Tue·Aug 30, 2005Tuesday·August 30, 2005

1. 01*

   Finite Size Effect in Excited Baryon Spectroscopy

   Kiyoshi Sasaki (1)🇯🇵 · Shoichi Sasaki (2 and 3) ((1)Univ. of Tsukuba, (2) Univ. of Tokyo, (3) RIKEN BNL)🇯🇵

   We investigate the finite size effect on masses of excited baryons in quenched lattice QCD simulation. For this purpose, we perform numerical simulations at three different lattice sizes, La\simeq 1.6, 2.2 and 3.2 fm. The gauge configurations are generated with the single plaquette gauge action at \beta=6/g^2=6.2, and the quark propagator are computed with the Wilson fermion action. To access to two parity states of the nucleon and four different spin-parity states of the \Delta baryon, the appropriate spin/parity projection are carried out. We find that the spatial lattice size is required to be as large as 3 fm to remove the finite size effect on excited baryons even in the heavy quark region (M_\pi/M_\rho\simeq 0.82, 0.87), where that on the nucleon is negligible. On our largest lattice (La\simeq 3.2 fm), all mass spectra of the J^P=1/2^\pm nucleons and the J^P=1/2^\pm, 3/2^\pm \Delta baryons are roughly consistent with experimental values after naive chiral extrapolation.

   hep-latPoS(2006)·6 citations
2. 02*

   A combined study of the gluon and ghost condensates <A^2> and <epsilon^{abc} cbar^b c^c> in Euclidean SU(2) Yang-Mills theory in the Landau gauge

   M. A. L. Capri🇧🇷 · D. Dudal🇧🇪 · J. A. Gracey🇬🇧 · V. E. R. Lemes🇧🇷 · R. F. Sobreiro🇧🇷 · S. P. Sorella🇧🇷 · H. Verschelde🇧🇪

   The ghost condensate <epsilon^{abc} cbar^b c^c> is considered together with the gluon condensate <A^2> in SU(2) Euclidean Yang-Mills theories quantized in the Landau gauge. The vacuum polarization ceases to be transverse due to the nonvanishing condensate <epsilon^{abc} cbar^b c^c>. The gluon propagator itself remains transverse. By polarization effects, this ghost condensate induces then a splitting in the gluon mass parameter, which is dynamically generated through <A^2>. The obtained effective masses are real when <A^2> is included in the analysis. In the absence of <A^2>, the already known result that the ghost condensate induces effective tachyonic masses is recovered. At the one-loop level, we find that the effective diagonal mass becomes smaller than the off-diagonal one. This might serve as an indication for some kind of Abelian dominance in the Landau gauge, similar to what happens in the maximal Abelian gauge.

   ↳ hep-thhep-latPRD(2006)·14 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.