314 research outputs found
Analyticity Properties and Unitarity Constraints of Heavy Meson Form Factors
We derive new bounds on the b-number form factor of the B meson.
(Revised version of hep-ph/9306214).Comment: 22 page
Model-Independent Semileptonic Form Factors Using Dispersion Relations
We present a method for parametrizing heavy meson semileptonic form factors
using dispersion relations, and from it produce a two-parameter description of
the B -> B elastic form factor. We use heavy quark symmetry to relate this
function to B -> D* l nu form factors, and extract
|V_cb|=0.0355^{+0.0029}_{-0.0025} from experimental data with a least squares
fit. Our method eliminates model-dependent uncertainties inherent in choosing a
parametrization for the extrapolation of the differential decay rate to
threshold.Comment: uses lanlmac(harvmac) and epsf, 12 pages, 1 eps figure included (Talk
by BG at the 6-th International Symposium on Heavy Flavour Physics, Pisa,
Italy, 6--10 June, 1995
Chiral Dynamics and Heavy Quark Symmetry in a Toy Field Theoretic Model
We study a solvable QCD--like toy theory, a generalization of the
Nambu--Jona-Lasinio model, which implements chiral symmetries of light quarks
and heavy quark symmetry. The chiral symmetric and chiral broken phases can be
dynamically tuned. This implies a parity doubled heavy--light meson system,
corresponding to a multiplet and a heavy spin
multiplet. Consequently the mass difference of the two multiplets is given by a
Goldberger--Treiman relation and is found to be small. The Isgur--Wise
function, , the decay constant, , and other observables are
studied.Comment: 42 pages, SSCL-PP-243; Fermi-Pub-93/059-
Simply Modeling Meson HQET
A simple relativistic model of heavy-quark-light-quark mesons is proposed. In
an expansion in inverse powers of the heavy quark mass we find that all zeroth
and first order heavy quark symmetry relations are satisfied. The main results
are: - the difference between the meson mass and the heavy quark mass plays a
significant role even at zeroth order; - the slope of the Isgur-Wise function
at the zero recoil point is typically less than ; - the first order
correction to the pseudoscalar decay constant is large and negative; - the four
universal functions describing the first order corrections to the semileptonic
decay form factors are small; - these latter corrections are quite insensitive
to the choice of model parameters, and in particular to the effects of
hyperfine mass splitting.Comment: 17 pages, LaTeX, 3 LaTeX figures in separate file, UTPT-92-16. This
is the version published long ago but not previously archive
QED Logarithms in the Electroweak Corrections to the Muon Anomalous Magnetic Moment
We employ an effective Lagrangian approach to derive the leading-logarithm
two-loop electroweak contributions to the muon anomalous magnetic moment, a_mu.
We show that these corrections can be obtained using known results on the
anomalous dimensions of composite operators. We confirm the result of Czarnecki
et al. for the bosonic part and present the complete sin^2 \theta_W dependence
of the fermionic contribution. The approach is then used to compute the
leading-logarithm three-loop electroweak contribution to a_mu. Finally we
derive, in a fairly model-independent way, the QED improvement of new-physics
contributions to a_mu and to the electric dipole moment (EDM) of the electron.
We find that the QED corrections reduce the effect of new physics at the
electroweak scale by 6% (for a_mu) and by 11% (for the electron EDM).Comment: 13 page
Updating the Unitarity Triangle: Top Quark Mass Versus Nonperturbative Uncertainties
We summarize the present knowledge on the non-perturbative hadronic inputs
needed in the analysis of - mixing and the CP-violating
parameter of the - system. Using this information,
together with the recently determined value of the top-quark mass, we update
the phenomenological constraints on the unitarity triangle.Comment: 21 pages, Plain LateX, 7 figures included, preprint FTUV/94-37,
IFIC/94-32, NBI-94-3
Form Factors
The bounds on the form factors for decay are
studied. Constrained by lattice data and a constrained conformal mapping, the
more informations can be obtained for form-factor which dominates
the decay rate at large . Specifically, we confirm a moderately increasing
behavior of this form factor.Comment: 15 pages, Latex, 4 figure
Analyticity, Shapes of Semileptonic Form Factors, and B to pi l nu
We give a pedagogical discussion of the physics underlying dispersion
relation-derived parameterizations of form factors describing B -> pi l nu and
B -> D l nu. Moments of the dispersion relations are shown to provide
substantially tighter constraints on the f_+ (t) form factor describing B -> pi
l nu than the unweighted dispersion relation alone. Heavy quark spin symmetry
relations between the B -> pi l nu and B^* -> pi l nu form factors enables such
constraints to be tightened even further.Comment: 18 pages, Latex, three eps figures include
CagA-positive Helicobacter pylori infection is not associated with decreased risk of Barrett's esophagus in a population with high H. pylori infection rate
BACKGROUND & AIM: The role that H. pylori infection plays in the development of and Barrett's esophagus (BE) is uncertain. We tested the hypothesis that infection with cagA+ Helicobacter pylori strains protects against the development of BE. METHODS: We studied 104 consecutive patients, residents in an area with a high prevalence of H. pylori infection, with BE and 213 sex- and age-matched controls. H. pylori infection and CagA antibody status were determined by western blot serology. RESULTS: H. pylori prevalence was higher in patients with BE than in controls (87.5% vs. 74.6%; OR. 2.3; 95% CI: 1.23–4.59). Increasing age was associated with a higher prevalence of H. pylori (p < 0.05). The prevalence of CagA+ H. pylori serology was similar in patients with BE and controls (64.4% vs. 54.5%; NS). Type I H. pylori infection (CagA+ and VacA+) was similar in patients with BE and controls (44.2% vs. 41.3%; NS). Logistic regression analysis identified alcohol (O.R. 7.09; 95% CI 2.23–22.51), and H. pylori infection (OR: 2.41; 95%CI: 1.20–4.84) but not CagA+ serology as independent factors. CONCLUSION: Neither H. pylori infection nor H. pylori infection by CagA+ strains reduce the risk of BE in a population with high prevalence of H. pylori infection
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
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