875 research outputs found
Predicative Ability of QCD Sum Rules for Decuplet Baryons
QCD sum rules for decuplet baryon two-point functions are investigated using
a comprehensive Monte-Carlo based procedure. In this procedure, all
uncertainties in the QCD input parameters are incorporated simultaneously,
resulting in realistic estimates of the uncertainties in the extracted
phenomenological parameters. Correlations between the QCD input parameters and
the phenomenological parameters are studied by way of scatter plots. The
predicted couplings are useful in evaluating matrix elements of decuplet
baryons in the QCD sum rule approach. They are also used to check a cubic
scaling law between baryon couplings and masses, as recently found by Dey and
coworkers. The results show a significant reduction in the scaling constant and
some possible deviations from the cubic law.Comment: 13 pages, RevTeX, 5 PS figures embedded with psfig.st
B0 - anti-B0 mixing beyond factorization
We present a calculation of the B0 - anti-B0 mixing matrix element in the
framework of QCD sum rules for three-point functions. We compute alpha_s
corrections to a three-point function at the three-loop level in QCD
perturbation theory, which allows one to extract the matrix element with
next-to-leading order (NLO) accuracy. This calculation is imperative for a
consistent evaluation of experimentally-measured mixing parameters since the
coefficient functions of the effective Hamiltonian for B0 - anti-B0 mixing are
known at NLO. We find that radiative corrections violate factorization at NLO;
this violation is under full control and amounts to 10%.Comment: 4 pages, 3 figures, LaTeX2
Critical Behavior of J/psi across the Phase Transition from QCD sum rules
We study behavior of J/psi in hot gluonic matter using
QCD sum rules. Taking into account temperature dependences of the gluon
condensates extracted from lattice thermodynamics for the pure SU(3) system, we
find that the mass and width of J/psi exhibit rapid change across the critical
temperature.Comment: 5 pages, 3 figures. Poster contribution for Quark Matter 2008. To be
published in the proceeding
Isospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules
We use QCD sum rules for the three point function of a pseudoscalar and two
nucleonic currents in order to estimate the charge dependence of the pion
nucleon coupling constant coming from isospin violation in the
strong interaction. The effect can be attributed primarily to the difference of
the quark condensates . For the splitting
we obtain an interval of to , the uncertainties coming mainly from the input
parameters. The charged pion nucleon coupling is found to be the average of
and . Electromagnetic effects are not included.Comment: 18 pages (REVTeX) + 2 figures (as PostScript), to be published in
PRC, replaced with final version: inclusion of pi-eta mixing and N -> N*
transition
The Psychobiology of Authentic and Simulated Dissociative Personality States:The Full Monty
The etiology of dissociative identity disorder (DID) remains a topic of debate. Proponents of the fantasy model and the trauma model of DID have both called for more empirical research. To this end, the current study presents new and extended data analyses of a previously published (H2O)-O-15 positron emission tomography imaging study. This study included 29 subjects: 11 patients with DID and 10 high- and 8 low-fantasy-prone DID-simulating mentally healthy control subjects. All subjects underwent an autobiographical memory script-driven (neutral and trauma related) imagery paradigm in 2 (simulated) dissociative personality states (neutral and trauma related). Psychobiological and psychophysiological data were obtained. Results of the new post-hoc tests on the psychophysiological responses support the trauma model. New results of the brain imaging data did not support the fantasy model. This study extends previously published results by offering important new supporting data for the trauma model of DID.</p
Octet Baryons at Finite Temperature: QCD Sum Rules vs. Chiral Symmetry
Correlators of the octet baryons in the hot pion gas are studied in the
framework of the QCD sum rule. The condensates appearing in the OPE side of the
correlators become T-dependent through the interaction with thermal pions. We
present an explicit demonstration that the -dependence of the
condensates is completely compensated by the change of the pole residue and the
scattering effect in the spectral functions. Therefore
the baryon masses are constant to this order, although
, which
is consistent with the chiral symmetry constraint by Leutwyler and Smilga.Comment: 19 pages, MSUNSCL-870, LaTex files, 2 figs. consisting of simple
Feynmann diagrams not included, Phys.Rev.D in pres
Light-Quark Mesons and Four-Quark Condensates at Finite Temperature
We propose an analog of the familiar gap equation for the case of four-quark
condensates at finite temperature. The condensates of interest correspond to
scalar, vector, psudoscalar, axial vector, and tensor Dirac structures. Working
with correlators at zero chemical potential without factorization, we arrive at
coupled equations for these four-quark condensates and the masses of certain
light-quark mesons. We study the temperature dependence of the four-quark
condensates and masses; in one of our models, factorization of the four-quark
condensates is shown to be increasingly violated as the temperature is
increased toward . The 2 tensor mesons a(1320)-f(1270) are
identified as especially sensitive probes of the four-quark condensates.Comment: Latex file, 6 Fig
QCD sum rules for the pseudoscalar decay constants - To constrain the strange quark mass
We study the higher order corrections of quark masses to the
Gell-MannOakesRenner (GOR) relation by constructing QCD sum rules
exclusively for pseudoscalar mesons from the axial-vector correlation function,
. To project out
the pseudoscalar meson contributions, we apply to this
correlation function and construct sum rules for the decay constants of
pseudoscalar mesons, and . The OPE is proportional to
quark masses due to PCAC. To leading order in quark mass, each sum rule
reproduces the corresponding GOR relation. For kaon and , the deviation
from the GOR relation due to higher orders in quark mass is found to be
substantial. But the deviation gives better agreements with the phenomenology.
Our sum rule provides a sensitive relation between and , which
stringently constrain the value for . To reproduce the experimental value
for , is found to be 186 MeV at 1 GeV scale. The sum
rule also supports this finding.Comment: 14 pages including 3 figures. slightly revised. Accepted for
publication in Physical Review
On the asymptotic behavior of the electroweak gauge bosons vacuum polarization functions for arbitrary quark masses
We derive the QCD corrections to the electroweak gauge bosons vacuum
polarization functions at high and zero--momentum transfer in the case of
arbitrary internal quark masses. We then discuss in this general case (i) the
connection between the calculations of the vector bosons
self--energies using dimensional regularization and the one performed via a
dispersive approach and (ii) the QCD corrections to the parameter for a
heavy quark isodoublet.Comment: 14 pages + 2 figures (not included: available by mail from A.
Djouadi), Preprint UdeM-LPN-TH-93-156 and NYU-TH-93/05/0
Contribution of higher meson resonances to the electromagnetic -meson mass difference
Modifications of the DGMLY relation for calculation of electromagnetic
-meson mass difference based on the Chiral Symmetry Restoration phenomenon
at high energies as well as the Operator Product Expansion of quark densities
for vector () and axial-vector () meson fields difference are
proposed. In the calculations higher meson resonances in vector and
axial-vector channels are taken into account. It is shown that the inclusion of
the first and radial excitations improves the results for
electromagnetic -meson mass difference as compared with the previous ones.
Estimations on the electromagnetic and -meson decay constants and
the constant of effective chiral Lagrangian are obtained from the
generalized Weinberg sum rules.Comment: Latex2e, 10 pages, submitted to Yad. Phy
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