PaperPanorama
FAQ

Nuclear Theory·nucl-th

Tuesday·July 31, 2018

10 papers—4 primary·6 cross-listed

All10Primary4Cross-lists6
  1. 05

    [Submitted on 27 Jul 2018] (cross-list from hep-ph)

    Coarse graining scattering

    Jacobo Ruiz de Elvira🇨🇭 · Enrique Ruiz Arriola🇪🇸

    We carry out an analysis of scattering in the , and channels in configuration space up to a maximal center-of-mass energy GeV. We separate the interaction into two regions marked by an elementarity radius of the system; namely, a long distance region above which pions can be assumed to interact as elementary particles and a short distance region where many physical effects cannot be disentangled. The long distance interaction is described by chiral dynamics, where a two-pion-exchange potential is identified, computed and compared to lattice calculations. The short distance piece corresponds to a coarse grained description exemplified by a superposition of delta-shell potentials sampling the interaction with the minimal wavelength. We show how the so constructed non-perturbative scattering amplitude complies with the proper analytic structure, allowing for an explicit N/D type decomposition in terms of the corresponding Jost functions and fulfilling dispersion relations without subtractions. We also address renormalization issues in coordinate space and investigate the role of crossing when fitting the scattering amplitudes above and below threshold to Roy-equation results. At higher energies, we show how inelasticities can be described by one single complex and energy dependent parameter. A successful description of the data can be achieved with a minimal number of fitting parameters, suggesting that coarse graining is a viable approach to analyze hadronic processes.

    Comments:
    27 pages, 13 Figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.10837 [pdf]
    EPJC(2018)·14 citations
  2. 06

    [Submitted on 28 Jul 2018] (cross-list from hep-ph)

    Generalized linear sigma model with two glueballs

    Amir H. Fariborz🇺🇸 · Renata Jora🇷🇴

    We present a generalized linear sigma model that includes both scalar and pseudoscalar glueballs in addition to a quark-antiquark as well as a four-quark chiral nonet. Utilizing the axial and trace anomalies of QCD (at the effective mesonic level), we aim to develope the most general structure of the Lagrangian which can be used to study the interaction of quarkonia with glueballs. We then study the effect of scalar glueball on the vacuum of the model by considering a decoupling limit in which the glueball fields are decoupled from quarkonia. This determines the properties of the pure scalar glueball and builds a practical foundation for determining the model parameters when the interactions are turned on.

    Comments:
    24 pages, version accepted for publication in Phys. Rev. D
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.10927 [pdf]
    PRD(2018)·11 citations
  3. 07

    [Submitted on 28 Jul 2018] (cross-list from hep-ph)

    Comment on scalar glueball mass

    Amir H. Fariborz🇺🇸 · Renata Jora🇷🇴

    We study the interaction of scalar glueball with quark-antiquark and four-quark spinless meson fields within the framework of a generalized linear sigma model in which the trace anomaly of QCD is exactly realized. To determine the pure scalar glueball mass (), we consider the decoupling limit in which the scalar glueball decouples from the meson fields. We find the exact relationship where is the vacuum expectation value of the scalar glueball field independent of the properties of the framework used.

    Comments:
    4 pages, 1 figure
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    1807.10928 [pdf]
    PLB(2019)·9 citations
  4. 08

    [Submitted on 29 Jul 2018] (cross-list from hep-th)

    Spin tensor and its role in non-equilibrium thermodynamics

    F. Becattini🇮🇹 · W. Florkowski🇵🇱 · E. Speranza🇩🇪

    It is shown that the description of a relativistic fluid at local thermodynamic equilibrium depends on the particular quantum stress-energy tensor operator chosen, e.g., the canonical or symmetrized Belinfante stress-energy tensor. We argue that the Belinfante tensor is not appropriate to describe a relativistic fluid whose macroscopic polarization relaxes slowly to thermodynamic equilibrium and that a spin tensor, like the canonical spin tensor, is required. As a consequence, the description of a polarized relativistic fluid involves an extension of relativistic hydrodynamics including a new antisymmetric rank-two tensor as a dynamical field. We show that the canonical and Belinfante tensors lead to different predictions for measurable quantities such as spectrum and polarization of particles produced in relativistic heavy-ion collisions.

    Comments:
    9 pages, 1 figure. Final version to appear in Phys. Lett. B
    Subjects:
    High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    1807.10994 [pdf]
    PLB(2019)·171 citations
  5. 09

    [Submitted on 30 Jul 2018] (cross-list from hep-ph)

    Adding vacuum branching to jet evolution in a dense medium

    P. Caucal🇫🇷 · E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · G. Soyez🇫🇷

    We study the fragmentation of a jet propagating in a dense quark-gluon plasma. We show that the "vacuum-like" emissions triggered by the parton virtualities can be factorized from the medium-induced radiation responsible for the energy loss within a controlled, "double-logarithmic", approximation in perturbative QCD. We show that the collisions with the plasma constituents modify the vacuum-like parton shower already at leading twist, in two ways: the radiation phase-space is reduced and the first emission outside the medium can violate angular ordering. We compute the jet fragmentation function and find results in qualitative agreement with measurements at the LHC.

    Comments:
    4 pages, 2 figures, to appear in the Proceedings of Quark Matter 2018 (14-19 May 2018. Venice, Italy)
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1807.11229 [pdf]
    NPA(2019)·0 citations
  6. 10

    [Submitted on 30 Jul 2018] (cross-list from hep-ph)

    Angular distributions in electroweak pion production off nucleons: odd parity hadron terms, strong relative phases and model dependence

    J.E. Sobczyk🇪🇸 · E. Hernández🇪🇸 · S.X. Nakamura🇧🇷 · J. Nieves🇪🇸 · T. Sato🇯🇵

    The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the charged-current and neutral-current neutrino and antineutrino pion production off nucleons, paying a special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and time-reversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three, state of the art, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parity violating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pion-nucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations.

    Comments:
    41 latex pages, 26 figures. Figure 4b corrected. Misprints corrected
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1807.11281 [pdf]
    PRD(2018)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE