Fri·Aug 30, 2002Friday·August 30, 2002

1. 01*

   On systematic errors due to quenching in epsilon-prime over epsilon

   Maarten Golterman (San Francisco State)🇺🇸 · Elisabetta Pallante (SISSA)🇮🇹

   Recently, we pointed out that chiral transformation properties of penguin operators change in the transition from unquenched to (partially) quenched QCD. As a consequence, new operators appear in (partially) quenched QCD penguins, introducing ambiguities which should be considered a quenching artifact. Here we discuss more specifically the effects of this phenomenon on the quenched Delta I=1/2 K to pi pi amplitude, and in particular, its potential numerical effect on recent lattice estimates for epsilon-prime over epsilon.

   hep-lathep-phNucl.Phys.B Proc.Suppl.(2003)·7 citations
2. 02*

   Excited baryons from Bayesian priors and overlap fermions

   F.X. Lee🇺🇸 · S.J. Dong🇺🇸 · T. Draper🇺🇸 · I. Horvath🇺🇸 · K.F. Liu🇺🇸 · N. Mathur🇺🇸 · J.B. Zhang🇦🇺

   Using the constrained-fitting method based on Bayesian priors, we extract the masses of the two lowest states of octet and decuplet baryons with both parities. The calculation is done on quenched 16^3x28 lattices of a=0.2 fm using an improved gauge action and overlap fermions, with the pion mass as low as 180 MeV. The Roper state N(1440)1/2+ is clearly observed for the first time as the 1st-excited state of the nucleon from the standard interpolating field. Together with other baryons, our preliminary results indicate that the level-ordering of the low-lying baryon states on the lattice is largely consistent with experiment. The realization is helped by cross-overs between the excited 1/2+ and 1/2- states in the region of pion mass from 300 to 400 MeV.

   hep-lathep-phnucl-thNucl.Phys.B Proc.Suppl.(2003)·50 citations
3. 03*

   Chiral Limit of Staggered Fermions at Strong Couplings: A Loop Representation

   Shailesh Chandrasekharan🇺🇸

   The partition function of two dimensional massless staggered fermions interacting with U(N) gauge fields is rewritten in terms of loop variables in the strong coupling limit. We use this representation of the theory to devise a non-local Metropolis algorithm to calculate the chiral susceptibility. For small lattices our algorithm reproduces exact results quite accurately. Applying this algorithm to large volumes yields rather surprising results. In particular we find $m_{\pi }\ne 0$ for all $N$ and it increases with $N$. Since the talk was presented we have found reasons to believe that our algorithm breaks down for large volumes questioning the validity of our results.

   hep-latNucl.Phys.B Proc.Suppl.(2003)·3 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.