11,100 research outputs found
Low-energy particle physics and chiral extrapolations
In this review I discuss the role of chiral extrapolations for the
determination of several phenomenologically relevant quantities, including
light quark masses, meson decay constants and the axial charge of the nucleon.
In particular, I investigate whether chiral extrapolations are sufficiently
controlled in order to rightfully claim the accuracy which is quoted in recent
compilations of these quantities. While this is the case for the masses of the
light quarks and the ratio fK/fpi of decay constants, small inconsistencies in
the chiral and continuum behaviour of individual decay constants fK and fpi, as
well as the hadronic radii r0, r1 remain and must be clarified. In the case of
the nucleon axial charge, gA, the chiral behaviour is still poorly understood
due to the presence of other systematic effects.Comment: 14 pages, plenary talk presented at the XXIX International Symposium
on Lattice Field Theory - Lattice 2011 July 10-16, 2011, Squaw Valley, Lake
Tahoe, Californi
String Breaking in SU(2) Yang Mills Theory with Adjoint Sources
We compute the static potential in three-dimensional SU(2) Yang Mills Theory
with adjoint sources using numerical simulations. By employing a variational
approach involving string and gluelump operators, we obtain clear evidence for
string breaking in the adjoint potential. The breaking scale r_b is computed
and extrapolated to the continuum limit. The result in units of the scalar
glueball mass is r_b*m_G = 10.3 +/- 1.5. We also resolve the structure of
higher excitations of the flux-tube and gluelumps. Furthermore we discuss the
implications of our findings for the case of the four-dimensional theory.Comment: 16 pages, 5 postscript figures, LaTe
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
- …