Hong Liu

Publications (4)0 Total impact

• Article: Momentum Broadening in Weakly Coupled Quark-Gluon Plasma (with a view to finding the quasiparticles within liquid quark-gluon plasma)

  Francesco D'Eramo, Mindaugas Lekaveckas, Hong Liu, Krishna Rajagopal
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  ABSTRACT: We calculate P(k_\perp), the probability distribution for an energetic parton that propagates for a distance L through a medium without radiating to pick up transverse momentum k_\perp, for a medium consisting of weakly coupled quark-gluon plasma. We use full or HTL self-energies in appropriate regimes, resumming each in order to find the leading large-L behavior. The jet quenching parameter \hat q is the second moment of P(k_\perp), and we compare our results to other determinations of this quantity in the literature, although we emphasize the importance of looking at P(k_\perp) in its entirety. We compare our results for P(k_\perp) in weakly coupled quark-gluon plasma to expectations from holographic calculations that assume a plasma that is strongly coupled at all length scales. We find that the shape of P(k_\perp) at modest k_\perp may not be very different in weakly coupled and strongly coupled plasmas, but we find that P(k_\perp) must be parametrically larger in a weakly coupled plasma than in a strongly coupled plasma at large enough k_\perp. This means that by looking for rare (but not exponentially rare) large-angle deflections of the jet resulting from a parton produced initially back-to-back with a hard photon, experimentalists can find the weakly coupled short-distance quark and gluon quasiparticles within the strongly coupled liquid quark-gluon plasma produced in heavy ion collisions, much as Rutherford found nuclei within atoms or Friedman, Kendall and Taylor found quarks within nucleons.
  11/2012;
• Source

  Available from: ArXiv

  Article: Momentum Broadening in Weakly Coupled Quark-Gluon Plasma

  Francesco D'Eramo, Christopher Lee, Mindaugas Lekaveckas, Hong Liu, Krishna Rajagopal
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  ABSTRACT: We calculate the probability distribution P(k_\perp) for the momentum perpendicular to its original direction of motion that an energetic quark or gluon picks up as it propagates through weakly coupled quark-gluon plasma in thermal equilibrium.
  10/2011;
• Source

  Available from: ArXiv

  Article: Jet Quenching Parameter via Soft Collinear Effective Theory (SCET)

  Francesco D'Eramo, Hong Liu, Krishna Rajagopal
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  ABSTRACT: We analyze the transverse momentum broadening in the absence of radiation of an energetic parton propagating through quark-gluon plasma via Soft Collinear Effective Theory (SCET). We show that the probability for picking up transverse momentum k_\perp is given by the Fourier transform of the expectation value of two transversely separated light-like path-ordered Wilson lines. The subtleties about the ordering of operators do not change the \hat q value for the strongly coupled plasma of N=4 SYM theory.
  10/2010;
• Source

  Available from: ArXiv

  Article: Transverse Momentum Broadening and the Jet Quenching Parameter, Redux

  Francesco D'Eramo, Hong Liu, Krishna Rajagopal
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  ABSTRACT: We use Soft Collinear Effective Theory (SCET) to analyze the transverse momentum broadening, or diffusion in transverse momentum space, of an energetic parton propagating through quark-gluon plasma. Since we neglect the radiation of gluons from the energetic parton, we can only discuss momentum broadening, not parton energy loss. The interaction responsible for momentum broadening in the absence of radiation is that between the energetic (collinear) parton and the Glauber modes of the gluon fields in the medium. We derive the effective Lagrangian for this interaction, and we show that the probability for picking up transverse momentum k_\perp is given by the Fourier transform of the expectation value of two transversely separated light-like path-ordered Wilson lines. This yields a field theoretical definition of the jet quenching parameter \hat q, and shows that this can be interpreted as a diffusion constant. We close by revisiting the calculation of \hat q for the strongly coupled plasma of N=4 SYM theory, showing that previous calculations need some modifications that make them more straightforward and do not change the result.
  06/2010;