46 research outputs found
Generating Functional for Strong and Nonleptonic Weak Interactions
The generating functional for Green functions of quark currents is given in
closed form to next-to-leading order in the low-energy expansion for chiral
SU(3), including one-loop amplitudes with up to three meson propagators. Matrix
elements and form factors for strong and nonleptonic weak processes with at
most six external states can be extracted from this functional by performing
three-dimensional flavour traces. To implement this procedure, a Mathematica
program is provided that evaluates amplitudes with at most six external mesons,
photons (real or virtual) and virtual W (semileptonic form factors). The
program is illustrated with several examples that can be compared with existing
calculations.Comment: 26 pages; references added, comparison with other programs added,
small changes in the text, version to appear in JHE
A toxicogenomic data space for system-level understanding and prediction of EDC-induced toxicity.
Endocrine disrupting compounds (EDCs) are a persistent threat to humans and wildlife due to their ability to interfere with endocrine signaling pathways. Inspired by previous work to improve chemical hazard identification through the use of toxicogenomics data, we developed a genomic-oriented data space for profiling the molecular activity of EDCs in an in silico manner, and for creating predictive models that identify and prioritize EDCs. Predictive models of EDCs, derived from gene expression data from rats (in vivo and in vitro primary hepatocytes) and humans (in vitro primary hepatocytes and HepG2), achieve testing accuracy greater than 90%. Negative test sets indicate that known safer chemicals are not predicted as EDCs. The rat in vivo-based classifiers achieve accuracy greater than 75% when tested for invitro to in vivoextrapolation. This study reveals key metabolic pathways and genes affected by EDCs together with a set of predictive models that utilize these pathways to prioritize EDCs in dose/time dependent manner and to predict EDCevokedmetabolic diseases
CP violating asymmetry in decays
The CP violating asymmetry from the decay rates of
charged Higgs bosons into the lightest neutral Higgs boson and a boson
is calculated and discussed in the complex MSSM. The contributions from all
complex phases are considered, especially from the top-squark trilinear
coupling, which induces a large contribution to the CP asymmetry.Comment: 19 pages, 10 figures, version published in JHE
CP-odd A^0 production at e^+e^- colliders in MSSM with CP violating phases
We study the production of a heavy CP-odd boson in association with a
photon and a Z boson as well as the
single production of via in the MSSM
with CP violating phases. In the case of , we show
that the squark contribution, which vanishes in the MSSM with real parameters,
turns out to be sizeable in presence of CP violating phases in the soft SUSY
parameters. For in both the 2HDM and MSSM
with real parameters, the cross section does not reach observable rates at a
NLC. It is found that with a large CP violating phase for , cross sections
of the order 0.1 fb are attainable for all the processes ,
and .Comment: 12 pages, latex, 7 eps figures. One new figure, new discussion arroud
it. Version to appear in Phys. Rev.
Feynman Rules for the Rational Part of the Standard Model One-loop Amplitudes in the 't Hooft-Veltman Scheme
We study Feynman rules for the rational part of the Standard Model
amplitudes at one-loop level in the 't Hooft-Veltman scheme.
Comparing our results for quantum chromodynamics and electroweak 1-loop
amplitudes with that obtained based on the Kreimer-Korner-Schilcher (KKS)
scheme, we find the latter result can be recovered when our
scheme becomes identical (by setting in our expressions)
with the KKS scheme. As an independent check, we also calculate Feynman rules
obtained in the KKS scheme, finding our results in complete agreement with
formulae presented in the literature. Our results, which are studied in two
different schemes, may be useful for clarifying the
problem in dimensional regularization. They are helpful to eliminate or find
ambiguities arising from different dimensional regularization schemes.Comment: Version published in JHEP, presentation improved, 41 pages, 10
figure
Higgs Boson Masses in the Complex NMSSM at One-Loop Level
The Next-to-Minimal Supersymmetric Extension of the Standard Model (NMSSM)
with a Higgs sector containing five neutral and two charged Higgs bosons allows
for a rich phenomenology. In addition, the plethora of parameters provides many
sources of CP violation. In contrast to the Minimal Supersymmetric Extension,
CP violation in the Higgs sector is already possible at tree-level. For a
reliable understanding and interpretation of the experimental results of the
Higgs boson search, and for a proper distinction of Higgs sectors provided by
the Standard Model or possible extensions, the Higgs boson masses have to be
known as precisely as possible including higher-order corrections. In this
paper we calculate the one-loop corrections to the neutral Higgs boson masses
in the complex NMSSM in a Feynman diagrammatic approach adopting a mixed
renormalization scheme based on on-shell and conditions. We study
various scenarios where we allow for tree-level CP-violating phases in the
Higgs sector and where we also study radiatively induced CP violation due to a
non-vanishing phase of the trilinear coupling in the stop sector. The
effects on the Higgs boson phenomenology are found to be significant. We
furthermore estimate the theoretical error due to unknown higher-order
corrections by both varying the renormalization scheme of the top and bottom
quark masses and by adopting different renormalization scales. The residual
theoretical error can be estimated to about 10%
corrections to production at factories
We investigate the corrections to () in the NRQCD factorization approach. These
next-to-leading order (NLO) corrections are calculated at the level of helicity
amplitude. We have made a detailed analysis for both polarized and unpolarized
cross sections, and compared our predictions with the measurements at the
factories. We also derive the asymptotic expressions for each of the NLO
helicity amplitudes, and confirm the earlier speculation that at NLO in
, the double logarithm of type appearing in the
NRQCD short-distance coefficient is always associated with the
helicity-suppressed channels.Comment: v3, 18+3 pages, 6 figures, 3 tables; some formulas corrected, erratum
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Yang-Mills amplitude relations at loop level from non-adjacent BCFW shifts
This article studies methods to obtain relations for scattering amplitudes at
the loop level, with concrete examples at one loop. These methods originate in
the analysis of large so-called Britto-Cachazo-Feng-Witten shifts of tree level
amplitudes and loop level integrands. In particular BCFW shifts for particles
which are not color adjacent and some particular generalizations of this
situation are analyzed in some detail in four and higher dimensions. For
generic non-adjacent shifts our results are independent of loop order for
integrands and hold for generic minimally coupled gauge theories with possible
scalar potential and Yukawa terms. By a standard argument this result indicates
a generalization of the Bern-Carrasco-Johansson relations for tree level
amplitudes exists to the integrand at all loop levels. A concrete relation is
presented at one loop. Furthermore, inspired by results in QED it is shown that
the results on generalized BCFW shifts of tree level amplitudes imply relations
for the so-called rational, bubble and triangle terms of one loop amplitudes in
pure Yang-Mills theory. Bubble and triangle terms for instance are shown to
obey a five photon decoupling identity, while a three photon decoupling
identity is demonstrated for the rational terms. Along the same lines recently
conjectured relations for helicity equal amplitudes at one loop are shown to
generalize to helicity independent relations for the massive box coefficient of
the rational terms.Comment: 69 pages, 27 figure
A factorization approach to next-to-leading-power threshold logarithms
Threshold logarithms become dominant in partonic cross sections when the selected final state forces gluon radiation to be soft or collinear. Such radiation factorizes at the level of scattering amplitudes, and this leads to the resummation of threshold logarithms which appear at leading power in the threshold variable. In this paper, we consider the extension of this factorization to include effects suppressed by a single power of the threshold variable. Building upon the Low-Burnett-Kroll-Del Duca (LBKD) theorem, we propose a decomposition of radiative amplitudes into universal building blocks, which contain all effects ultimately responsible for next-to-leading-power (NLP) threshold logarithms in hadronic cross sections for electroweak annihilation processes. In particular, we provide a NLO evaluation of the radiative jet function, responsible for the interference of next-to-soft and collinear effects in these cross sections. As a test, using our expression for the amplitude, we reproduce all abelian-like NLP threshold logarithms in the NNLO Drell-Yan cross section, including the interplay of real and virtual emissions. Our results are a significant step towards developing a generally applicable resummation formalism for NLP threshold effects, and illustrate the breakdown of next-to-soft theorems for gauge theory amplitudes at loop level