Fri·Oct 19, 2007Friday·October 19, 2007

1. 01*

   Kaon Weak Matrix Elements in 2+1 flavor DWF QCD

   Shu Li · Robert D. Mawhinney for RBC · UKQCD Collaborations

   $K\to \pi$ and $K\to 0$ weak matrix elements of $\Delta S=1$ operators have been measured in 2+1 flavor domain wall fermion (DWF) QCD on (3 fm)${}^3$ lattices with $a^{-1}=1.73(3)$ GeV. As is well known, using these matrix elements and chiral perturbation theory allows a determination of the $K\to \pi \pi$ matrix elements that enter in the quantitative value for the $\Delta I=1/2$ rule and ${ϵ}^{\prime }/ϵ$. Two light dynamical sea quark masses have been used, along with six valence quark masses, with the lightest valence quark mass $\approx 1/10$ the physical strange quark mass. We report our results for lattice matrix elements in the $SU(3{)}_L\times SU(3{)}_R$ (27,1), (8,1), and (8,8) representations, paying particular attention to the statistical errors achieved after measurements on 75 configurations. We also report on our calculation of the non-perturbative renormalization coefficients for these $\Delta S=1$ weak operators, using the Rome-Southampton method.

   hep-latPoS(2007)·1 citation
2. 02*

   Light hadron spectrum with 2+1 flavor dynamical $O(a)$-improved Wilson quarks

   PACS-CS Collaboration:N. Ukita🇯🇵 · S. Aoki🇯🇵 · N. Ishii🇯🇵 · K.-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · T. Izubuchi🇺🇸 · D. Kadoh🇯🇵 · K. Kanaya🇯🇵 · Y. Kuramashi🇯🇵 · Y. Namekawa🇯🇵 · M. Okawa🇯🇵 · K. Sasaki🇯🇵 and 3 other authors

   We present preliminary results for the light harden spectrum in $N_f=2+1$ lattice QCD obtained with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action. Simulations are carried out at $\beta =1.90$ on a $32^3\times 64$ lattice using the PACS-CS computer. We employ Lüscher's domain-decomposed HMC algorithm to reduce the up-down quark masses toward the physical value. The pseudoscalar meson masses range from 730 MeV down to 210 MeV. We compare the light harden spectrum extrapolated to the physical point with the experimental values.

   hep-latPoS(2007)·18 citations
3. 03*

   Application of chiral perturbation theory to 2+1 flavor lattice QCD with O(a)-improved Wilson quarks

   PACS-CS Collaboration: D. Kadoh🇯🇵 · S. Aoki🇯🇵 · N. Ishii🇯🇵 · K.I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · T. Izubuchi🇺🇸 · K. Kanaya🇯🇵 · Y. Kuramashi🇯🇵 · Y. Namekawa🇯🇵 · M. Okawa🇯🇵 · K. Sasaki🇯🇵 · Y. Taniguchi🇯🇵 and 3 other authors

   We apply chiral perturbation theory to the pseudoscalar meson mass and decay constant data obtained in the PACS-CS Project toward 2+1 flavor lattice QCD simulations with the O(a)-improved Wilson quarks. We examine the existence of chiral logarithms in the quark mass range from m_{ud}=47 MeV down to 6 MeV on a (2.8 fm)^3 box with the lattice spacing a=0.09 fm. Several low energy constants are determined. We also discuss the magnitude of finite size effects based on chiral perturbation theory.

   hep-latPoS(2007)·16 citations
4. 04*

   Meson correlators in the epsilon-regime of two-flavor lattice QCD

   JLQCD collaboration : H. Fukaya🇯🇵 · S. Aoki🇯🇵 · S. Hashimoto🇯🇵 · T. Kaneko🇯🇵 · H. Matsufuru🇯🇵 · J. Noaki🇯🇵 · K. Ogawa🇹🇼 · T. Onogi🇯🇵 · N. Yamada🇯🇵

   We calculate the meson correlators in the $ϵ$-regime of two-flavor QCD. On a $16^3\times 32$ lattice with $a\sim 0.11$ fm, the lattice simulations are performed with the dynamical overlap fermions. We reduce the sea quark mass down to $\sim$ 3 MeV and the valence quark masses are taken in the range 1-4 MeV. The meson correlators in various channels are compared with the predictions of (partially quenched) chiral perturbation theory (ChPT). Including the NLO order of the $ϵ$-expansion, we extract the leading-order low energy constants of ChPT, the pion decay constant $F$ and the chiral condensate $\Sigma$, as $F=87.3(5.5)$ MeV and ${\Sigma }^{\overline{\mathrm{MS}}}=[237.8(4.0)MeV{]}^3$.

   hep-latPoS(2007)·7 citations
5. 05*

   Use and misuse of ChPT in the heavy-light systems

   Damir Becirevic🇫🇷 · Svjetlana Fajfer🇸🇮 · Jernej Kamenik🇮🇹

   We discuss the range of validity of ChPT when applied to the systems of heavy-light mesons. Having in mind the recent experimental evidence according to which the heavy-light scalar and axial states are closer to the ground states than anticipated, we revisited the prediction for the chiral behavior of the B-Bbar mixing amplitude and examined the impact of nearness of the positive parity states. We conclude that the standard ChPT expressions with Nf=3 light flavours are not useful in guiding the extrapolation of hadronic quantities computed on the lattice. Instead those derived in HMChPT with Nf=2, i.e., including only the pion loops, are still adequate as long as they are applied to the pions lighter than 350 MeV, or the quarks lighter than a third of the physical strange quark mass.

   hep-lathep-phPoS(2007)·12 citations
6. 06*

   K-string tensions at finite temperature and integrable models

   Michele Caselle🇮🇹 · Pietro Giudice🇮🇹 · Ferdinando Gliozzi🇮🇹 · Paolo Grinza🇮🇹 · Stefano Lottini🇮🇹

   It has recently been pointed out that simple scaling properties of Polyakov correlation functions of gauge systems in the confining phase suggest that the ratios of k-string tensions in the low temperature region is constant up to terms of order T^3. Here we argue that, at least in a three-dimensional Z_4 gauge model, the above ratios are constant in the whole confining phase. This result is obtained by combining numerical experiments with known exact results on the mass spectrum of an integrable two-dimensional spin model describing the infrared behaviour of the gauge system near the deconfining transition.

   hep-lathep-thJHEP(2007)·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.