34 research outputs found
Supersymmetric effects in top quark decay into polarized W-boson
We investigate the one-loop supersymmetric QCD (SUSY-QCD) and electroweak
(SUSY-EW) corrections to the top quark decay into a b-quark and a longitudinal
or transverse W-boson. The corrections are presented in terms of the
longitudinal ratio \Gamma(t-->W_L b)/\Gamma(t--> W b) and the transverse ratio
\Gamma(t-->W_- b)/\Gamma(t--> W b). In most of the parameter space, both
SUSY-QCD and SUSY-EW corrections to these ratios are found to be less than 1%
in magnitude and they tend to have opposite signs. The corrections to the total
width \Gamma(t-->W b) are also presented for comparison with the existing
results in the literature. We find that our SUSY-EW corrections to the total
width differ significantly from previous studies: the previous studies give a
large correction of more than 10% in magnitude for a large part of the
parameter space while our results reach only few percent at most.Comment: Version in PRD (explanation and refs added
Flavor Changing processes in Quarkonium Decays
We study flavor changing processes and in the B factories and the Tau-Charm factories. In the
standard model, these processes are predicted to be unobservable, so they serve
as a probe of the new physics. We first perform a model independent analysis,
then examine the predictions of models; such as TopColor models, MSSM with
R-parity violation and the two Higgs doublet model; for the branching ratios of
and . We find that
these branching ratios could be as large as and in the
presence of new physics.Comment: Minor changes in the last section. Latex 22 pages, one figure. To
appear in Phys. Rev.
Scale setting for alpha_s beyond leading order
We present a general procedure for incorporating higher-order information
into the scale-setting prescription of Brodsky, Lepage and Mackenzie. In
particular, we show how to apply this prescription when the leading coefficient
or coefficients in a series in the strong coupling alpha_s are anomalously
small and the original prescription can give an unphysical scale. We give a
general method for computing an optimum scale numerically, within dimensional
regularization, and in cases when the coefficients of a series are known. We
apply it to the heavy quark mass and energy renormalization in lattice NRQCD,
and to a variety of known series. Among the latter, we find significant
corrections to the scales for the ratio of e+e- to hadrons over muons, the
ratio of the quark pole to MSbar mass, the semi-leptonic B-meson decay width,
and the top decay width. Scales for the latter two decay widths, expressed in
terms of MSbar masses, increase by factors of five and thirteen, respectively,
substantially reducing the size of radiative corrections.Comment: 39 pages, 15 figures, 5 tables, LaTeX2
Two-Loop O(alpha_s G_F M_Q^2) Heavy-Quark Corrections to the Interactions between Higgs and Intermediate Bosons
By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the
shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual
high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark.
Invoking the improved Born approximation, we then find the corresponding
corrections to various four- and five-point Higgs-boson production and decay
processes which involve the W^+W^-H and ZZH vertices with one or both of the
gauge bosons being connected to light-fermion currents, respectively. This
includes e^+e^- -> f anti-f H via Higgs-strahlung, via W^+W^- fusion (with f =
nu_e), and via ZZ fusion (with f = e), as well as H -> 2V -> 4f (with V = W,
Z).Comment: 20 pages (Latex); Physical Review D (to appear
The Changing Face of European Ports as a Result of their evolving Use since the Nineteenth Century
The aim of this article is to make a comparative study of the history of European ports during the last two centuries showing their complexity and specific characteristics. Whereas during the process of waterfront development, local governments emphasize the relationship of ports with sailing ships as a marketing instrument, the industrial history of those ports are mostly neglected. This article focuses on the industrial port, showing differences in the chronology of construction and in their urban impact. Hinterland and inland transportation were responsible for a part of those differences, as well as geographical and political circumstances. However, social aspects as well as technological issues showed comparable evolutions. The decline of the industrial port city is a part of the general process of de-industrialization of Europe, but it has its own specific features. At least it is clear that the development of port cities during the last two centuries is far more complex than some stage theories about port development assume