108,119 research outputs found
Signatures of Supersymmetry in B Decays - A Theoretical Perspective
We discuss precision tests of the standard model in radiative and
semileptonic rare B-decays and CP-violating asymmetries, and possible
signatures of supersymmetry in these processes. Motivated by current data, and
with an eye on the forthcoming measurements, we restrict ourselves to the
processes in which the bench marks set by the standard model have either been
met by ongoing experiments or are expected to be met shortly. This includes the
mixing-induced CP asymmetry, measured through , and branching
ratios for the radiative and semileptonic rare decays , , and ,
where .Comment: 19 pages, 5 figures (requires sprocl.sty and epsf); invited talk, to
be published in the proceedings of the International Conference on Flavor
Physics ICFP2001, Zhang-Jia-Jie City, Peoples Republic of China, May 31 -
June 6, 200
Inequality and the Dynamics of Poverty and Growth
This paper models the dynamic interactions between growth and distribution in the analysis of the behavior of poverty over time. The model permits formal analysis of the factors that led to the growth collapse as well as the rise in poverty in Africa and other developing regions, except Asia, during 1975-96 period. Using indicators of average country performance during this period-- in terms of the rate of acceleration of growth, changes in poverty and extent of inequality—the model suggests tentative strategies for dealing with poverty. The main policy recommendation of this analysis is that, for the majority of countries—36 out of 47—any serious strategy for poverty reduction must include both policies for accelerating growth as well as measures for effecting more equitable income distribution. Moreover, the latter must be sufficiently deep either to shake-off the "transitional", though lingering, "low equilibrium trap" that characterizes some economies; or to more others from the "bad" equilibrium of stationary, but high, poverty.
Improved -Meson Distribution Amplitudes from Inclusive Decay
We calculate the -meson energy spectrum in the decay in the leading-order
perturbative QCD in the static-quark limit for the orthoquarkonium.Our
principal result is the extraction of parameters of the
effective vertex function (EVF) involving a virtual and a real gluon from the
available data on the hard part of the -meson energy spectrum. The
perturbative-QCD based framework provides a good description of the available
CLEO data, allowing one to constrain the lowest Gegenbauer coefficients
and of the quark-antiquark and gluonic distribution
amplitudes of the -meson. The resulting constraints are combined
with the existing ones on these coefficients from an analysis of the
transition form factor and the requirement of positivity
of the EVF, yielding and for . This reduces significantly
the current uncertainty on these coefficients.Comment: 4 pages, 4 figures, use svjour.cls and svepj.clo; talk given at the
International Europhysics Conference on High-Energy Physics (HEP 2003), 17-23
July 2003, Aachen, Germany. Title change
Branching Ratios for and Decays in Next-to-Leading Order in the Large Eneregy Effective Theory
We calculate the so-called hard spectator corrections in in the leading-twist approximation to the decay widths for and decays and their charge conjugates, using
the Large Energy Effective Theory (LEET) techniques. Combined with the hard
vertex and annihilation contributions, they are used to compute the branching
ratios for these decays in the next-to-leading order (NLO) in the strong
coupling and in leading power in . These
corrections are found to be large, leading to the inference that the
theoretical branching ratios for the decays in the LEET
approach can be reconciled with current data only for significantly lower
values of the form factors than their estimates in the QCD sum rule and Lattice
QCD approaches. However, the form factor related uncertainties mostly cancel in
the ratios and , where , and hence their
measurements will provide quantitative information on the standard model
parameters, in particular the ratio of the CKM matrix elements and the inner angle of the CKM-unitarity triangle. We
also calculate direct CP asymmetries for the decays
and and find, in conformity with the
observations made in the existing literature, that the hard spectator
contributions significantly reduce the asymmetries arising from the vertex
corrections.Comment: 45 pages, 18 figures (requires amssymb and epsf); replaced with the
revised versio
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