Comparison of theory with experiment for positron production from high-energy electrons moving along crystal axes
Various positron distributions are obtained using an approach developed
earlier for the description of electron-photon showers in axially aligned
single crystals. Based on these distributions, characteristics of the positron
yield measured in recent experiments are calculated. Theoretical estimations
display a rather good agreement with experimental results obtained using 3 to
10 GeV electrons aligned to the - axis of the tungsten crystals.Comment: 10 pages, 6 Postscript figure
On the Angular Dependence of the Radiative Gluon Spectrum
The induced momentum spectrum of soft gluons radiated from a high energy
quark produced in and propagating through a QCD medium is reexamined in the
BDMPS formalism. A mistake in our published work (Physical Review C60 (1999)
064902) is corrected. The correct dependence of the fractional induced loss
as a universal function of the variable
where is the size of the medium and
the transport coefficient is presented. We add the proof that the
radiated gluon momentum spectrum derived in our formalism is equivalent with
the one derived in the Zakharov-Wiedemann approach.Comment: LaTex, 5 pages, 1 figur
Angular Dependence of the Radiative Gluon Spectrum and the Energy Loss of Hard Jets in QCD Media
The induced momentum spectrum of soft gluons radiated from a high energy
quark propagating through a QCD medium is derived in the BDMPS formalism. A
calorimetric measurement for the medium dependent energy lost by a jet with
opening angle is proposed.The fraction of this energy
loss with respect to the integrated one appears to be the relevant
observable.It exhibits a universal behaviour in terms of the variable
where is the size of the medium and
the transport coefficient. Phenomenological implications for the
differences between cold and hot QCD matter are discussed.Comment: 13 pages and 7 figures, RevTe
On p_T-broadening of high energy partons associated with the LPM effect in a finite-volume QCD medium
We study the contributions from radiation to -broadening of a high
energy parton traversing a QCD medium with a finite length . The interaction
between the parton and the medium is described by decorrelated static multiple
scattering. Amplitudes of medium-induced gluon emission and parton self-energy
diagrams are evaluated in the soft gluon limit in the BDMPS formalism. We find
both the double-logarithmic correction from incoherent scattering, which is
parametrically the same as that in single scattering, and the logarithmic
correction from the LPM effect. Therefore, we expect a parametrically large
correction from radiation to the medium-induced -broadening in
perturbative QCD.Comment: 19 pages, focusing only on calculations about the medium-induced
diagrams, origin for double-log reinterpreted, final version to appear in
JHE
How does transverse (hydrodynamic) flow affect jet-broadening and jet-quenching ?
We give the modification of formulas for -broadening and energy
loss which are necessary to calculate parton interactions in a medium with
flow. Arguments are presented leading to the conclusion that for large
-spectra observed in heavy ion collisions at RHIC, the influence of
transverse flow on the determination of the "quenching power" of the produced
medium is small. This leaves open the question of the interpretation of data in
a consistent perturbative framework.Comment: 8 pages and 4 figures; version v2 includes more consistent notations
and correction of fig.2; version v3 contains a misprint correction, an added
sentence in section 3C and in the Introduction as well as in section 4 a
rephrasing of comments about references [31,32,35
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