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Nuclear Theory·nucl-th

Thursday·November 19, 2015

11 papers—8 primary·3 cross-listed

All11Primary8Cross-lists3
  1. 09

    [Submitted on 18 Nov 2015] (cross-list from hep-ph)

    Pion photo- and electroproduction and the chiral MAID interface

    M. Hilt🇩🇪 · B. C. Lehnhart🇩🇪 · S. Scherer🇩🇪 · L. Tiator🇩🇪

    We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order . The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/). We explain how our program works and how it can be used for further analysis.

    Comments:
    20 pages, 12 figures, invited plenary talk given by S. Scherer at the 8th International Workshop on Chiral Dynamics, CD2015, 29 June 2015 - 03 July 2015, Pisa, Italy, draws on arXiv:1510.04602 [nucl-th]
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1511.05679 [pdf]
    PoS(2016)·0 citations
  2. 10

    [Submitted on 18 Nov 2015] (cross-list from hep-ph)

    SU(2N_F) hidden symmetry of QCD

    L. Ya. Glozman🇦🇹

    Recently a global SU(4) \supset SU(2)_L \times SU(2)_R \times U(1)_A symmetry of the confining Coulombic part of the QCD Hamiltonian has been discovered with N_F=2. This global symmetry includes both independent rotations of the left- and right-handed quarks in the isospin space as well as the chiralspin rotations that mix the left- and right-handed components of the quark fields. It has been suggested by lattice simulations, however, that a symmetry of mesons in the light quark sector upon the quasi-zero mode truncation from the quark propagators is actually higher than SU(4), because the states from a singlet and a 15-plet irreducible representations of SU(4) are also degenerate. Here we demonstrate that classically QCD, ignoring irrelevant exact zero mode contributions, has a SU(2N_F) symmetry. If effects of dynamical chiral symmetry breaking and of anomaly are encoded in the same near-zero modes, then truncation of these modes should restore a classical SU(2N_F) symmetry. Then we show in a Lorentz- and gauge-invariant manner emergence of a bilocal SU(4) \times SU(4) symmetry in mesons that contains a global SU(4) as a subgroup upon truncation of the quasi-zero modes. We also demonstrate that the confining Coulombic part of the QCD Hamiltonian has this bilocal symmetry. It explains naturally a degeneracy of different irreducible representations of SU(4) observed in lattice simulations.

    Comments:
    7 pp. Further clarifications and references have been added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1511.05857 [pdf]
    14 citations
  3. 11

    [Submitted on 18 Nov 2015] (cross-list from hep-lat)

    Lattice calculation of the HVP contribution to the anomalous magnetic moment of muon

    Bipasha Chakraborty🇬🇧 · Christine Davies🇬🇧 · Pedro Gonçalves de Oliveira🇬🇧 · Jonna Koponen🇬🇧 · G. Peter Lepage🇺🇸

    We report our (HPQCD) progress on the calculation of the Hadronic Vacuum Polarisation contribution to the anomalous magnetic moment of muon. In this article we discuss the calculations for the light (up/down) quark connected contribution using our method described in Phys.Rev. D89(2014) 11, 114501 and give an estimate for the disconnected contribution. Our calculation has been carried out on MILC Collaboration's HISQ ensembles at multiple values of the lattice spacing, multiple volumes and multiple light sea quark masses (including physical pion mass configurations).

    Comments:
    7 pages, 5 figures, The 33rd International Symposium on Lattice Field Theory
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1511.05870 [pdf]
    PoS(2015)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE