Fitting Correlated Hadron Mass Spectrum Data

We discuss fitting hadronic Green functions versus time $t$ to extract mass values in quenched lattice QCD. These data are themselves strongly correlated in $t$. With only a limited number of data samples, the method of minimising correlated $\chi^2$ is unreliable. We explore several methods of modelling the correlations among the data set by a few parameters which then give a stable and sensible fit even if the data sample is small. In particular these models give a reliable estimate of the goodness of fit.Comment: 14 pages, Latex text, followed by 3 postscript figures in self-unpacking file. Also available at ftp://suna.amtp.liv.ac.uk/pub/cmi/corfit

Semileptonic Decays of Heavy Mesons with the Fat Clover Action

We are studying a variety of semileptonic decays of heavy-light mesons in an effort to improve the determination of the heavy-quark Standard-Model CKM matrix elements. Our fermion action is a novel, improved ``fat'' clover action that promises to reduce problems with exceptional configurations. Dynamical sea quarks are included in a mixed approach, i.e. we use staggered sea quarks and fat-clover valence quarks. Here we report preliminary results.Comment: LATTICE99(heavyqk) - 3p, 4 Postscript fig

The equation of state with nonzero chemical potential for 2+1 flavors

We present results for the QCD equation of state with nonzero chemical potential using the Taylor expansion method with terms up to sixth order in the expansion. Our calculations are performed on asqtad 2+1 quark flavor lattices at $N_t=4$.Comment: Talk given at the XXV International Symposium on Lattice Field Theory, July 30-4 August 2007, Regensburg, German

Critical Behavior at the Chiral Phase Transition

Quantum chromodynamics with two zero mass flavors is expected to exhibit a phase transition with O(4) critical behavior. Fixing the universality class is important for phenomenology and for facilitating the extrapolation of simulation data to physical quark mass values. At Lattice '96 the Tsukuba and Bielefeld groups reported results from new simulations with dynamical staggered quarks at $N_t = 4$, which suggested a departure from the expected critical behavior. We report observations of similar deviations and discuss efforts in progress to understand this phenomenon.Comment: 3 pp, LaTeX with 6 encapsulated Postscript figures. Lattice '97 proceeding

Heavy-Light Decay Constants: Conclusions from the Wilson Action

We report on the results of a MILC collaboration calculation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios. We discuss the most important errors in more detail than we have elsewhere.Comment: LATTICE98(heavyqk) 3 latex pages and 3 postscript figures. The perturbative correction calculated by Kuramashi has been adjusted to take into account the fact that we match to the continuum at the kinetic mass of the heavy meson, not the pole mass. This produces a 2 to 4 MeV change in final results for decay constants, and has negligible effect on decay constant ratio