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Jinfeng Liao - One of the best experts on this subject based on the ideXlab platform.

Jeanpaul Blaizot - One of the best experts on this subject based on the ideXlab platform.

  • High gluon densities in heavy ion collisions
    Rept.Prog.Phys., 2017
    Co-Authors: Jeanpaul Blaizot
    Abstract:

    The early stages of heavy ion collisions are dominated by high density systems of Gluons that carry each a small fraction x of the momenta of the colliding nucleons. A distinguishing feature of such systems is the phenomenon of ‘saturation’ which tames the expected growth of the gluon density as the energy of the collision increases. The onset of saturation occurs at a particular transverse momentum scale, the ‘saturation momentum’, that emerges dynamically and that marks the onset of non-linear gluon interactions. At high energy, and for large nuclei, the saturation momentum is large compared to the typical hadronic scale, making high density Gluons amenable to a description with weak coupling techniques. This paper reviews some of the challenges faced in the study of such dense systems of small x Gluons, and of the progress made in addressing them. The focus is on conceptual issues, and the presentation is both pedagogical, and critical. Examples where high gluon density could play a visible role in heavy ion collisions are briefly discussed at the end, for illustration purpose.

  • gluon transport equation with effective mass and dynamical onset of bose einstein condensation
    Nuclear Physics, 2016
    Co-Authors: Jeanpaul Blaizot, Yin Jiang, Jinfeng Liao
    Abstract:

    Abstract We study the transport equation describing a dense system of Gluons, in the small scattering angle approximation, taking into account medium-generated effective masses of the Gluons. We focus on the case of overpopulated systems that are driven to Bose–Einstein condensation on their way to thermalization. The presence of a mass modifies the dispersion relation of the gluon, as compared to the massless case, but it is shown that this does not change qualitatively the scaling behavior in the vicinity of the onset.

  • Medium-induced gluon branching
    Journal of High Energy Physics, 2013
    Co-Authors: Edmond Iancu, Jeanpaul Blaizot, Fabio Dominguez, Yacine Mehtar-tani
    Abstract:

    We study the evolution of an energetic jet which radiates Gluons while propa- gating through a dense QCD medium modeled as a random distribution of color sources. Motivated by the heavy ion experimental program at the LHC, we focus on the medium- induced radiation of (relatively) soft Gluons, which are abundantly emitted at large angles and thus can transport a small fraction of the jet energy far away from the jet axis. We perform a complete calculation of the medium-induced gluon branching in the regime where the Gluons that take part in the branching undergo multiple soft scattering with the medium. We extend the BDMPSZ theory of radiative energy loss by including the trans- verse momentum dependence in the kernel that describes the branching and by analyzing the correlations between the two ospring Gluons. We demonstrate that these Gluons lose color coherence with respect to each other over a time scale that is comparable to the duration of the branching. It follows that interference eects between successive emissions are suppressed, a necessary ingredient for a description of multiple emission of soft Gluons by a probabilistic, branching process.

Jean-françois Colonna - One of the best experts on this subject based on the ideXlab platform.

E. Sokatchev - One of the best experts on this subject based on the ideXlab platform.

  • on planar gluon amplitudes wilson loops duality
    Nuclear Physics, 2008
    Co-Authors: James M Drummond, G. P. Korchemsky, Johannes M Henn, E. Sokatchev
    Abstract:

    There is growing evidence that on-shell gluon scattering amplitudes in planar N=4 SYM theory are equivalent to Wilson loops evaluated over contours consisting of straight, light-like segments defined by the momenta of the external Gluons. This equivalence was first suggested at strong coupling using the AdS/CFT correspondence and has since been verified at weak coupling to one loop in perturbation theory. Here we perform an explicit two-loop calculation of the Wilson loop dual to the four-gluon scattering amplitude and demonstrate that the relation holds beyond one loop. We also propose an anomalous conformal Ward identity which uniquely fixes the form of the finite part (up to an additive constant) of the Wilson loop dual to four- and five-gluon amplitudes, in complete agreement with the BDS conjecture for the multi-gluon MHV amplitudes

  • The hexagon Wilson loop and the BDS ansatz for the six-gluon amplitude
    2008
    Co-Authors: J. M. Drummond, J. Henn, G. P. Korchemsky, E. Sokatchev
    Abstract:

    As a test of the gluon scattering amplitude/Wilson loop duality, we evaluate the hexagonal light-like Wilson loop at two loops in N=4 super Yang-Mills theory. We compare its finite part to the Bern-Dixon-Smirnov (BDS) conjecture for the finite part of the six-gluon amplitude. We find that the two expressions have the same behavior in the collinear limit, but they differ by a non-trivial function of the three (dual) conformally invariant variables. This implies that either the BDS conjecture or the gluon amplitude/Wilson loop duality fails for the six-gluon amplitude, starting from two loops. Our results are in qualitative agreement with the analysis of Alday and Maldacena of scattering amplitudes with infinitely many external Gluons.

  • On planar gluon amplitudes/Wilson loops duality
    2007
    Co-Authors: J. M. Drummond, J. Henn, G. P. Korchemsky, E. Sokatchev
    Abstract:

    There is growing evidence that on-shell gluon scattering amplitudes in planar N=4 SYM theory are equivalent to Wilson loops evaluated over contours consisting of straight, light-like segments defined by the momenta of the external Gluons. This equivalence was first suggested at strong coupling using the AdS/CFT correspondence and has since been verified at weak coupling to one loop in perturbation theory. Here we perform an explicit two-loop calculation of the Wilson loop dual to the four-gluon scattering amplitude and demonstrate that the relation holds beyond one loop. We also propose an anomalous conformal Ward identity which uniquely fixes the form of the finite part (up to an additive constant) of the Wilson loop dual to four- and five-gluon amplitudes, in complete agreement with the BDS conjecture for the multi-gluon MHV amplitudes.

Dirk H Rischke - One of the best experts on this subject based on the ideXlab platform.

  • debye screening and the meissner effect in a two flavor color superconductor
    Physical Review D, 2000
    Co-Authors: Dirk H Rischke
    Abstract:

    I compute the gluon self-energy in a color superconductor with two flavors of massless quarks, where condensation of Cooper pairs breaks SU(3){sub c} to SU(2){sub c}. At zero temperature, there is neither Debye screening nor a Meissner effect for the three Gluons of the unbroken SU(2){sub c} subgroup. The remaining five Gluons attain an electric as well as a magnetic mass. For temperatures approaching the critical temperature for the onset of color superconductivity, or for gluon momenta much larger than the color-superconducting gap, the self-energy assumes the form given by the standard hard-dense loop approximation. The gluon self-energy determines the coefficient of the kinetic term in the effective low-energy theory for the condensate fields. (c) 2000 The American Physical Society.

  • debye screening and the meissner effect in a three flavor color superconductor
    Physical Review D, 2000
    Co-Authors: Dirk H Rischke
    Abstract:

    I compute the gluon self-energy in a color superconductor with three flavors of massless quarks, where condensation of Cooper pairs breaks the color and flavor SU(3){sub c}xU(3){sub V}xU(3){sub A} symmetry of QCD to the diagonal subgroup SU(3){sub c+V}. At zero temperature, all eight electric Gluons obtain a Debye screening mass, and all eight magnetic Gluons a Meissner mass. The Debye as well as the Meissner masses are found to be equal for the different gluon colors. These masses determine the coefficients of the kinetic terms in the effective theory for the low-energy degrees of freedom. Their values agree with those obtained by Son and Stephanov. (c) 2000 The American Physical Society.

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