575 research outputs found
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
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)
A Detailed Analysis of One-loop Neutrino Masses from the Generic Supersymmetric Standard Model
In the generic supersymmetric standard model which had no global symmetry
enforced by hand, lepton number violation is a natural consequence.
Supersymmetry, hence, can be considered the source of experimentally demanded
beyond standard model properties for the neutrinos. With an efficient
formulation of the model, we perform a comprehensive detailed analysis of all
one-loop contributions to neutrino masses.Comment: 27 pages Revtex, no figur
Branching ratios of decays in perturbative QCD approach
We study the rare decays , which can occur only via
annihilation type diagrams in the standard model. We calculate all of the four
modes, , in the framework of perturbative QCD approach
and give the branching ratios of the order about .Comment: 18 pages, 1 figure, Revte
Possible Large Direct CP Violations in Charmless B-Decays
We discuss the perturbative QCD approach for the exclusive two body B-meson
decays to light mesons. We briefly review its ingredients and some important
theoretical issues on factorization approach. We show numerical results which
are compatible with present experimantal data for the charmless B-meson decays.
Specailly we predict the possibility of large direct CP violation effects in
and .
In the last section we investigate two methods to determine the weak phases
and from processes. We obtain bounds on
and from present experimental measurements.Comment: 18 pages, latex, 8 figures and 8 tables, typos corrected and added
more tables and references. Presented at the 3rd workshop on Higher
Luminosity B Factory, 6-7 August 2002, Kanagawa, Japan; Submitted to Phys.
Rev.
QCD factorization for B -> PP
In this work, we give a detailed discussion for QCD factorization involved
the complete chirally enhanced power corrections for B decays to two light
pseudoscalar mesons, and present some detailed calculations of radiative
corrections at the order of alpha_s. We point out that the infrared finiteness
of the vertex corrections in the chirally enhanced power corrections requires
twist-3 light-cone distribution amplitudes (LCDAs) of the light pseudoscalar
symmetric. However, even in the symmetric condition, there is also logarithmic
divergence from the endpoints of the twist-3 LCDAs in the hard spectator
scattering. We point out that the decay amplitudes of B --> PP predicted by QCD
factorization are really free of the renormalization scale dependence, at least
at the order of alpha_s. At last, we briefly compare the QCD factorization with
the generalized factorization and PQCD method.Comment: 31 pages, 3 eps figure
One-loop Neutron Electric Dipole Moment from Supersymmetry without R-parity
We present a detailed analysis together with exact numerical calculations on
one-loop contributions to neutron electric dipole moment from supersymmetry
without R-parity, focusing on the gluino, chargino, and neutralino
contributions. Apart from the neglected family mixing among quarks, complete
formulae are given for the various contributions, through the quark dipole
operators, to which the present study is restricted. We discuss the structure
and main features of the R-parity violating contributions and the interplay
between the R-parity conserving and violating parameters. In particular, the
parameter combination , under the optimal
parametrization adopted, is shown to be solely responsible for the R-parity
violating contributions in the supersymmetric loop diagrams. While
could bear a complex phase, the latter is not
necessary to have a R-parity violating contribution.Comment: 43 pages Revtex with 15 eps- and 4 ps- figure files incoporated;
proofread version to be published in Phys. Rev.
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