Fri·Sep 19, 2003Friday·September 19, 2003

1. 01*

   Thermal Effects on the Condensates of Chiral Order Parameters, the Quark Condensate and the Quark Gluon Mixed Condensate, and Chiral Restoration from Lattice QCD

   Takumi Doi (1) · Noriyoshi Ishii (2) · Makoto Oka (1) · Hideo Suganuma (1) ((1) Tokyo Inst. Tech, (2) Wako, RIKEN)

   We study the quark-gluon mixed condensate g<\bar{q} \sigma G q> using the SU(3)c lattice QCD with the Kogut-Susskind fermion at the quenched level. We perform the first but accurate measurement of the thermal effects on the mixed condensate in lattice QCD at \beta = 6.0 with 16^3 * Nt (Nt=16,12,10,8,6,4), \beta = 6.1 with 20^3 * Nt (Nt=20,12,10,8,6), and \beta = 6.2 with 24^3 * Nt (Nt=24,16,12,10,8). At each temperature, the lattice calculation is carried out with high statistics using more than 100 gauge configurations. In particular, about 1000 gauge configurations are used near the critical temperature T_c. The chiral extrapolation is done from the lattice result with the current-quark mass of m_q = 21,36,52 MeV. While the thermal effects on both of the mixed condensate and the quark condensate are very weak except for the vicinity of T_c, both the condensates suddenly vanish around T_c \simeq 280 MeV, which indicates strong chiral restoration near T_c. To compare the thermal effects on the two condensates, we analyze the ratio m_0^2 = g<\bar{q} \sigma G q>/ <\bar{q}q>, and find that m_0^2 is almost independent of the temperature, even in the very vicinity of T_c. This means that these two different condensates obey the same critical behavior, and this nontrivial similarity between them would impose constraints on the chiral structure of the QCD vacuum near T_c.

   hep-lathep-phnucl-thNucl.Phys.B Proc.Suppl.(2004)·3 citations
2. 02*

   Comparison of Fat7-bar and HYP fat links

   S. O. Bilson-Thompson🇰🇷 · W. Lee🇰🇷

   We study various methods of constructing fat links based upon the HYP (by Hasenfratz & Knechtli) and Fat7-bar (by W. Lee) algorithms. We present the minimum plaquette distribution for these fat links. This enables us to determine which algorithm is most effective at reducing the spread of plaquette values.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·1 citation
3. 03*

   Pion parton distribution functions from lattice QCD

   I. Wetzorke🇩🇪 · M. Guagnelli🇮🇹 · K. Jansen🇩🇪 · F. Palombi🇮🇹 · R. Petronzio🇮🇹 · A. Shindler🇩🇪

   We report on recent results for the pion matrix element of the twist-2 operator corresponding to the average momentum of non-singlet quark densities. For the first time finite volume effects of this matrix element are investigated and come out to be surprisingly large. We use standard Wilson and non-perturbatively improved clover actions in order to control better the extrapolation to the continuum limit. Moreover, we compute, fully non-perturbatively, the renormalization group invariant matrix element, which allows a comparison with experimental results in a broad range of energy scales. Finally, we discuss the remaining uncertainties, the extrapolation to the chiral limit and the quenched approximation.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·2 citations
4. 04*

   Computational Aspects of Lattice QCD

   Tereza Mendes🇧🇷

   Monte Carlo simulations applied to the lattice formulation of quantum chromodynamics (QCD) enable a study of the theory from first principles, in a nonperturbative way. After over two decades of developments in the methodology for this study and with present-day computers in the teraflops range, lattice-QCD simulations are now able to provide quantitative predictions with errors of a few percent. This means that these simulations will soon become the main source of theoretical results for comparison with experiments in physics of the strong interactions. It is therefore an important moment for the beginning of Brazilian participation in the field.

   hep-lat1 citation
5. 05*

   Matrix elements of DI=3/2 K-->pi pi decays

   Ph. Boucaud🇫🇷 · V. Gimenez🇪🇸 · C.-J.D. Lin🇺🇸 · V. Lubicz🇮🇹 · G. Martinelli🇮🇹 · M. Papinutto🇩🇪 · C.T. Sachrajda🇬🇧

   We present a numerical computation of matrix elements of DI=3/2 K-->pi pi decays by using Wilson fermions. In order to extrapolate to the physical point we work at unphysical kinematics and we resort to Chiral Perturbation Theory at the next-to-leading order. In particular we explain the case of the electroweak penguins O_{7,8} which can contribute significantly in the theoretical prediction of epsilon'/epsilon. The study is done at beta=6.0 on a 24^3x64 lattice.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·3 citations
6. 06*

   Studying the role of the 't Hooft interaction in QCD, by means of lattice simulations

   P. Faccioli🇮🇹 · T.A. DeGrand🇺🇸

   We report on a recent investigation on the dynamics of light quarks, at intermediate and low energy. By measuring some appropriate correlation functions on the lattice, it is possible to probe the Dirac and flavor structure of the non-perturbative quark-quark interaction and look directly for signatures of the 't Hooft Lagrangian. Results obtained with chiral fermions strongly support the instanton picture and the phenomenological parameters of the Instanton Liquid Model

   hep-latNucl.Phys.B Proc.Suppl.(2004)·0 citations
7. 07*

   Dynamics of Phase Transitions by Hysteresis Methods I

   Bernd A. Berg🇺🇸 · Urs M. Heller🇺🇸 · Hildegard Meyer-Ortmanns🇩🇪 · Alexander Velytsky🇺🇸

   In studies of the QCD deconfining phase transition or crossover by means of heavy ion experiments, one ought to be concerned about non-equilibrium effects due to heating and cooling of the system. Motivated by this, we look at hysteresis methods to study the dynamics of phase transitions. Our systems are temperature driven through the phase transition using updating procedures in the Glauber universality class. Hysteresis calculations are presented for a number of observables, including the (internal) energy, properties of Fortuin-Kasteleyn clusters and structure functions. We test the methods for 2d Potts models, which provide a rich collection of phase transitions with a number of rigorously known properties. Comparing with equilibrium configurations we find a scenario where the dynamics of the transition leads to a spinodal decomposition which dominates the statistical properties of the configurations. One may expect an enhancement of low energy gluon production due to spinodal decomposition of the Polyakov loops, if such a scenario is realized by nature.

   hep-latPRD(2004)·16 citations
8. 08*

   HQET with chiral symmetry on the lattice

   Damir Becirevic🇫🇷 · Juan Reyes🇮🇹

   We show that by combining the static heavy quark action with the Neuberger action for the light quark, the renormalisation of the heavy-light bilinear and four-quark operators, computed on the lattice, becomes highly simplified: all the heavy-light bilinears get renormalised by a single multiplicative constant, whereas the renormalisation of the complete set of parity even dB=2 four-quark operators involves only four independent constants. The relevant (matching) constants are computed at NLO in perturbation theory and are presented here.

   hep-lathep-phNucl.Phys.B Proc.Suppl.(2004)·21 citations
9. 09*

   Hadronic Matrix Elements for Kaons

   Johan Bijnens (Lund)🇸🇪 · Elvira Gamiz (Granada)🇪🇸 · Joaquim Prades (Granada)🇪🇸

   We review some work done by us calculating matrix elements for Kaons. Emphasis is put on the matrix elements which are relevant to predict non-leptonic Kaon CP violating observables. In particular, we recall our results for the \hat B_K parameter which governs the \bar{K^0}-K^0 mixing and update our results for epsilon'_K including estimated all-higher-order CHPT corrections and the new results from recent analytical calculations of the \Delta I=3/2 component. Some comments on future prospects on calculating matrix elements for Kaons are also added.

   ↳ hep-phhep-exhep-latNucl.Phys.B Proc.Suppl.(2004)·14 citations
10. 10*

    Numerical results on the Non-commutative \lambda \phi^4 Model

    W. Bietenholz🇩🇪 · F. Hofheinz🇩🇪 · J. Nishimura🇯🇵

    The UV/IR mixing in the \lambda \phi^4 model on a non-commutative (NC) space leads to new predictions in perturbation theory, including Hartree-Fock type approximations. Among them there is a changed phase diagram and an unusual behavior of the correlation functions. In particular this mixing leads to a deformation of the dispersion relation. We present numerical results for these effects in d=3 with two NC coordinates.

    ↳ hep-thhep-latNucl.Phys.B Proc.Suppl.(2004)·15 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.