Tue·Sep 21, 2004Tuesday·September 21, 2004

1. 01*

   Nucleon Decay Matrix Elements with N_f=0 and 2 Domain-Wall Quarks

   Yasumichi Aoki (for the RBC collaboration)🇩🇪

   The nucleon decay matrix elements of three-quark operators are calculated with domain-wall fermions. Operators are renormalized non-perturbatively to match the MS bar (NDR) scheme at NLO. Quenched simulation studies involve both direct measurement of the matrix elements and the chiral Lagrangian parameters, alpha and beta. We also report on the dynamical quark effects on these parameters.

   hep-lathep-phNucl.Phys.B Proc.Suppl.(2005)·6 citations
2. 02*

   Rough Gauge Fields, Smearing and Domain Wall Fermions

   Meifeng Lin🇺🇸

   At a fixed lattice spacing, as determined by say m_\rho, adding additional fermion flavors to a dynamical simulation produces rougher gauge field configurations at the lattice scale. For domain wall fermions, these rough configurations lead to larger residual chiral symmetry breaking and larger values for the residual masses, m_{res}. We discuss ongoing attempts to reduce chiral symmetry breaking for N_f = 3 dynamical domain wall fermion simulations by different smoothing choices for the gauge fields.

   hep-latNucl.Phys.B Proc.Suppl.(2005)·1 citation
3. 03*

   Semileptonic D->pi/K and B->pi/D decays in 2+1 flavor lattice QCD

   M. Okamoto🇺🇸 · C. Aubin🇺🇸 · C. Bernard🇺🇸 · C. DeTar🇺🇸 · M. Di Pierro🇺🇸 · A.X. El-Khadra🇺🇸 · Steven Gottlieb🇺🇸 · E.B. Gregory🇺🇸 · U.M. Heller🇺🇸 · J. Hetrick🇺🇸 · A.S. Kronfeld🇺🇸 · P.B. Mackenzie🇺🇸 and 8 other authors

   We present results for form factors of semileptonic decays of $D$ and $B$ mesons in 2+1 flavor lattice QCD using the MILC gauge configurations. With an improved staggered action for light quarks, we successfully reduce the systematic error from the chiral extrapolation. The results for $D$ decays are in agreement with experimental ones. The results for B decays are preliminary. Combining our results with experimental branching ratios, we then obtain the CKM matrix elements $|V_{cd}|$, $|V_{cs}|$, $|V_{cb}|$ and $|V_{ub}|$. We also check CKM unitarity, for the first time, using only lattice QCD as the theoretical input.

   hep-latNucl.Phys.B Proc.Suppl.(2005)·235 citations
4. 04*

   A scaling study of the step scaling function of quenched QCD with improved gauge actions

   CP-PACS Collaboration: S. Takeda🇯🇵 · S. Aoki🇯🇵 · M. Fukugita🇯🇵 · K-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · T. Kaneko🇯🇵 · Y. Kuramashi🇯🇵 · M. Okawa🇯🇵 · Y. Taniguchi🇯🇵 · A. Ukawa🇯🇵 · T. Yoshié🇯🇵

   We study the scaling behavior of the step scaling function for SU(3) gauge theory, employing the Iwasaki gauge action and the Luescher-Weisz gauge action. In particular, we test the choice of boundary counter terms and apply a perturbative procedure for removal of lattice artifacts for the simulation results in the extrapolation procedure. We confirm the universality of the step scaling functions at both weak and strong coupling regions. We also measure the low energy scale ratio with the Iwasaki action, and confirm its universality.

   hep-latNucl.Phys.B Proc.Suppl.(2005)·0 citations
5. 05*

   Mobius Fermions: Improved Domain Wall Chiral Fermions

   Richard C. Brower🇺🇸 · Hartmut Neff🇺🇸 · Kostas Orginos🇺🇸

   A new class of domain wall fermions is defined that interpolates between Shamir's and Boriçi's form without increasing the number of Dirac applications per CG iteration. This class represents a full (real) Möbius transformation of the Wilson kernel. Simulations on quenched Wilson lattices with $\beta =6.0$ show that the number of lattice sites ($L_s$) in the fifth dimension can be reduced by a factor of 2 or more at fixed value of chiral symmetry violations measured by the residual mass ($m_{res}$).

   hep-latNucl.Phys.B Proc.Suppl.(2005)·122 citations
6. 06*

   Electromagnetic Hadronic Form-Factors

   Robert G. Edwards (for the Lattice Hadron Physics Collaboration)🇺🇸

   We present a calculation of the nucleon electromagnetic form-factors as well as the pion and rho to pion transition form-factors in a hybrid calculation with domain wall valence quarks and improved staggered (Asqtad) sea quarks.

   hep-latNucl.Phys.B Proc.Suppl.(2005)·7 citations
7. 07*

   Chiral Extension of Lattice Gauge Theory

   Richard C. Brower🇺🇸

   Two approaches are presented to coupling explicit Goldstone modes to $N_f$ flavors of massless quarks preserving exact $SU(N_f)\times SU(N_f)$ chiral symmetry on the lattice. The first approach is a generalization a chiral extension to QCD (aka XQCD) proposed by Brower, Shen and Tan consistent with the Ginsparg-Wilson relation. The second approach based on the Callan,Coleman, Wess and Zumino coset construction has a real determinant atzero quark axial coupling, $g_A=0$.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
8. 08*

   Penta-Quark Anti-Decuplet in Anisotropic Lattice QCD

   N. Ishii (Tokyo Inst. Tech.)🇯🇵 · T. Doi (RIKEN BNL)🇺🇸 · H. Iida (Tokyo Inst. Tech.)🇯🇵 · M. Oka (Tokyo Inst. Tech.)🇯🇵 · F. Okiharu (Nihon Univ.)🇯🇵 · H. Suganuma (Tokyo Inst. Tech.)🇯🇵

   The penta-quark(5Q) Theta^+(1540) is studied in anisotropic lattice QCD with renormalized anisotropy a_s/a_t=4 for a high-precision measurement. Both the positive and the negative parity 5Q baryons are studied using a non-NK type interpolating field with I=0 and J=1/2. After the chiral extrapolation, the lowest positive parity state is found at m_{Theta}\simeq 2.25 GeV, which is too heavy to be identified with Theta^+(1540). In the negative parity channel, the lowest energy state is found at m_{Theta}\simeq 1.75 GeV. Although it is rather close to the empirical value, it is considered to be an NK scattering state rather than a localized resonance state.

   hep-latNucl.Phys.B Proc.Suppl.(2005)·5 citations
9. 09*

   The N to Delta electromagnetic transition form factors from Lattice QCD

   C. Alexandrou (Univ. of Cyprus)🇨🇾 · Ph. de Forcrand (CERN & ETH Zurich)🇨🇭 · H. Neff (Boston Univ.)🇺🇸 · J. W. Negele (MIT)🇺🇸 · W. Schroers (MIT)🇺🇸 · A.Tsapalis (Univ. of Cyprus)🇨🇾

   The magnetic dipole, the electric quadrupole and the Coulomb quadrupole amplitudes for the transition \gamma N\to \Delta are calculated in quenched lattice QCD at \beta=6.0 with Wilson fermions. Using a new method combining an optimal combination of interpolating fields for the $\Delta$ and an overconstrained analysis, we obtain statistically accurate results for the dipole form factor and for the ratios of the electric and Coulomb quadrupole amplitudes to the magnetic dipole amplitude, R_{EM} and R_{SM}, up to momentum transfer squared 1.5 GeV^2. We show for the first time using lattice QCD that both R_{EM} and R_{SM} are non-zero and negative, in qualitative agreement with experiment and indicating the presence of deformation in the N- Delta system.

   hep-latnucl-exnucl-thPRL(2005)·119 citations
10. 10*

    Chiral perturbation theory at non-zero lattice spacing

    Oliver Baer

    A review of chiral perturbation theory for lattice QCD at non-zero lattice spacing is given.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·37 citations
11. 11*

    Light hadron spectrum in 2+1 flavor full QCD by CP-PACS and JLQCD Collaborations

    T. Ishikawa🇯🇵 · S. Aoki🇯🇵 · M. Fukugita🇯🇵 · S. Hashimoto🇯🇵 · K-I. Ishikawa🇯🇵 · N. Ishizuka🇯🇵 · Y. Iwasaki🇯🇵 · K. Kanaya🇯🇵 · T. Kaneko🇯🇵 · Y. Kuramashi🇯🇵 · M. Okawa🇯🇵 · T. Onogi🇯🇵 and 4 other authors

    CP-PACS and JLQCD Collaborations are carrying out a joint project of the 2+1 flavor full QCD with the RG-improved gauge action and the non-perturbatively $\mathcal{O}(a)$-improved Wilson quark action. This simulation removes quenching effects of all three light quarks, which is the last major uncertainty in lattice QCD. In this report we present our results for the light meson spectrum and quark masses on a $20^3\times 40$ lattice at the lattice spacing $a\simeq 0.10$ fm.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·26 citations
12. 12*

    The gluon and ghost propagator and the influence of Gribov copies

    A. Sternbeck🇩🇪 · E.-M. Ilgenfritz🇩🇪 · M. Mueller-Preussker🇩🇪 · A. Schiller🇩🇪

    The dependence of the Landau gauge gluon and ghost propagators on the choice of Gribov copies is studied in pure SU(3) lattice gauge theory. Whereas the influence on the gluon propagator is small, the ghost propagator becomes clearly affected by the copies in the infrared region. We compare our data with the infrared exponents predicted by the Dyson-Schwinger equation approach

    hep-latNucl.Phys.B Proc.Suppl.(2005)·26 citations
13. 13*

    Chiral dynamics in QCD at finite chemical potential

    Sourendu Gupta🇮🇳 · R. Ray🇮🇳

    We present the renormalized Taylor expansion of the chiral condensate with chemical potential. The relation with the Taylor coefficients of meson susceptibilities and the quark mass dependence of the quark number susceptibilities are obtained through chiral Ward identities and Maxwell relations. The continuum limit is obtained in quenched and two flavour QCD. In Nf=2 QCD, the quadratic response coefficients (QRCs) of the chiral condensate to chemical potential indicate that pion fluctuations decrease at finite chemical potential toward the critical end point. We discuss how these observables can be used to test other features of the QCD phase diagram.

    hep-lathep-phnucl-exnucl-thPRD(2004)·21 citations
14. 14*

    Higher Loop Results for the Plaquette, Using the Clover and Overlap Actions

    A. Athenodorou🇨🇾 · H. Panagopoulos🇨🇾 · A. Tsapalis (University of Cyprus, Nicosia)🇨🇾

    We calculate the perturbative value of the free energy in QCD on the lattice. This quantity is directly related to the average plaquette. Our calculation is done to 3 loops using the clover action for fermions; the results are presented for arbitrary values of the clover coefficient, and for a wide range of fermion masses. In addition, we calculate the 2 loop result for the same quantity, using the overlap action.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·4 citations
15. 15*

    Charmonium Spectrum from Quenched QCD with Overlap Fermions

    S. Tamhankar🇺🇸 · A. Alexandru🇺🇸 · Y. Chen🇨🇳 · S. J. Dong🇺🇸 · T. Draper🇺🇸 · I. Horvath🇺🇸 · F. X. Lee🇺🇸 · K. F. Liu🇺🇸 · N. Mathur🇺🇸 · J. B. Zhang🇦🇺

    We present preliminary results using overlap fermions for the charmonium spectrum, in particular for hyperfine splitting. Simulations are performed on $16^3\times 72$ lattices, with Wilson gauge action at $\beta =6.3345$. Depending on how the scale is set, we obtain 104(5) MeV (using $1\bar{P}-1\bar{S}$) or 88(4) MeV (using $r_0$=0.5 fm) for the hyperfine splitting.

    hep-latNucl.Phys.B Proc.Suppl.(2005)·3 citations
16. 16*

    Introduction to Nonequilibrium Quantum Field Theory

    J. Berges🇩🇪

    There has been substantial progress in recent years in the quantitative understanding of the nonequilibrium time evolution of quantum fields. Important topical applications, in particular in high energy particle physics and cosmology, involve dynamics of quantum fields far away from the ground state or thermal equilibrium. In these cases, standard approaches based on small deviations from equilibrium, or on a sufficient homogeneity in time underlying kinetic descriptions, are not applicable. A particular challenge is to connect the far-from-equilibrium dynamics at early times with the approach to thermal equilibrium at late times. Understanding the ``link'' between the early- and the late-time behavior of quantum fields is crucial for a wide range of phenomena. For the first time questions such as the explosive particle production at the end of the inflationary universe, including the subsequent process of thermalization, can be addressed in quantum field theory from first principles. The progress in this field is based on efficient functional integral techniques, so-called n-particle irreducible effective actions, for which powerful nonperturbative approximation schemes are available. Here we give an introduction to these techniques and show how they can be applied in practice. Though we focus on particle physics and cosmology applications, we emphasize that these techniques can be equally applied to other nonequilibrium phenomena in complex many body systems.

    ↳ hep-phastro-phhep-lathep-th+2AIP Conf.Proc.(2004)·576 citations
17. 17*

    N-ality and topology at finite temperature

    L. Del Debbio (1)🇨🇭 · H. Panagopoulos (2)🇨🇾 · E. Vicari (3) ((1) CERN, Department of Physics, (2) University of Cyprus, (3) Universita` di Pisa)🇮🇹

    We study the spectrum of confining strings in SU(3) pure gauge theory, in different representations of the gauge group. Our results provide direct evidence that the string spectrum agrees with predictions based on n-ality. We also investigate the large-N behavior of the topological susceptibility $\chi$ in four-dimensional SU(N) gauge theories at finite temperature, and in particular across the finite-temperature transition at $T_c$. The results indicate that $\chi$ has a nonvanishing large-N limit for $T<T_c$, as at T=0, and that the topological properties remain substantially unchanged in the low-temperature phase. On the other hand, above the deconfinement phase transition, $\chi$ shows a large suppression. The comparison between the data for N=4 and N=6 hints at a vanishing large-N limit for $T>T_c$.

    ↳ hep-thhep-latNucl.Phys.B Proc.Suppl.(2005)·2 citations
18. 18*

    Quark Propagation in the Presence of a A_\mu^aA_a^\mu> Condensate

    Xiangdong Li🇺🇸 · C. M. Shakin🇺🇸

    There is a good deal of current interest in the condensate g^2A_\mu^aA_a^\mu> which has recently be shown to be the Landau gauge version of a more general gauge-invariant expression. In the present work we consider quark propagation in the presence of such a condensate which we assume to be present in the vacuum. We describe the vacuum as a random medium of gluon fields. We discuss quark propagation in that medium and show that the quark propagator has no on-mass-shell pole indicating that a quark cannot propagate over extended distances. That is, the quark is a nonpropagating mode in the gluon condensate.

    ↳ nucl-thhep-lathep-phPRD(2004)·13 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.