476 research outputs found
Reconstruction of metabolic networks from high-throughput metabolite profiling data: in silico analysis of red blood cell metabolism
We investigate the ability of algorithms developed for reverse engineering of
transcriptional regulatory networks to reconstruct metabolic networks from
high-throughput metabolite profiling data. For this, we generate synthetic
metabolic profiles for benchmarking purposes based on a well-established model
for red blood cell metabolism. A variety of data sets is generated, accounting
for different properties of real metabolic networks, such as experimental
noise, metabolite correlations, and temporal dynamics. These data sets are made
available online. We apply ARACNE, a mainstream transcriptional networks
reverse engineering algorithm, to these data sets and observe performance
comparable to that obtained in the transcriptional domain, for which the
algorithm was originally designed.Comment: 14 pages, 3 figures. Presented at the DIMACS Workshop on Dialogue on
Reverse Engineering Assessment and Methods (DREAM), Sep 200
Semileptonic b --> u decays: lepton invariant mass spectrum
We compute O(alpha_s^2) QCD corrections to the lepton invariant mass spectrum
in the decay b --> u l nu_l, relevant for the determination of the CKM matrix
element |V_{ub}|. Our method can also be used to evaluate moments of the lepton
energy distribution with an O(alpha_s^2) accuracy. The abelian part of our
result gives the neutrino invariant mass spectrum in the muon decay and, upon
integration, the O(alpha^2) correction to the muon lifetime.Comment: 5 pages, revte
Higgs Decay to Top Quarks at O(\alpha_s^2)
Three-loop corrections to the scalar and pseudo-scalar current correlator are
calculated. By applying the large momentum expansion mass terms up to order
(m^2/q^2)^4 are evaluated analytically. As an application O(\alpha_s^2)
corrections to the decay of a scalar and pseudo-scalar Higgs boson into top
quarks are considered. It is shown that for a Higgs mass not far above the
threshold these higher order mass corrections are necessary to get
reliable results.Comment: Latex, 20 pages, 14 ps-figures. The complete paper, including
figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints
Three-loop \beta-functions for top-Yukawa and the Higgs self-interaction in the Standard Model
We analytically compute the dominant contributions to the \beta-functions for
the top-Yukawa coupling, the strong coupling and the Higgs self-coupling as
well as the anomalous dimensions of the scalar, gluon and quark fields in the
unbroken phase of the Standard Model at three-loop level. These are mainly the
QCD and top-Yukawa corrections. The contributions from the Higgs
self-interaction which are negligible for the running of the top-Yukawa and the
strong coupling but important for the running of the Higgs self-coupling are
also evaluated.Comment: 22 pages, 7 figures. Few extra citations are added; the plots are
improved. Results in computer readable form can be retrieved from
http://www-ttp.particle.uni-karlsruhe.de/Progdata/ttp12/ttp12-012
Theoretical Aspects of Standard-Model Higgs-Boson Physics at a Future e^+ e^- Linear Collider
The Higgs boson is the missing link of the Standard Model of elementary
particle physics. We review its decay properties and production mechanisms at a
future e^+ e^- linear collider and its e^- e^-, e^+- gamma, and gamma gamma
modes, with special emphasis on the influence of quantum corrections. We also
discuss how its quantum numbers and couplings can be extracted from the study
of appropriate final states.Comment: 23 pages (Latex), 15 figures (Postscript), to appear in Int. J. Mod.
Phys.
Performance of a 229 Thorium solid-state nuclear clock
The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as an
etalon transition in a new type of optical frequency standard. Here we discuss
the construction of a "solid-state nuclear clock" from Thorium nuclei implanted
into single crystals transparent in the vacuum ultraviolet range. We
investigate crystal-induced line shifts and broadening effects for the specific
system of Calcium fluoride. At liquid Nitrogen temperatures, the clock
performance will be limited by decoherence due to magnetic coupling of the
Thorium nucleus to neighboring nuclear moments, ruling out the commonly used
Rabi or Ramsey interrogation schemes. We propose a clock stabilization based on
counting of flourescence photons and present optimized operation parameters.
Taking advantage of the high number of quantum oscillators under continuous
interrogation, a fractional instability level of 10^{-19} might be reached
within the solid-state approach.Comment: 28 pages, 9 figure
High-Precision Charm-Quark Mass and QCD Coupling from Current-Current Correlators in Lattice and Continuum QCD
We use lattice QCD simulations, with MILC gluon configurations and HISQ
c-quark propagators, to make very precise determinations of moments of
charm-quark pseudoscalar, vector and axial-vector correlators. These moments
are combined with new four-loop results from continuum perturbation theory to
obtain several new determinations of the MSbar mass of the charm quark and of
the MSbar coupling. We find m_c(3GeV)=0.986(10)GeV, or, equivalently,
m_c(m_c)=1.268(9)GeV, both for n_f=4 flavors; and
alpha_msb(3GeV,n_f=4)=0.251(6), or, equivalently,
alpha_\msb(M_Z,n_f=5)=0.1174(12). The new mass agrees well with results from
continuum analyses of the vector correlator using experimental data for e+e-
annihilation (instead of using lattice QCD simulations). These lattice and
continuum results are the most accurate determinations to date of this mass.
Ours is also one of the most accurate determinations of the QCD coupling by any
method.Comment: 12 pages, 5 figures, 5 table
Heavy-Light Meson Decay Constant from QCD Sum Rules in Three-Loop Approximation
In this paper we compute the decay constant of the pseudo-scalar heavy-light
mesons in the heavy quark effective theory framework of QCD sum rules. In our
analysis we include the recently evaluated three-loop result of order
for the heavy-light current correlator. The value of the bottom
quark mass, which essentially limits the accuracy of the sum rules for
meson, is extracted from the nonrelativistic sum rules for
resonances in the next-to-next-to-leading approximation. We find stability of
our result with respect to all types of corrections and the specific form of
the sum rule which reduces the uncertainty. Our results MeV and
MeV for the and meson decay constants are in impressive
agreement with recent lattice calculations.Comment: minor editorial changes, references added, to appear in PR
Virtual Top-Quark Effects on the H->bb-bar Decay at Next-to-Leading Order in QCD
By means of a heavy-top-quark effective Lagrangian, we calculate the
three-loop corrections of O(alpha_s^2 G_F M_t^2) to the H->bb-bar partial decay
width of the standard-model Higgs boson with intermediate mass M_H<<2M_t. We
take advantage of a soft-Higgs theorem to construct the relevant coefficient
functions. We present our result both in the MS-bar and on-shell schemes of
mass renormalization. The MS-bar formulation turns out to be favourable with
regard to the convergence behaviour. We also test a recent idea concerning the
naive non-abelianization of QCD.Comment: 8 pages (Latex), 5 figures (Postscript
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