3,684 research outputs found
Anomalous mass dependence of radiative quark energy loss in a finite-size quark-gluon plasma
We demonstrate that for a finite-size quark-gluon plasma the induced gluon
radiation from heavy quarks is stronger than that for light quarks when the
gluon formation length becomes comparable with (or exceeds) the size of the
plasma. The effect is due to oscillations of the light-cone wave function for
the in-medium transition. The dead cone model by Dokshitzer and
Kharzeev neglecting quantum finite-size effects is not valid in this regime.
The finite-size effects also enhance the photon emission from heavy quarks.Comment: 8 pages, 3 figure
Non-linear effects in hopping conduction of single-crystal La_{2}CuO_{4 + \delta}
The unusual non-linear effects in hopping conduction of single-crystal
La_{2}CuO_{4 + \delta} with excess oxygen has been observed. The resistance is
measured as a function of applied voltage U (10^{-3} V - 25 V) in the
temperature range 5 K 0.1 V) the
conduction of sample investigated corresponds well to Mott's variable-range
hopping (VRH). An unusual conduction behavior is found, however, in low voltage
range (approximately below 0.1 V), where the influence of electric field and
(or) electron heating effect on VRH ought to be neglected. Here we have
observed strong increase in resistance at increasing U at T < 20 K, whereas at
T > 20 K the resistance decreases with increasing U. The magnetoresistance of
the sample below 20 K has been positive at low voltage and negative at high
voltage. The observed non-Ohmic behavior is attributable to inhomogeneity of
the sample, and namely, to the enrichment of sample surface with oxygen during
the course of the heat treatment of the sample in helium and air atmosphere
before measurements. At low enough temperature (below 20 K) the surface layer
with increased oxygen concentration is presumed to consist of disconnected
superconducting regions (with T_{c} about 20 K) in poor-conducting matrix. The
results obtained demonstrate that transport properties of cuprate oxides may be
determined in essential degree by structural or stoichimetric inhomogeneities.
This should be taken into account at evaluation of "quality" of
high-temperature superconductors on the basis of transport properties
measurements.Comment: 12 pages, REVTex, 11 Postscript figures, To be published in Fizika
Nizkikh Temperatur (published by AIP as Low Temperature Physics
Radiative parton energy loss and jet quenching in high-energy heavy-ion collisions
We study within the light-cone path integral approach [3] the effect of the
induced gluon radiation on high-p_{T} hadrons in high-energy heavy-ion
collisions. The induced gluon spectrum is represented in a new form which is
convenient for numerical simulations. For the first time, computations are
performed with a realistic parametrization of the dipole cross section. The
results are in reasonable agreement with suppression of high-p_{T} hadrons in
Au+Au collisions at \sqrt{s}=200 GeV observed at RHIC.Comment: 12 pages, 3 epsi figures. Typos correcte
Azimuthal asymmetry as a new handle on in diffractive DIS
We propose a new method of the determination of
from the dependence of the diffractive
cross section on the azimuthal angle between the electron scattering and proton
scattering planes. The method is based on our finding of the model independence
of the ratio of the interference and transverse diffractive structure
functions. The predicted azimuthal asymmetry is substantial and can be measured
at HERA. We show that the accuracy of our reconstruction of is adequate
for a reliable test of an important pQCD prediction of R^{D}\gsim 1 for large
.Comment: 5 pages, 6 figure
Transverse Spectra of Radiation Processes in Medium
We develop a formalism for evaluation of the transverse momentum dependence
of cross sections of the radiation processes in medium. The analysis is based
on the light-cone path integral approach to the induced radiation. The results
are applicable in both QED and QCD
Final state interaction effects in scattering
We present a systematic study of the final-state interaction (FSI) effects in
scattering in the CEBAF energy range with particular emphasis on the
phenomenon of the angular anisotropy of the missing momentum distribution. We
find that FSI effects dominate at missing momentum p_m \gsim 1.5 fm.
FSI effects in the excitation of the -wave state are much stronger than in
the excitation of the -wave.Comment: LATEX, 11 pages, 5 figures available from the authors on request,
KFA-IKP(TH)-1994-3
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