5,405 research outputs found
Quark mass dependence of the pseudoscalar hairpin vertex
In a recent investigation of chiral behavior in quenched lattice QCD, the
flavor-singlet pseudoscalar ``hairpin'' vertex associated with the eta prime
mass was studied for pion masses ranging from approximately 275 to 675 MeV.
Throughout this mass range, the quark-disconnected pseudoscalar correlator is
well-described by a pure double-pion-pole diagram with a p^2 independent mass
insertion. The residue of the double pole was found to exhibit a significant
quark mass dependence, evidenced by a negative slope of the effective mass
insertion (m_0^{eff})^2 as a function of m_{\pi}^2. It has been observed by
Sharpe that, with a consistent NLO calculation in quenched chiral perturbation
theory, this mass dependence is uniquely predicted in terms of the single-pole
coefficient \alpha_{\Phi} and the Leutwyler parameter L_5. Since \alpha_{\Phi}
is found to be approximately zero, the chiral slope of the double-pole residue
determines a value for L_5. This provides a consistency check between the
chiral slope of the hairpin mass insertion and that of the pion decay constant.
We investigate the consistency of these mass dependences in our Monte Carlo
results at two values of lattice spacing. Within statistics, the slopes are
found to be consistent with the Q\chiPT prediction, confirming that the
observed negative slope of m_0^{eff} arises as an effect of the L_5 Leutwyler
term.Comment: 4 pages, 1 figure, LaTe
QED2 as a testbed for interpolations between quenched and full QCD
Lattice QED2 with the Wilson formulation of fermions is used as a convenient
model system to study artifacts of the quenched approximation on a finite
lattice. The quenched functional integral is shown to be ill-defined in this
system as a consequence of the appearance of exactly real modes for physical
values of the fermion mass.
The location and frequency of such modes is studied as a function of lattice
spacing, lattice volume, topological charge and improved action parameters. The
efficacy of the recently proposed modified quenched approximation is examined,
as well as a new approach to the interpolation from the quenched to full
dynamical theory employing a truncated form of the fermion determinant.Comment: Talk presented by A. Duncan at LATTICE97 (theoretical developments
Perspectives for heavy flavour production in ATLAS
The prospects of making charm and bottom production measurements with the ATLAS experiment are presented
Interpretation and Legal Theory, Andrei Marmor
Book review of Interpretation and Legal Theory by Andrei Marmor and published by Clarendon Press (Oxford), 1992. (193 pp.
Physical Effects of Infrared Quark Eigenmodes in LQCD
A truncated determinant algorithm is used to study the physical effects of
the quark eigenmodes associated with eigenvalues below 400 MeV. This initial
study focuses on coarse lattices (with O(a^2) improved gauge action), light
internal quark masses and large physical volumes. Four bellwether full QCD
processes are discussed: topological charge distributions, the eta prime
propagator, string breaking as observed in the static energy and the rho decay
into two pions.Comment: LATTICE99(Confinement); 3pgs(Latex), 4figs.(eps
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