289 research outputs found
Pseudoscalar Vertex, Goldstone Boson and Quark Masses on the Lattice
We analyse the Structure Function collaboration data on the quark
pseudoscalar vertex and extract the Goldstone boson pole contribution, in 1/p2.
The strength of the pole is found to be quite large at presently accessible
scales. We draw the important consequences of this finding for the various
definitions of quark masses, and point out potential problems with the operator
product expansion.Comment: 13 pages, 6 eps figures, LaTeX. Minor modifications to the text, and
corrections to Fig.
Glueball Interpretation of (2230)
On the basis of the results of
and , measured by the BES Collaboration in radiative J/ decays,
combined with the upper limit of Br()Br(), measured by PS185 experiment, we argue
that the distinctive properties of (2230), the flavor-symmetric decays and
the narrow partial decay widths to and as well as its
copious production in radiative J/ decay, would strongly favor the
glueball interpretation of (2230).Comment: Latex file, no figure
A note on possible interpretations for the observed by SELEX
We suggest some possible interpretations for the observed by
SELEX. The could be the first radial excitation of the
ground state (2112), and its unusual decay patten might be
hopefully explained by the node structure of the wave functions. In addition,
the could also be a hybrid state or a
(diquark-antidiquark) bound state.Comment: final version to appear in Phys. Lett. B, references adde
Vacuum replicas in QCD
The properties of the vacuum are addressed in the two- and four-dimensional
quark models for QCD. It is demonstrated that the two-dimensional QCD ('t Hooft
model) possesses only one possible vacuum state - the solution to the mass-gap
equation, which provides spontaneous breaking of the chiral symmetry (SBCS). On
the contrary, the four-dimensional theory with confinement modeled by the
linear potential supplied by the Coulomb OGE interaction, not only has the
chirally-noninvariant ground vacuum state, but it possesses an excited vacuum
replica, which also exhibits SBCS and can realize as a metastable intermediate
state of hadronic systems. We discuss the influence of the latter on physical
observables as well as on the possibility to probe the vacuum background fields
in QCD.Comment: RevTeX4, 26 pages, 8 EPS figures, extended references, corrected some
typos, to appear in Phys.Rev.
O.P.E. and Power Corrections to the QCD coupling constant
Lattice data seems to show that power corrections should be convoked to
describe appropriately the transition of the QCD coupling constant running from
U.V. to I.R. domains. Those power corrections for the Landau-gauge MOM coupling
constant in a pure Yang-Mills theory (N_f=0) are analysed in terms of Operator
Product Expansion (O.P.E.) of two- and three-point Green functions, the gluon
condensate emerging from this study. The semi-classical picture given by
instantons can be also used to look for into the nature of the power
corrections and gluon condensate.Comment: 5 pages, talk given at XXX International Meeting on Fundamental
Physics, Jaca 200
Bound state equation in the Wilson loop approach with minimal surfaces
The large-distance dynamics in quarkonium systems is investigated, in the
large N limit, through the saturation of Wilson loop averages by minimal
surfaces. Using a representation for the quark propagator in the presence of
the external gluon field based on the use of path-ordered phase factors, a
covariant three-dimensional bound state equation of the Breit-Salpeter type is
derived, in which the interaction potentials are provided by the
energy-momentum vector of the straight segment joining the quark to the
antiquark and carrying a constant linear energy density, equal to the string
tension. The interaction potentials are confining and reduce to the linear
vector potential in the static case and receive, for moving quarks,
contributions from the moments of inertia of the straight segment. The
self-energy parts of the quark propagators induce spontaneous breakdown of
chiral symmetry with a mechanism identical to that of the exchange of one
Coulomb-gluon. The nonrelativistic and ultrarelativistic properties of the
bound state spectrum are studied.Comment: 57 pages, 7 figure
Understanding the nature of and through nonleptonic B Decays
We consider the nonleptonic B decays and , involving the newly discovered and the
states. We find that experiments indicate disagreement with model
calculations of their properties and/or breakdown of the factorization
assumption for these decays . We point out that decays involving mesons
where the resonances can be produced via the weak decay of the quark
can provide further information about the nature of these newly discovered
states. We also propose a model to calculate the two body nonleptonic decays , if the and are
interpreted as and molecules.Comment: 14 pages LaTeX; additional reference, notational corrections and
minor clarifications of tex
Coulomb Gauge QCD, Confinement, and the Constituent Representation
Quark confinement and the genesis of the constituent quark model are examined
in nonperturbative QCD in Coulomb gauge. We employ a self-consistent method to
construct a quasiparticle basis and to determine the quasiparticle interaction.
The results agree remarkably well with lattice computations. They also
illustrate the mechanism by which confinement and constituent quarks emerge,
provide support for the Gribov-Zwanziger confinement scenario, clarify several
perplexing issues in the constituent quark model, and permit the construction
of an improved model of low energy QCD.Comment: 43 pages, 14 figures, revtex, uses psfig.st
Consistent OPE Description of Gluon Two- and Three-point Green Function?
We perform an OPE analysis of the flavorless non-perturbative gluon
propagator and the symmetric three-gluon vertex in the Landau gauge. The first
subdominant operator is which can condensate in the Landau gauge
``vacuum'' although being a non-gauge invariant operator. We neglect all higher
dimension operators. Then the gluon propagator and the symmetric three gluon
vertex only depend on one common unknown condensate. We propose a consistency
check from lattice data. At two loops for the leading coefficient and with
corrections at tree-level order the two fitted values for the
condensate do not agree. At three loops we argue that the today unknown
should be equal to to fulfill the OPE relation. Inclusion of the power
corrections' anomalous dimensions should improve further the agreement. We show
that these techniques cannot be applied to the asymmetric three gluon vertex
with one vanishing momentum.Comment: latex-file,10 figs.,13 pg
Estimation of the large order behavior of the plaquette
The universality of vacuum condensate can be exploited to relate the infrared
renormalon caused large order behaviors of different processes. As an
application the normalization constant of the large order behavior of the
average plaquette is estimated using the Adler function.Comment: 7 pages. version published in Phys. Lett.
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