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Nuclear Theory·nucl-th

Wednesday·March 25, 2015

13 papers—9 primary·4 cross-listed

All13Primary9Cross-lists4
  1. 10

    [Submitted on 24 Mar 2015] (cross-list from hep-ph)

    Jet asymmetry and momentum imbalance from and partonic processes in relativistic heavy-ion collisions

    Alejandro Ayala (Cape Town U. & Cape Town U., Dept. Math. & Mexico U., ICN)🇲🇽 · Isabel Dominguez (FCFM, Sinaloa U.)🇲🇽 · Jamal Jalilian-Marian (Baruch Coll.)🇺🇸 · Maria Elena Tejeda-Yeomans (Sonora U. & Mexico U., ICN)🇲🇽

    We study momentum imbalance as a function of jet asymmetry in high-energy heavy-ion collisions. To implement parton production during the collision, we include all Leading Order (LO) and parton processes in pQCD. The produced partons lose energy within the quark gluon plasma and hadronize collinearly when they leave it. The energy and momentum deposited into the plasma is described using linear viscous hydrodynamics with a constant energy loss per unit length and a total energy loss given by a Gaussian probability centered around a mean value and a half-width . We argue that the shape of the asymmetry observed by the CERN-CMS Collaboration can indeed be attributed to parton energy loss in the medium and that a good description of data is achieved when one includes a slight enhancement coming from the contribution of parton processes that modifies the asymmetry distribution of the dijet events. We compare our results to CMS data for the most central collisions and study different values for and .

    Comments:
    8 pages, 5 figures. Updated to published version with added comments and minor corrections
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1503.06889 [pdf]
    PRC(2015)·12 citations
  2. 11

    [Submitted on 24 Mar 2015] (cross-list from hep-th)

    Equilibration rates in a strongly coupled nonconformal quark-gluon plasma

    Alex Buchel🇨🇦 · Michal P. Heller🇨🇦 · Robert C. Myers🇨🇦

    We initiate the study of equilibration rates of strongly coupled quark-gluon plasmas in the absence of conformal symmetry. We primarily consider a supersymmetric mass deformation within gauge theory and use holography to compute quasinormal modes of a variety of scalar operators, as well as the energy-momentum tensor. In each case, the lowest quasinormal frequency, which provides an approximate upper bound on the thermalization time, is proportional to temperature, up to a pre-factor with only a mild temperature dependence. We find similar behaviour in other holographic plasmas, where the model contains an additional scale beyond the temperature. Hence, our study suggests that the thermalization time is generically set by the temperature, irrespective of any other scales, in strongly coupled gauge theories.

    Comments:
    6 pages, 7 figures
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1503.07114 [pdf]
    PRL(2015)·77 citations
  3. 12

    [Submitted on 24 Mar 2015] (cross-list from hep-ph)

    Bose enhancement and the ridge

    Tolga Altinoluk🇪🇸 · Néstor Armesto🇪🇸 · Guillaume Beuf🇮🇱 · Alex Kovner🇺🇸 · Michael Lublinsky🇮🇱

    We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.

    Comments:
    5 pages, 1 figure; v2: 6 pages, 1 figure, discussions enlarged and technical details added, figure changed, final version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1503.07126 [pdf]
    PLB(2015)·74 citations
  4. 13

    [Submitted on 24 Mar 2015] (cross-list from hep-th)

    Linearized nonequilibrium dynamics in nonconformal plasma

    Romuald A. Janik🇵🇱 · Grzegorz Plewa🇵🇱 · Hesam Soltanpanahi🇵🇱 · Michal Spalinski🇵🇱

    We investigate the behaviour of the lowest nonhydrodynamic modes in a class of holographic models which exhibit an equation of state closely mimicking the one determined from lattice QCD. We calculate the lowest quasinormal mode frequencies for a range of scalar self-interaction potentials and find that the damping of the quasinormal modes at the phase transition/crossover falls off by a factor of around two from conformality after factoring out standard conformal temperature dependence. The damping encoded in the imaginary part of the frequencies turns out to be correlated with the speed of sound and is basically independent of the UV details of the model. We also find that the dynamics of the nonhydrodynamic degrees of freedom remains ultralocal, even to a higher degree, as we deviate from conformality. These results indicate that the role of nonhydrodynamic degrees of freedom in the vicinity of the crossover transition may be enhanced.

    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1503.07149 [pdf]
    PRD(2015)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE