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Nuclear Theory·nucl-th

Friday·June 5, 2015

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    Symmetry energy in cold dense matter

    Kie Sang Jeong🇰🇷 · Su Houng Lee🇰🇷

    We calculate the symmetry energy in cold dense matter both in the normal quark phase and in the 2-color superconductor (2SC) phase. For the normal phase, the thermodynamic potential is calculated by using hard dense loop (HDL) resummation to leading order, where the dominant contribution comes from the longitudinal gluon rest mass. The effect of gluonic interaction to the symmetry energy, obtained from the thermodynamic potential, was found to be small. In the 2SC phase, the non-perturbative BCS paring gives enhanced symmetry energy as the gapped states are forced to be in the common Fermi sea reducing the number of available quarks that can contribute to the asymmetry. We used high density effective field theory to estimate the contribution of gluon interaction to the symmetry energy. Among the gluon rest masses in 2SC phase, only the Meissner mass has iso-spin dependence although the magnitude is much smaller than the Debye mass. As the iso-spin dependence of gluon rest masses is even smaller than the case in the normal phase, we expect that the contribution of gluonic interaction to the symmetry energy in the 2SC phase will be minimal. The different value of symmetry energy in each phase will lead to different prediction for the particle yields in heavy ion collision experiment.

    nucl-thhep-phNPA(2016)·9 citations
  2. 02

    Back-to-back correlations of boson-antiboson pairs for anisotropic expanding sources

    Yong Zhang🇨🇳 · Jing Yang🇨🇳 · Wei-Ning Zhang🇨🇳

    In the hot and dense hadronic sources formed in high energy heavy ion collisions, the particle interactions in medium might lead to a measurable back-to-back correlation (BBC) of boson-antiboson pairs. We calculate the BBC functions of and for anisotropic expanding sources. The dependences of the BBC on the particle momentum and source expanding velocity are investigated. The results indicate that the BBC functions increase with the magnitude of particle momentum and exhibit an obvious dependence on the direction of the momentum for the anisotropic sources. As the source expanding velocity decreases, the BBC function decreases when the particle momentum is approximately perpendicular to the source velocity, and the BBC function increases when the particle momentum is approximately parallel to the source velocity.

    nucl-thIJMPE(2015)·3 citations
  3. 03

    The anomalous transport of axial charge: topological vs non-topological fluctuations

    Ioannis Iatrakis🇺🇸 · Shu Lin🇺🇸 · Yi Yin🇺🇸

    Axial charge imbalance is an essential ingredient in novel effects associated with chiral anomaly such as chiral magnetic effects (CME). In a non-Abelian plasma with chiral fermions, local axial charge can be generated a) by topological fluctuations which would create domains with non-zero winding number b) by conventional non-topological thermal fluctuations. We provide a holographic evaluations of medium's response to dynamically generated axial charge density in hydrodynamic limit and examine if medium's response depends on the microscopic origins of axial charge imbalance. We show a local domain with non-zero winding number would induce a non-dissipative axial current due to chiral anomaly. We illustrate holographically that a local axial charge imbalance would be damped out with the damping rate related to Chern-Simon diffusive constant. By computing chiral magnetic current in the presence of dynamically generated axial charge density, we found that the ratio of CME current over the axial charge density is independent of the origin of axial charge imbalance in low frequency and momentum limit. Finally, a stochastic hydrodynamic equation of the axial charge is formulated by including both types of fluctuations.

    ↳ hep-thhep-phnucl-thJHEP(2015)·27 citations
  4. 04

    Dispersion relation for hadronic light-by-light scattering: theoretical foundations

    Gilberto Colangelo🇨🇭 · Martin Hoferichter🇩🇪 · Massimiliano Procura🇦🇹 · Peter Stoffer🇩🇪

    In this paper we make a further step towards a dispersive description of the hadronic light-by-light (HLbL) tensor, which should ultimately lead to a data-driven evaluation of its contribution to . We first provide a Lorentz decomposition of the HLbL tensor performed according to the general recipe by Bardeen, Tung, and Tarrach, generalizing and extending our previous approach, which was constructed in terms of a basis of helicity amplitudes. Such a tensor decomposition has several advantages: the role of gauge invariance and crossing symmetry becomes fully transparent; the scalar coefficient functions are free of kinematic singularities and zeros, and thus fulfill a Mandelstam double-dispersive representation; and the explicit relation for the HLbL contribution to in terms of the coefficient functions simplifies substantially. We demonstrate explicitly that the dispersive approach defines both the pion-pole and the pion-loop contribution unambiguously and in a model-independent way. The pion loop, dispersively defined as pion-box topology, is proven to coincide exactly with the one-loop scalar QED amplitude, multiplied by the appropriate pion vector form factors.

    ↳ hep-phhep-exhep-latnucl-thJHEP(2015)·328 citations

Affiliations

first authorsco-authorsvia INSPIRE