Tue·Oct 11, 2005Tuesday·October 11, 2005

1. 01*

   OPE Analysis of QCD Potential and Determination of Lambda_MSbar

   Y. Sumino🇯🇵

   We analyze the static QCD potential in the distance region 0.1 fm < r < 1 fm. We combine most recent lattice computations and perturbative computations of the potential, in the framework of operator-product expansion (OPE). We determine simultaneously the non-perturbative contribution to the potential, delta E_US(r), and the relation between the lattice scale (Sommer scale) and Lambda_MSbar in the quenched approximation. We find that (1) large part of the short-distance linear potential belongs to the perturbative Wilson coefficient, (2) delta E_US(r) =0 is disfavored, and (3) r_0 Lambda_MSbar^(3-loop)=0.574 +- 0.042 . It provides a new method for precise determination of r_0 Lambda_MSbar.

   hep-lathep-phhep-thPoS(2006)·0 citations
2. 02*

   $B\to D^{\ast }l\nu$ with staggered chiral perturbation theory

   Jack Laiho🇺🇸

   An unquenched calculation of the form factor for $B\to D^{\ast }l\nu$ is needed to improve the determination of $|V_{cb}|$. The MILC lattices, computed with a 2+1 improved staggered action for the light quarks, are well suited to this purpose. The relevant staggered chiral perturbation theory (SChPT) must be known in order to correctly account for the "taste" breaking discretization effects associated with the staggered quarks to NLO in $1/m_{D^{\ast }}$. This SChPT calculation is presented.

   hep-latPoS(2006)·3 citations
3. 03*

   Determination of the spin-dependent potentials with the multi-level algorithm

   Miho Koma🇩🇪 · Yoshiaki Koma🇩🇪 · Hartmut Wittig🇩🇪

   The spin-dependent corrections to the static interquark potential are relevant to describing the fine and hyper-fine splittings of the heavy quarkonium spectra. We investigate these corrections in SU(3) lattice gauge theory with the Polyakov loop correlation function as the quark source by applying the multi-level algorithm. We observe remarkably clean signals for the spin-dependent potentials up to intermediate distances.

   hep-latPoS(2006)·15 citations
4. 04*

   Charmonium Spectrum on dynamical anisotropic lattices

   K. J. Juge🇮🇪 · A. O'Cais🇮🇪 · M. B. Oktay🇮🇪 · M. J. Peardon🇮🇪 · S. M. Ryan🇮🇪

   We present a first study of the charmonium spectrum on N_f=2 dynamical, anisotropic lattices. We take advantage of all-to-all quark propagators to build spatially extended interpolating operators to increase the overlap with states not easily accessible with point propagators such as radially excited states of eta_c, psi, and chi_c, D-waves and hybrid states.

   hep-latPoS(2006)·11 citations
5. 05*

   The axial charge of the nucleon on the lattice and in chiral perturbation theory

   A. Ali Khan · M. Göckeler🇩🇪 · P. Hägler🇩🇪 · T. R. Hemmert🇩🇪 · R. Horsley🇬🇧 · A. C. Irving🇬🇧 · D. Pleiter🇩🇪 · P. E. L. Rakow🇬🇧 · A. Schäfer🇩🇪 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · T. Wollenweber🇩🇪 · J. M. Zanotti🇬🇧

   We present recent Monte Carlo data for the axial charge of the nucleon obtained by the QCDSF-UKQCD collaboration for N_f=2 dynamical quarks. We compare them with formulae from chiral perturbation theory in finite and infinite volume and find a remarkably consistent picture.

   hep-latPoS(2006)·6 citations
6. 06*

   Strange quark mass from e+e- revisited and present status of light quark masses

   Stephan Narison (CNRS-Montpellier)🇫🇷

   We reconsider the determinations of the strange quark mass m_s from e+e- into hadrons data using a new combination of FESR and revisiting the existing tau-like sum rules by including non-resonant contributions to the spectral functions. To order alpha_s^3 and including the tachyonic gluon mass lambda^2 contribution, which phenomenologically parametrizes the UV renormalon effect into the PT series, we obtain the invariant mass m_s=(119 +- 17)MeV leading to: m_s(2 GeV)=(104+- 15)MeV. Combining this value with the recent and independent phenomenological determinations from some other channels, to order alpha_s^3 and including lambda^2, we deduce the weighted average: m_s (2 GeV)=(96.1 +- 4.8)MeV . The positivity of the spectral functions in the (pseudo)scalar [resp. vector] channels leads to the lower [resp. upper] bounds of m_s(2 GeV): (71 +- 4) MeV < m_s(2 GeV) < (151 +- 14) MeV, to order alpha_s^3. Using the ChPT mass ratio r_3 = 2m_s/(m_u+m_d)=24.2 +- 1.5, and the average value of m_s, we deduce: (m_u+m_d)(2 GeV)=(7.9 +- 0.6) MeV, consistent with the pion sum rule result, which, combined with the ChPT value for m_u/m_d, gives: m_d(2 GeV)=(5.1 +- 0.4)MeV and m_u(2 GeV)=(2.8 +- 0.2)MeV. Finally, using (m_u+m_d) from the pion sum rule and the average value of m_s (without the pion sum rule), the method gives: r_3= 23.5 +- 5.8 in perfect agreement with the ChPT ratio, indicating the self-consistency of the sum rule results. Using the value: m_b(m_b)=(4.23 +- 0.06) GeV, we also obtain the model-building useful scale-independent mass ratio: m_b/m_s=50 +- 3.

   ↳ hep-phhep-exhep-latnucl-thPRD(2006)·87 citations
7. 07*

   Collective non-Abelian instabilities in a melting Color Glass Condensate

   Paul Romatschke🇩🇪 · Raju Venugopalan🇺🇸

   We present first results for 3+1-D simulations of SU(2) Yang-Mills equations for matter expanding into the vacuum after a heavy ion collision. Violations of boost invariance cause a Weibel instability leading soft modes to grow with proper time $\tau$ as $\exp (\Gamma \sqrt{g^2\mu \tau })$, where $g^2\mu$ is a scale arising from the saturation of gluons in the nuclear wavefunction. The scale for the growth rate $\Gamma$ is set by a plasmon mass, defined as ${\omega }_{\mathrm{pl}}={\kappa }_0\sqrt{\frac{g^2\mu }{\tau }}$, generated dynamically in the collision. We compare the numerical ratio $\Gamma /{\kappa }_0$ to the corresponding value predicted by the Hard Thermal Loop formalism for anisotropic plasmas.

   ↳ hep-phhep-latnucl-thPRL(2006)·285 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.