Tue·Sep 4, 2007Tuesday·September 4, 2007

1. 01*

   Lattice QCD determination of patterns of excited baryon states

   Subhasish Basak🇺🇸 · R. G. Edwards🇺🇸 · G. T. Fleming🇺🇸 · K. J. Juge🇺🇸 · A. Lichtl🇺🇸 · C. Morningstar🇺🇸 · D. G. Richards🇺🇸 · I. Sato🇺🇸 · S. J. Wallace🇺🇸

   Energies for excited isospin I=1/2 and I=3/2 states that include the nucleon and Delta families of baryons are computed using quenched, anisotropic lattices. Baryon interpolating field operators that are used include nonlocal operators that provide G_2 irreducible representations of the octahedral group. The decomposition of spin 5/2 or higher spin states is realized for the first time in a lattice QCD calculation. We observe patterns of degenerate energies in the irreducible representations of the octahedral group that correspond to the subduction of the continuum spin 5/2 or higher. The overall pattern of low-lying excited states corresponds well to the pattern of physical states subduced to the irreducible representations of the octahedral group.

   hep-latPRD(2007)·102 citations
2. 02*

   How far can you go ? Surprises and pitfalls in three-flavour chiral extrapolations

   S. Descotes-Genon (LPT Orsay)🇫🇷

   The presence of strange sea quark pairs may have a significant impact of the pattern of chiral symmetry breaking : in particular large differences can occur between the chiral limits of two and three massless flavours (i.e., whether $m_s$ is kept at its physical value or sent to zero). We recall some indications of such a scenario in QCD, in relation with the peculiar dynamics of the scalar sector. We explain how this could affect the convergence of three-flavour chiral series, commonly used to extrapolate the results of lattice simulations. Finally, we indicate how lattice simulations with three dynamical flavours could unveil such an effect through the quark-mass dependence of light meson masses and decay constants.

   hep-latPoS(2007)·5 citations
3. 03*

   On the possibility of P-violation at finite baryon-number densities

   A. A. Andrianov🇪🇸 · D. Espriu🇪🇸

   We show how the introduction of a finite baryon density may trigger spontaneous parity violation in the hadronic phase of QCD. Since this involves strong interaction physics in an intermediate energy range we approximate QCD by a \sigma model that retains the two lowest scalar and pseudoscalar multiplets. We propose a novel mechanism based on interplay between lightest and heavy meson states which cannot be realized solely in the Goldstone boson (pion) sector and thereby is unrelated to the one advocated by Migdal some time ago. Our approach is relevant for dense matter in an intermediate regime of few nuclear densities where quark percolation does not yet play a significant role.

   ↳ hep-phastro-phhep-lathep-th+1PLB(2008)·51 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.