8,411 research outputs found
Light Hadron Spectrum in Quenched Lattice QCD with Staggered Quarks
Without chiral extrapolation, we achieved a realistic nucleon to (\rho)-meson
mass ratio of (m_N/m_\rho = 1.23 \pm 0.04 ({\rm statistical}) \pm 0.02 ({\rm
systematic})) in our quenched lattice QCD numerical calculation with staggered
quarks. The systematic error is mostly from finite-volume effect and the
finite-spacing effect is negligible. The flavor symmetry breaking in the pion
and (\rho) meson is no longer visible. The lattice cutoff is set at 3.63 (\pm)
0.06 GeV, the spatial lattice volume is (2.59 (\pm) 0.05 fm)(^3), and bare
quarks mass as low as 4.5 MeV are used. Possible quenched chiral effects in
hadron mass are discussed.Comment: 5 pages and 5 figures, use revtex
Holographic classification of Topological Insulators and its 8-fold periodicity
Using generic properties of Clifford algebras in any spatial dimension, we
explicitly classify Dirac hamiltonians with zero modes protected by the
discrete symmetries of time-reversal, particle-hole symmetry, and chirality.
Assuming the boundary states of topological insulators are Dirac fermions, we
thereby holographically reproduce the Periodic Table of topological insulators
found by Kitaev and Ryu. et. al, without using topological invariants nor
K-theory. In addition we find candidate Z_2 topological insulators in classes
AI, AII in dimensions 0,4 mod 8 and in classes C, D in dimensions 2,6 mod 8.Comment: 19 pages, 4 Table
Chiral corrections to the axial charges of the octet baryons from quenched QCD
We calculate one-loop correction to the axial charges of the octet baryons
using quenched chiral perturbation theory, in order to understand chiral
behavior of the axial charges in quenched approximation to quantum
chromodynamics (QCD). In contrast to regular behavior of the full QCD chiral
perturbation theory result, , we find
that the quenched chiral perturbation theory result,
, is
singular in the chiral limit.Comment: standard LaTeX, 16 pages, 4 epsf figure
Ambiguities of neutrino(antineutrino) scattering on the nucleon due to the uncertainties of relevant strangeness form factors
Strange quark contributions to neutrino(antineutrino) scattering are
investigated on the nucleon level in the quasi-elastic region. The incident
energy range between 500 MeV and 1.0 GeV is used for the scattering. All of the
physical observable by the scattering are investigated within available
experimental and theoretical results for the strangeness form factors of the
nucleon. In specific, a newly combined data of parity violating electron
scattering and neutrino scattering is exploited. Feasible quantities to be
explored for the strangeness contents are discussed for the application to
neutrino-nucleus scattering.Comment: 17 pages, 7 figures, submit to J. Phys.
Finite-volume two-pion energies and scattering in the quenched approximation
We investigate how L\"uscher's relation between the finite-volume energy of
two pions at rest and pion scattering lengths has to be modified in quenched
QCD. We find that this relation changes drastically, and in particular, that
``enhanced finite-volume corrections" of order and occur at
one loop ( is the linear size of the box), due to the special properties of
the in the quenched approximation. We define quenched pion scattering
lengths, and show that they are linearly divergent in the chiral limit. We
estimate the size of these various effects in some numerical examples, and find
that they can be substantial.Comment: 22 pages, uuencoded, compressed postscript fil
Quenched Chiral Perturbation Theory for Heavy-light Mesons
We formulate quenched chiral perturbation theory for heavy-light mesons
coupled to pions, and calculate the one-loop chiral logarithmic corrections to
, , and . We also calculate these corrections
for ``partially quenched'' theories. In both theories, the chiral logarithms
diverge in the chiral limit, indicating that (partially) quenched theories
should not be used to study this limit. Comparing the chiral logarithms to
those in QCD, we estimate the errors caused by (partial) quenching. By forming
suitable ratios, we can reduce the uncertainties in our estimates.Comment: 22 pages, revtex format, 5 Postscript figure
The QCD spectrum with three quark flavors
We present results from a lattice hadron spectrum calculation using three
flavors of dynamical quarks - two light and one strange, and quenched
simulations for comparison. These simulations were done using a one-loop
Symanzik improved gauge action and an improved Kogut-Susskind quark action. The
lattice spacings, and hence also the physical volumes, were tuned to be the
same in all the runs to better expose differences due to flavor number. Lattice
spacings were tuned using the static quark potential, so as a byproduct we
obtain updated results for the effect of sea quarks on the static quark
potential. We find indications that the full QCD meson spectrum is in better
agreement with experiment than the quenched spectrum. For the 0++ (a0) meson we
see a coupling to two pseudoscalar mesons, or a meson decay on the lattice.Comment: 38 pages, 20 figures, uses epsf. 5/29/01 revision responds to
referee's Comments, changes pion fits and tables, and corrects Fig. 10 and
some minor error
Thermodynamics of Lattice QCD with Chiral 4-Fermion Interactions
We have studied lattice QCD with an additional, irrelevant 4-fermion
interaction having a U(1)xU(1) chiral symmetry, at finite temperatures. Adding
this 4-fermion term allowed us to work at zero quark mass, which would have
otherwise been impossible. The theory with 2 massless staggered quark flavours
appears to have a first order finite temperature phase transition at N_t=4 for
the value of 4-fermion coupling we have chosen, in contrast to what is expected
for 2-flavour QCD. The pion screening mass is seen to vanish below this
transition, only to become massive and degenerate with the sigma (f_0) above
this transition where the chiral symmetry is restored, as is seen by the
vanishing of the chiral condensate.Comment: 23 pages, 11 figure
Thermodynamics of lattice QCD with two light quark flavours on a 16^3 x 8 lattice II
We have extended our earlier simulations of the high temperature behaviour of
lattice QCD with two light flavours of staggered quarks on a
lattice to lower quark mass (m_q=0.00625). The transition from hadronic matter
to a quark-gluon plasma is observed at corresponding to a
temperature of MeV. We present measurements of observables
which probe the nature of the quark-gluon plasma and serve to distinguish it
from hadronic matter. Although the transition is quite abrupt, we have seen no
indications that it is first order.Comment: 23 pages, RevteX, 6 encapsulated postscript figure
Perfect Lattice Actions for Staggered Fermions
We construct a perfect lattice action for staggered fermions by blocking from
the continuum. The locality, spectrum and pressure of such perfect staggered
fermions are discussed. We also derive a consistent fixed point action for free
gauge fields and discuss its locality as well as the resulting static
quark-antiquark potential. This provides a basis for the construction of
(classically) perfect lattice actions for QCD using staggered fermions.Comment: 30 pages, LaTex, 10 figure
- âŠ