311 research outputs found
Heavy Meson Description with a Screened Potential
We perform a quark model calculation of the and spectra
from a screened funnel potential form suggested by unquenched lattice
calculations. A connection between the lattice screening parameter and an
effective gluon mass directly derived from QCD is established. Spin-spin energy
splittings, leptonic widths and radiative decays are also examined providing a
test for the description of the states.Comment: 17 pages, no figures, to appear in Phys. Rev.
Understanding the and with Sum Rules in HQET
In the framework of heavy quark effective theory we use QCD sum rules to
calculate the masses of the and excited
states. The results are consistent with that the states and
observed by BABAR and CLEO are the and states in the
doublet
Study of decays
We investigate the production of the novel -wave mesons and
, identified as and , in heavy
meson decays, respectively. With the heavy quark limit, we give our modelling
wave functions for the scalar meson . Based on the assumptions of
color transparency and factorization theorem, we estimate the branching ratios
of decays in terms of the obtained wave functions. Some
remarks on productions are also presented.Comment: 16 pages, 2 figures, Revtex4, to be published in Phys. Rev.
Hadronic B Decays Involving Even Parity Charmed Mesons
Hadronic B decays containing an parity-even charmed meson in the final state
are studied. Specifically we focus on the Cabibbo-allowed decays and , where denotes generically a p-wave charmed meson.
The transition form factors are studied in the improved version
of the Isgur-Scora-Grinstein-Wise quark model. We apply heavy quark effective
theory and chiral symmetry to study the strong decays of p-wave charmed mesons
and determine the magnitude of the mixing angle. Except
the decay to the predictions for agree
with experiment. The sign of mixing angle is found to be
positive in order to avoid a severe suppression on the production of
. The interference between color-allowed and color-suppressed
tree amplitudes is expected to be destructive in the decay . Hence, an observation of the ratio
can be used to test the relative signs of
various form factors as implied by heavy quark symmetry. Although the predicted
at the level of exceeds the
present upper limit, it leads to the ratio
as expected from the factorization
approach and from the ratio . Therefore, it is
crucial to have a measurement of this mode to test the factorization
hypothesis. For decays, it is expected that \bar
D_{s0}^*D\gsim \bar D_{s1}D as the decay constants of the multiplet
become the same in the heavy quark limit.Comment: 27 pages, Belle's new data on DD_s^{**} productions in B decays and
on the radiative decay D_{s1}-> D_s\gamma are updated and discussed. Add two
reference
Ethnic differences translate to inadequacy of high-risk screening for gestational diabetes mellitus in an Asian population: a cohort study
Background: universal and high-risk screening for gestational diabetes mellitus (GDM) has been widely studied and debated. Few studies have assessed GDM screening in Asian populations and even fewer have compared Asian ethnic groups in a single multi-ethnic population.Methods: 1136 pregnant women (56.7% Chinese, 25.5% Malay and 17.8% Indian) from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort study were screened for GDM by 75-g oral glucose tolerance test (OGTT) at 26–28 weeks of gestation. GDM was defined using the World Health Organization (WHO) criteria. High-risk screening is based on the guidelines of the UK National Institute for Health and Clinical Excellence.Results: universal screening detected significantly more cases than high-risk screening [crude OR 2.2 (95% CI 1.7-2.8)], particularly for Chinese women [crude OR = 3.5 (95% CI 2.5-5.0)]. Pre-pregnancy BMI > 30 kg/m2 (adjusted OR = 3.4, 95% CI 1.5-7.9) and previous GDM history (adjusted OR = 6.6, 95% CI 1.2-37.3) were associated with increased risk of GDM in Malay women while GDM history was the only significant risk factor for GDM in Chinese women (adjusted OR = 4.7, 95% CI 2.0-11.0).Conclusion: risk factors used in high-risk screening do not sufficiently predict GDM risk and failed to detect half the GDM cases in Asian women. Asian women, particularly Chinese, should be screened to avoid under-diagnosis of GDM and thereby optimize maternal and fetal outcome
Spin Effects in Two Quark System and Mixed States
Based on the numeric solution of a system of coupled channels for vector
mesons (- and -waves mixing) and for tensor mesons (- and -waves
mixing) mass spectrum and wave functions of a family of vector mesons
in triplet states are obtained. The calculations are performed using
a well known Cornell potential with a mixed Lorentz-structure of the
confinement term. The spin-dependent part of the potential is taken from the
Breit-Fermi approach. The effect of singular terms of potential is considered
in the framework of the perturbation theory and by a configuration interaction
approach (CIA), modified for a system of coupled equations. It is shown that
even a small contribution of the -wave to be very important at the
calculation of certain characteristics of the meson states.Comment: 12 pages, LaTe
Production of singlet P-wave and states
No spin-singlet quarkonium state has yet been observed. In this
paper we discuss the production of the singlet P-wave and
states and . We consider two possibilities. In the first the
states are produced via the electromagnetic cascades \ups(3S) \to
\eta_b(2S) + \gamma \to h_b + \gamma \gamma \to \eta_b +\gamma\gamma\gamma
and . A more promising process consists of single pion
transition to the state followed by the radiative transition to the
state: \ups(3S)\to h_b + \pi^0 \to \eta_b + \pi^0 +\gamma and . For a million \ups(3S) or
's produced we expect these processes to produce several hundred events.Comment: 13 pages, LaTeX, 1 figure, to be published Phys. Rev. D. Some
equation numbers and one table number correcte
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
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
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