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Nuclear Theory·nucl-th

Tuesday·April 25, 2017

14 papers—8 primary·6 cross-listed

All14Primary8Cross-lists6
  1. 09

    [Submitted on 22 Apr 2017] (cross-list from hep-lat)

    Connected and Disconnected Contractions in Pion-Pion Scattering

    Neramballi Ripunjay Acharya🇨🇳 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Chien-Yeah Seng🇨🇳

    We show that the interplay of chiral effective field theory and lattice QCD can be used in the evaluation of so-called disconnected diagrams, which appear in the study of the isoscalar and isovector channels of pion-pion scattering and have long been a major challenge for the lattice community. By means of partially-quenched chiral perturbation theory, we distinguish and analyze the effects from different types of contraction diagrams to the pion-pion scattering amplitude, including its scattering lengths and the energy-dependence of its imaginary part. Our results may be used to test the current degree of accuracy of lattice calculation in the handling of disconnected diagrams, as well as to set criteria for the future improvement of relevant lattice computational techniques that may play a critical role in the study of other interesting QCD matrix elements.

    Comments:
    18 pages, 3 figures, 3 tables
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1704.06754 [pdf]
    NPB(2017)·15 citations
  2. 10

    [Submitted on 23 Apr 2017] (cross-list from hep-ph)

    Quarkonium as relativistic bound state on the light front

    Yang Li🇺🇸 · Pieter Maris🇺🇸 · James P. Vary🇺🇸

    We study charmonium and bottomonium as relativistic bound states in a light-front quantized Hamiltonian formalism. The effective Hamiltonian is based on light-front holography. We use a recently proposed longitudinal confinement to complete the soft-wall holographic potential for the heavy flavors. The spin structure is generated from the one-gluon exchange interaction with a running coupling. The adoption of asymptotic freedom improves the spectroscopy compared with previous light-front results. Within this model, we compute the mass spectroscopy, decay constants and the r.m.s. radii. We also present a detailed study of the obtained light-front wave functions and use the wave functions to compute the light-cone distributions, specifically the distribution amplitudes and parton distribution functions. Overall, our model provides a reasonable description of the heavy quarkonia.

    Comments:
    28 pages, 17 figures, 5 tables. Supplemental Materials are provided in the source file under "Other formats" (see also "Ancillary files")
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1704.06968 [pdf]
    PRD(2017)·147 citations
  3. 11

    [Submitted on 24 Apr 2017] (cross-list from nucl-ex)

    Probing non-linearity of higher order anisotropic flow in Pb--Pb collisions

    You Zhou (on behalf of the ALICE Collaboration)🇩🇰

    The second and the third order anisotropic flow, and , are determined by the corresponding initial spatial anisotropy coefficients, and , in the initial density distribution. On the contrary, the higher order anisotropic flow (), in addition to their dependence on the same order initial anisotropy coefficient , have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this contribution, we present the investigations on linear and non-linear modes in higher order anisotropic flow (, and ) in Pb--Pb collisions at 2.76 TeV using the ALICE detector at the Large Hadron Collider (LHC). A significant contribution from a non-linear mode is observed. A new observable, the non-linear response coefficient, is measured as well. The comparison to theoretical calculations provides crucial information on dynamic of the created system especially at the freeze-out conditions, which are poorly known from previous flow measurements.

    Comments:
    4 pages, 3 figures, XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2017), Chicago, US
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1704.07070 [pdf]
    NPA(2017)·1 citation
  4. 12

    [Submitted on 24 Apr 2017] (cross-list from hep-ph)

    Polyakov loop correlator in perturbation theory

    Matthias Berwein🇯🇵 · Nora Brambilla🇩🇪 · Peter Petreczky🇺🇸 · Antonio Vairo🇩🇪

    We study the Polyakov loop correlator in the weak coupling expansion and show how the perturbative series re-exponentiates into singlet and adjoint contributions. We calculate the order correction to the Polyakov loop correlator in the short distance limit. We show how the singlet and adjoint free energies arising from the re-exponentiation formula of the Polyakov loop correlator are related to the gauge invariant singlet and octet free energies that can be defined in pNRQCD, namely we find that the two definitions agree at leading order in the multipole expansion, but differ at first order in the quark-antiquark distance.

    Comments:
    58 pages, 2 figures; v2 journal version; v3 misprints corrected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1704.07266 [pdf]
    PRD(2017)·22 citations
  5. 13

    [Submitted on 24 Apr 2017] (cross-list from hep-ph)

    Spin partners of the and revisited

    V. Baru🇷🇺 · E. Epelbaum🇩🇪 · A. A. Filin🇩🇪 · C. Hanhart🇩🇪 · A. V. Nefediev🇷🇺

    We study the implications of the heavy-quark spin symmetry for the possible spin partners of the exotic states and in the spectrum of bottomonium. We formulate and solve numerically the coupled-channel equations for the states that allow for a dynamical generation of these states as hadronic molecules. The force includes short-range contact terms and the one-pion exchange potential, both treated fully nonperturbatively. The strength of the potential at leading order is fixed completely by the pole positions of the states such that the mass and the most prominent contributions to the width of the isovector heavy-quark spin partner states with the quantum numbers () come out as predictions. Since the accuracy of the present experimental data does not allow one to fix the pole positions of the 's reliably enough, we also study the pole trajectories of their spin partner states as functions of the binding energies. It is shown that, once the heavy-quark spin symmetry is broken by means of the physical and masses, especially the pion tensor force has a significant impact on the location of the partner states clearly demonstrating the need of a coupled-channel treatment of pion dynamics to understand the spin multiplet pattern of hadronic molecules.

    Comments:
    21 pages, 5 figures, 1 table
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1704.07332 [pdf]
    JHEP(2017)·52 citations
  6. 14

    [Submitted on 24 Apr 2017] (cross-list from hep-lat)

    Taming the Signal-to-Noise Problem in Lattice QCD by Phase Reweighting

    Michael L. Wagman🇺🇸 · Martin J. Savage🇺🇸

    Path integrals describing quantum many-body systems can be calculated with Monte Carlo sampling techniques, but average quantities are often subject to signal-to-noise ratios that degrade exponentially with time. A phase-reweighting technique inspired by recent observations of random walk statistics in correlation functions is proposed that allows energy levels to be extracted from late-time correlation functions with time-independent signal-to-noise ratios. Phase reweighting effectively includes dynamical refinement of source magnitudes but introduces a bias associated with the phase. This bias can be removed by performing an extrapolation, but at the expense of re-introducing a signal-to-noise problem. Lattice Quantum Chromodynamics calculations of the and nucleon masses and of the binding energy show consistency between standard results obtained using earlier-time correlation functions and phase-reweighted results using late-time correlation functions inaccessible to standard statistical analysis methods.

    Comments:
    7 pages, 6 figures. Higher statistics, minor revisions
    Subjects:
    High Energy Physics — Lattice (hep-lat); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1704.07356 [pdf]
    20 citations

Affiliations

first authorsco-authorsvia INSPIRE