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Nuclear Theory·nucl-th

Thursday·June 21, 2018

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 05

    [Submitted on 19 Jun 2018] (cross-list from hep-ph)

    Manifestly Soft Gauge Invariant Formulation of vNRQCD

    Ira Z. Rothstein🇺🇸 · Prashant Shrivastava🇺🇸 · Iain W. Stewart🇺🇸

    Homogeneous power counting in Non-Relativistic QCD (NRQCD) implies the simultaneous existence of both soft and ultrasoft gluons. In the velocity renormalization group (vNRQCD) formalism we show that operators involving soft fields interacting with heavy potential quarks can be put in a manifestly gauge invariant form by utilizing gluon and quark building blocks which contain Wilson lines, and are analogous to those used in the soft collinear effective theory. This leads to several simplifications, in particular significantly reducing the size of the operator basis, which stream-lines matching and anomalous dimension calculations at subleading order in the velocity expansion. Also, soft ghosts no longer couple via potential like interactions to the heavy quark fields, and hence do not appear until two loops. Furthermore the the color structures that appear at each order in in the static potential are only those which should arise according to non-Abelian exponentiation. We also discuss how zero-bin subtractions clarify the role of terms in the heavy quark propagator poles carrying soft momenta. Even though the choice of the direction of the soft Wilson lines in our building blocks does not matter, there is still a limited set of consistent choices, and the predicted form of the eikonal poles does influence results at two-loops and beyond.

    Comments:
    29 pages, 7 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1806.07398 [pdf]
    NPB(2019)·13 citations
  2. 06

    [Submitted on 20 Jun 2018] (cross-list from hep-ph)

    Parton distributions from nonlocal chiral SU(3) effective theory. I. Splitting functions

    Y. Salamu🇨🇳 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸 · A. W. Thomas🇦🇺 · P. Wang🇨🇳

    We present a new formulation of pseudoscalar meson loop corrections to nucleon parton distributions within a nonlocal covariant chiral effective field theory, including contributions from SU(3) octet and decuplet baryons. The nonlocal Lagrangian, constrained by requirements of local gauge invariance and Lorentz-invariant ultraviolet regularization, generates additional interactions associated with gauge links. We use these to compute the full set of proton meson + baryon splitting functions, which in general contain on-shell and off-shell contributions, in addition to -function terms at zero momentum, along with nonlocal contributions associated with the finite size of the proton. We illustrate the shapes of the various local and nonlocal functions numerically using a simple example of a dipole regulator.

    Comments:
    43 pages, 6 figures, version to appear in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1806.07551 [pdf]
    PRD(2019)·30 citations
  3. 07

    [Submitted on 20 Jun 2018] (cross-list from hep-ph)

    Shear viscosity of ultrarelativistic Boson systems in the presence of a Bose-Einstein condensate

    Zhengyu Chen🇨🇳 · Carsten Greiner🇩🇪 · Zhe Xu🇨🇳 · Pengfei Zhuang🇨🇳

    We calculate for the first time the shear viscosity of ultrarelativistic Boson systems in the presence of a Bose-Einstein condensate (BEC). Two different methods are used. One is the Grad's method of moments and another is the Green-Kubo relation within a kinetic transport approach. In this work we consider a Boson system with isotropic elastic collisions and a gluon system with elastic scatterings described by perturbation QCD (pQCD). The results show that the presence of a BEC lowers the shear viscosity. This effect becomes stronger for the increasing proportion of the BEC in the Boson system and is insensitive to the detail of interactions.

    Comments:
    11 pages, 3 figures, matches published version
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1806.07594 [pdf]
    PRC(2019)·6 citations
  4. 08

    [Submitted on 20 Jun 2018] (cross-list from hep-ph)

    Proton shape fluctuations and its relation to DIS

    Heikki Mäntysaari🇫🇮

    We review the recent progress in extracting the proton fluctuating substructure by studying exclusive processes at HERA, and the applications of these developments in the interpretation of the LHC heavy ion data. The possibilities to extract the proton geometry directly from the LHC high-multiplicity proton-nucleus and proton-proton collision data is also discussed.

    Comments:
    10 pages, 8 figures. Invited talk at the XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects, April 2018
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1806.07612 [pdf]
    PoS(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE