337 research outputs found
Charm Production in Deep-Inelastic Scattering To Next-To-Leading Order in QCD
We discuss the calculation of to next-to-leading
order (NLO) in QCD, including contributions from both hadronlike and pointlike
photons. We show that the former dominates strongly below , and
the latter above this value. This fact makes for calculable, whereas for it serves to constrain the
small- gluon density in the photon. Both ranges in are accessible at
LEP2. Theoretical uncertainties are well under control. We present rates for
single-tag events for the process for for LEP2.
Although these event rates are small, we believe a measurement of
is feasible.Comment: 7 pages Latex, with 2 eps figs., uuencode
The Small-x Evolution of Unpolarized and Polarized Structure Functions
A brief overview is presented of recent developments concerning resummed
small-x evolution, based upon the renormalization group equation. The
non-singlet and singlet structure functions are discussed for both polarized
and unpolarized deep-inelastic scattering. Quantitative results are displayed
and uncertainties from uncalculated subleading terms are discussed.Comment: 9 pages with 5 EPS figures. To appear in Acta Physica Polonic
Reduced or modified dietary fat for preventing cardiovascular disease
BACKGROUND: Reduction or modification of dietary fat can improve total cholesterol levels, but may also have a variety of effects, both positive and negative, on other cardiovascular risk factors. OBJECTIVES: The aim of this systematic review was to assess the effect of reduction or modification of dietary fats on total and cardiovascular mortality and cardiovascular morbidity over at least 6 months, using all available randomized clinical trials. SEARCH STRATEGY: The Cochrane Library, MEDLINE, EMBASE, CAB Abstracts, CVRCT registry and related Cochrane Groups' trial registers were searched through spring 1998, SIGLE to January 1999. Trials known to experts in the field and biographies were included through May 1999. SELECTION CRITERIA: Trials fulfilled the following criteria: 1) randomized with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) healthy adult humans, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available. Inclusion decisions were duplicated, disagreement resolved by discussion or a third party. DATA COLLECTION AND ANALYSIS: Rate data were extracted by two independent reviewers and meta-analysis performed using random effects methodology. Meta-regression and funnel plots were used. MAIN RESULTS: Twenty seven studies were included (40 intervention arms, 30,901 person-years). There was no significant effect on total mortality (rate ratio 0.98, 95% CI 0.86 to 1.12), a trend towards protection form cardiovascular mortality (rate ratio 0.91, 95% CI 0.77 to 1.07), and significant protection from cardiovascular events (rate ratio 0.84, 95% CI 0.72 to 0.99). The latter became non-significant on sensitivity analysis. Trials where participants were involved for more than 2 years showed significant reductions in the rate of cardiovascular events and a suggestion of protection from total mortality. The degree of protection from cardiovascular events appeared similar in high and low risk groups, but was statistically significant only in the former. REVIEWER'S CONCLUSIONS: The findings are suggestive of a small but potentially important reduction in cardiovascular risk in trials longer than two years. Lifestyle advice to all those at high risk of cardiovascular disease (especially where statins are unavailable or rationed), and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates
Theoretical Uncertainties in the QCD Evolution of Structure Functions and their Impact on
The differences are discussed between various next-to-leading order
prescriptions for the QCD evolution of parton densities and structure
functions. Their quantitative impact is understood to an accuracy of 0.02\%.
The uncertainties due to the freedom to choose the renormalization and
factorization scales are studied. The quantitative consequences of the
different uncertainties on the extraction of the strong coupling constant
from scaling violations in deep--inelastic scattering are estimated
for the kinematic regime accessible at HERA.Comment: 10 pages Latex, including 3 eps-figures, and a style file. To appear
in: Proc. of the International Workshop: QCD and QED in Higher Orders,
Rheinsberg, April, 1996, Nucl. Phys. {\bf B} (Proc. Suppl); The lay-out of
the paper has been changed, one figure sent separately before has been bound
i
On the Resummation of the epe^+e^-$ Annihilation
The resummation of the non-singlet contributions is
performed for initial state QED corrections. As examples, the effect of the
resummation on neutral-current deep-inelastic scattering and the scattering cross section near the -peak is
investigated.Comment: 11 pages Latex, including 3 eps-figure
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