2,624 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
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
Self-Protection of Massive Cosmological Gravitons
Relevant deformations of gravity present an exciting window of opportunity to
probe the rigidity of gravity on cosmological scales. For a single-graviton
theory, the leading relevant deformation constitutes a graviton mass term. In
this paper, we investigate the classical and quantum stability of massive
cosmological gravitons on generic Friedman backgrounds. For a Universe
expanding towards a de Sitter epoch, we find that massive cosmological
gravitons are self-protected against unitarity violations by a strong coupling
phenomenon.Comment: 1+11 pages, v2: references adde
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
Collinear Photon Emission from the Quark-Gluon Plasma: The Light-Cone Path Integral Formulation
We give a simple physical derivation of the photon emission rate from the
weakly coupled quark-gluon plasma connected with the collinear processes and . The analysis is based on the light-cone
path integral approach to the induced radiation. Our results agree with that by
Arnold, Moore and Yaffe obtained using the real-time thermal perturbation
theory. It is demonstrated that the solution of the AMY integral equation is
nothing but the time-integrated Green's function of the light-cone path
integral approach written in the momentum representation.Comment: 12 pages, 2 figure
Fully quantum treatment of the Landau--Pomeranchuk--Migdal effect in QED and QCD
For the first time a rigorous quantum treatment of the
Landau-Pomeranchuk-Migdal effect in QED and QCD is given. The rate of photon
(gluon) radiation by an electron (quark) in medium is expressed through the
Green's function of a two-dimensional Schr\"odinger equation with an imaginary
potential. In QED this potential is proportional to the dipole cross section
for scattering of pair off an atom, in QCD it is proportional to
the cross section of interaction with color centre of the color singlet
quark-antiquark-gluon system.Comment: E-mail: [email protected], [email protected]
The Riemann-Hilbert problem associated with the quantum Nonlinear Schrodinger equation
We consider the dynamical correlation functions of the quantum Nonlinear
Schrodinger equation. In a previous paper we found that the dynamical
correlation functions can be described by the vacuum expectation value of an
operator-valued Fredholm determinant. In this paper we show that a
Riemann-Hilbert problem can be associated with this Fredholm determinant. This
Riemann-Hilbert problem formulation permits us to write down completely
integrable equations for the Fredholm determinant and to perform an asymptotic
analysis for the correlation function.Comment: 21 pages, Latex, no figure
Parton energy loss in an expanding quark-gluon plasma: Radiative vs collisional
We perform a comparison of the radiative and collisional parton energy losses
in an expanding quark-gluon plasma. The radiative energy loss is calculated
within the light-cone path integral approach. The collisional energy loss is
calculated using the Bjorken method with an accurate treatment of the binary
collision kinematics. Our numerical results demonstrate that for RHIC and LHC
conditions the collisional energy loss is relatively small in comparison to the
radiative one. We find an enhancement of the heavy quark radiative energy loss
as compared to that of the light quarks at high energies.Comment: 13 pages, 3 figure
Jet quenching with running coupling including radiative and collisional energy losses
We calculate the nuclear modification factor for RHIC and LHC conditions
accounting for the radiative and collisional parton energy loss with the
running coupling constant.We find that the RHIC data can be explained both in
the scenario with the chemically equilibrium quark-gluon plasma and purely
gluonic plasma with slightly different thermal suppression of the coupling
constant. The role of the parton energy gain due to gluon absorption is also
investigated. Our results show that the energy gain gives negligible effect.Comment: 11 pages, 3 figure
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