1,020 research outputs found
Fundamental groups of open K3 surfaces, Enriques surfaces and Fano 3-folds
We investigate when the fundamental group of the smooth part of a K3 surface
or Enriques surface with Du Val singularities, is finite. As a corollary we
give an effective upper bound for the order of the fundamental group of the
smooth part of a certain Fano 3-fold. This result supports Conjecture A below,
while Conjecture A (or alternatively the rational connectedness conjecture in
[KoMiMo] which is still open when the dimension is at least 4) would imply that
every log terminal Fano variety has a finite fundamental group (now a Theorem
of S. Takayama).Comment: Journal of Pure and Applied Algebra, to appear; 24 page
Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays
When studying B decays within the Standard Model, it is customary to use the
unitarity of the CKM matrix in order to write the decay amplitudes in terms of
only two of the three weak phases which appear in the various diagrams.
Occasionally, it is mentioned that those two weak phases can be used in order
to describe any decay amplitude, even beyond the Standard Model. Here we point
out that, when describing a generic decay amplitude, the two weak phases can be
chosen completely at will, and we study the behavior of the decay amplitudes
under changes in the two weak phases chosen as a basis. Of course, physical
observables cannot depend on such reparametrizations. This has an impact in
discussions of the SM and in attempts to parametrize new physics effects in the
decay amplitudes. We illustrate these issues by looking at B --> psi K_S and
the isospin analysis in B --> pi pi.Comment: 16 pages, RevTe
Study of pure annihilation type decays
In this work, we calculate the rare decays and in perturbative QCD approach with Sudakov resummation.
We give the branching ratio of for , which will
be tested soon in factories.
The decay has a very small branching ratio at
, due to the suppression from CKM matrix elements . It may be sensitive to new physics contributions.Comment: 14 pages, 1 figur
Perturbative QCD analysis of decays
We study the first observed charmless modes, the
decays, in perturbative QCD formalism. The obtained branching ratios
are larger than
from QCD factorization. The comparison of the predicted magnitudes and phases
of the different helicity amplitudes, and branching ratios with experimental
data can test the power counting rules, the evaluation of annihilation
contributions, and the mechanism of dynamical penguin enhancement in
perturbative QCD, respectively.Comment: 14 pages, 2 tables, brief disscussion on hard sacle added, version to
appear in PR
Supersymmetric contributions to direct CP violation in K -> pi pi gamma decays
We analyze the supersymmetric contributions to direct-CP-violating
observables in decays induced by gluino-mediated
magnetic-penguin operators. We find that \epsp_{+-\gamma} and the
differential width asymmetry of decays could
be substantially enhanced with respect to their Standard Model values,
especially in the scenario where \epsp/\eps is dominated by supersymmetric
contributions. These observables could therefore provide a useful tool to
search for New Physics effects in transitions, complementary to
\epsp/\eps and rare decays.Comment: 14 pages, Latex. Numerical error in Eq.(36) corrected, conclusions
unchanged; version to appear in Phys. Lett.
B meson light-cone wavefunctions in the heavy quark limit
We present a systematic study of the B meson light-cone wavefunctions in QCD
in the heavy-quark limit. We construct model-independent formulae for the
light-cone wavefunctions in terms of independent dynamical degrees of freedom,
which exactly satisfy the QCD equations of motion and constraints from
heavy-quark symmetry. The results demonstrate novel behaviors of longitudinal
as well as transverse momentum distribution in the B mesons.Comment: 5 pages LaTeX, 1 style file. Talk presented at RADCOR/Loops and Legs
2002, Kloster Banz, Germany, September 8-13, 200
Molecular mechanisms underlying anti-tumor promoting activities of heat-processed Panax ginseng C.A. Meyer.
Recently, there have been considerable efforts to search for naturally occurring substances that can inhibit, reverse, or retard the multi-stage carcinogenesis. A wide array of phenolic substances derived from edible and medicinal plants have been reported to possess anticarcinogenic and antimutagenic activities and in many cases, the chemopreventive activities of phytochemicals are associated with their anti-inflammatory and/or antioxidative properties. Panax ginseng C.A. Meyer cultivated in Korea has been widely used in traditional herbal medicine for the treatment of various diseases. Certain fractions or purified ingredients of ginseng have been shown to exert anticarcinogenic and antimutagenic activities. Our previous studies have revealed that the methanol extract of heat-processed Panax ginseng C.A. Meyer attenuates the lipid peroxidation in rat brain homogenates and is also capable of scavenging superoxide generated by xanthine- xanthine oxidase or by 12-O-tetradecanoylphorbol-13-acetate (TPA) in differentiated human promyelocytic leukemia (HL-60) cells. Topical application of the same extract onto shaven backs of female ICR mice also suppressed TPA-induced skin tumor promotion. Likewise, topical application of ginsenoside Rg3, one of the constituents of heat-treated ginseng, significantly inhibited TPA-induced mouse epidermal ornithine decarboxylase activity and skin tumor promotion. Expression of cyclooxygenase-2 (COX-2) in TPA-stimulated mouse skin was markedly suppressed by Rg3 pretreatment. In addition, Rg3 inhibited TPA-stimulated activation of NF-kappaB and extracellular-regulated protein kinase (ERK), one of the mitogen-activated protein (MAP) kinase in mouse skin and also in cultured human breast epithelial cells (MCF-10A)
CP asymmetry, branching ratios and isospin breaking effects of B -> K* gamma with the perturbative QCD approach
The radiative B -> K* gamma mode is caused by a penguin operator which is a
quantum correction. Thus this mode may be useful in the search for physics
beyond the standard model. In this paper, we compute the branching ratio,
direct CP asymmetry, and isospin breaking effects within the Standard Model in
the framework perturbative QCD, and discuss how new physics might show up in
this decay.Comment: 20 pages, 44 figure
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