533 research outputs found
Non-perturbative Heavy Quark Effective Theory: a test and its matching to QCD
We give an introduction to the special problems encountered in a treatment of
HQET beyond perturbation theory in the gauge coupling constant.
In particular, we report on a recent test of HQET as an effective theory for
QCD and discuss how HQET can be implemented on the lattice including the
non-perturbative matching of the effective theory to QCD.Comment: 12 pages, Late
Non-perturbative Heavy Quark Effective Theory: Introduction and Status
We give an introduction to Heavy Quark Effective Theory (HQET). Our emphasis
is on its formulation non-perturbative in the strong coupling, including the
non-perturbative determination of the parameters in the HQET Lagrangian. In a
second part we review the present status of HQET on the lattice, largely based
on work of the ALPHA collaboration in the last few years. We finally discuss
opportunities and challenges.Comment: 31 pages, 15 figures, Contribution to the Proceedings of the Final
Meeting of DFG SFB-TR-9 (Durbach, Germany, Sept. 2014), to appear in Nucl.
Phys. (Proc. Suppl.
New Perspectives for B-Physics from the Lattice
We give an introduction to the problems faced on the way to a reliable
lattice QCD computation of B-physics matrix elements. In particular various
approaches for dealing with the large scale introduced by the heaviness of the
b-quark are mentioned and promising recent achievements are described. We
present perspectives for future developments.Comment: Invited talk at the XXIII Physics in Collisions Conference (PIC03),
Zeuthen, Germany, June 2003, 15 pages LaTeX. PSN FRAT07. Updated references
and result of ref.[40
Fundamental parameters of QCD
The theory of strong interactions, QCD, is described in terms of a few
parameters, namely the strong coupling constant alpha_s and the quark masses.
We show how these parameters can be determined reliably using computer
simulations of QCD on a space-time lattice, and by employing a finite-size
scaling method, which allows to trace the energy dependence of alpha_s and
quark masses over several orders of magnitude. We also discuss methods designed
to reduce the effects of finite lattice spacing and address the issue of
computer resources required.Comment: Contribution to proceedings of NIC Symposium 2001, 13 pages, 7
figures, uses nic-series.cl
Non-perturbative computation of the strong coupling constant on the lattice
We review the long term project of the ALPHA collaboration to compute in QCD
the running coupling constant and quark masses at high energy scales in terms
of low energy hadronic quantities. The adapted techniques required to
numerically carry out the required multiscale non-perturbative calculation with
our special emphasis on the control of systematic errors are summarized. The
complete results in the two dynamical flavor approximation are reviewed and an
outlook is given on the ongoing three flavor extension of the programme with
improved target precision.Comment: 30 pages, 20 figures, Contribution to the Proceedings of the Final
Meeting of DFG SFB-TR-9 (Durbach, Germany, Sept. 2014), to appear in Nucl.
Phys. (Proc. Suppl.)
Large scaling and factorization in Yang-Mills theory
We present results for Wilson loops smoothed with the Yang-Mills gradient
flow and matched through the scale . They provide renormalized and precise
operators allowing to test the scaling both at finite lattice spacing
and in the continuum limit. Our results show an excellent scaling up to . Additionally, we obtain a very precise non-perturbative confirmation of
factorization in the large limit.Comment: 8 pages, 7 figures. Presented at the 35th International Symposium on
Lattice Field Theory, Granada, Spain, 18-24 June 2017 (Lattice 2017
Large scaling and factorization in SU() Yang-Mills gauge theory
The large limit of SU() gauge theories is well understood in
perturbation theory. Also non-perturbative lattice studies have yielded
important positive evidence that 't Hooft's predictions are valid. We go far
beyond the statistical and systematic precision of previous studies by making
use of the Yang-Mills gradient flow and detailed Monte Carlo simulations of
SU() pure gauge theories in 4 dimensions. With results for we
study the limit and the approach to it. We pay particular attention to
observables which test the expected factorization in the large limit. The
investigations are carried out both in the continuum limit and at finite
lattice spacing. Large scaling is verified non-perturbatively and with high
precision; in particular, factorization is confirmed. For quantities which only
probe distances below the typical confinement length scale, the coefficients of
the expansion are of , but we found that large (smoothed)
Wilson loops have rather large corrections. The exact size
of such corrections does, of course, also depend on what is kept fixed when the
limit is taken.Comment: 25 pages, 11 figure
Topological susceptibility and the sampling of field space in lattice QCD simulations
We present a measurement of the topological susceptibility in two flavor QCD.
In this observable, large autocorrelations are present and also sizable cutoff
effects have to be faced in the continuum extrapolation. Within the statistical
accuracy of the computation, the result agrees with the expectation from
leading order chiral perturbation theory.Comment: 22 pages, 7 figures; References added, minor clarifications in the
text, results unchange
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