3,028 research outputs found
Charmless Two-body Baryonic B Decays
We study charmless two-body baryonic B decays in a diagramatic approach.
Relations on decay amplitudes are obtained. In general there are more than one
tree and more than one penguin amplitudes. The number of independent amplitudes
can be reduced in the large m_B limit. It leads to more predictive results.
Some prominent modes for experimental searches are pointed out.Comment: 15 pages, 2 figures. To appear in Phys. Rev.
Exploiting unmeasured disturbance signals in identifiability of linear dynamic networks with partial measurement and partial excitation
Identifiability conditions for networks of transfer functions require a sucientnumber of external excitation signals, which are typically measured reference signals. In this abstract, we introduce an equivalent network model structure to address the contribution of unmeasured noises to identifiability analysis in the setting with partial excitation and partial measurement. With this model structure, unmeasured disturbance signals can be exploited as excitation sources, which leads to less conservative identifiability conditions
Folded Supersymmetry and the LEP Paradox
We present a new class of models that stabilize the weak scale against
radiative corrections up to scales of order 5 TeV without large corrections to
precision electroweak observables. In these `folded supersymmetric' theories
the one loop quadratic divergences of the Standard Model Higgs field are
cancelled by opposite spin partners, but the gauge quantum numbers of these new
particles are in general different from those of the conventional
superpartners. This class of models is built around the correspondence that
exists in the large N limit between the correlation functions of supersymmetric
theories and those of their non-supersymmetric orbifold daughters. By
identifying the mechanism which underlies the cancellation of one loop
quadratic divergences in these theories, we are able to construct simple
extensions of the Standard Model which are radiatively stable at one loop.
Ultraviolet completions of these theories can be obtained by imposing suitable
boundary conditions on an appropriate supersymmetric higher dimensional theory
compactified down to four dimensions. We construct a specific model based on
these ideas which stabilizes the weak scale up to about 20 TeV and where the
states which cancel the top loop are scalars not charged under Standard Model
color. Its collider signatures are distinct from conventional supersymmetric
theories and include characteristic events with hard leptons and missing
energy.Comment: 18 pages, 5 figures, references correcte
Single module identifiability in linear dynamic networks with partial excitation and measurement
Identifiability of a single module in a network of transfer functions is determined by whether a particular transfer function in the network can be uniquely distinguished within a network model set, on the basis of data. Whereas previous research has focused on the situations that all network signals are either excited or measured, we develop generalized analysis results for the situation of partial measurement and partial excitation. As identifiability conditions typically require a sufficient number of external excitation signals, this article introduces a novel network model structure such that excitation from unmeasured noise signals is included, which leads to less conservative identifiability conditions than relying on measured excitation signals only. More importantly, graphical conditions are developed to verify global and generic identifiability of a single module based on the topology of the dynamic network. Depending on whether the input or the output of the module can be measured, we present four identifiability conditions which cover all possible situations in single module identification. These conditions further lead to synthesis approaches for allocating excitation signals and selecting measured signals, to warrant single module identifiability. In addition, if the identifiability conditions are satisfied for a sufficient number of external excitation signals only, indirect identification methods are developed to provide a consistent estimate of the module. All the obtained results are also extended to identifiability of multiple modules in the network.</p
Statistical and Dynamic Models of Charge Balance Functions
Charge balance functions, which identify balancing particle-antiparticle
pairs on a statistical basis, have been shown to be sensitive to whether
hadronization is delayed by several fm/c in relativistic heavy ion collisions.
Results from two classes of models are presented here, microscopic hadronic
models and thermal models. The microscopic models give results which are
contrary to recently published pi+pi- balance functions from the STAR
collaboration, whereas the thermal model roughly reproduce the experimental
results. This suggests that charge conservation is local at breakup, which is
in line with expectations for a delayed hadronization. Predictions are also
presented for balance functions binned as a function of Q_inv.Comment: 12 pages 6 figure
A Necessary Condition for Network Identifiability With Partial Excitation and Measurement
This article considers dynamic networks where vertices and edges represent manifest signals and causal dependencies among the signals, respectively. We address the problem of how to determine if the dynamics of a network can be identified when only partial vertices are measured and excited. A necessary condition for network identifiability is presented, where the analysis is performed based on identifying the dependency of a set of rational functions from excited vertices to measured ones. This condition is further characterized by using an edge-removal procedure on the associated bipartite graph. Moreover, on the basis of necessity analysis, we provide a necessary and sufficient condition for identifiability in circular networks.</p
Asymmetry Parameter of the by Analyzing the Transition Form Factors within QCD
Separating the mixture of the and states, the
transition form factors are calculated in
the three-point QCD sum rules approach. The longitudinal, transverse and total
decay widths as well as the asymmetry parameter, characterizing the
polarization of the axial and the branching ratio for these
decays are evaluated.Comment: 25 pages, 3 figures, 3 table
Flavor symmetry analysis of charmless B --> VP decays
Based upon flavor SU(3) symmetry, we perform global fits to charmless
B decays into one pseudoscalar meson and one vector meson in the final
states. We consider different symmetry breaking schemes and find that the one
implied by na{\"i}ve factorization is slightly favored over the exact symmetry
case. The vertex of the unitarity triangle (UT)
constrained by our fits is consistent with other methods within errors. We have
found large color-suppressed, electroweak penguin and singlet penguin
amplitudes when the spectator quark ends up in the final-state vector meson.
Nontrivial relative strong phases are also required to explain the data. The
best-fit parameters are used to compute branching ratio and CP asymmetry
observables in all of the decay modes, particularly those in the decays
to be measured at the Tevatron and LHC experiments.Comment: 23 pages and 2 plots; updated with ICHEP'08 data and expanded in
discussions and reference
The Power of Duples (in Self-Assembly): It's Not So Hip To Be Square
In this paper we define the Dupled abstract Tile Assembly Model (DaTAM),
which is a slight extension to the abstract Tile Assembly Model (aTAM) that
allows for not only the standard square tiles, but also "duple" tiles which are
rectangles pre-formed by the joining of two square tiles. We show that the
addition of duples allows for powerful behaviors of self-assembling systems at
temperature 1, meaning systems which exclude the requirement of cooperative
binding by tiles (i.e., the requirement that a tile must be able to bind to at
least 2 tiles in an existing assembly if it is to attach). Cooperative binding
is conjectured to be required in the standard aTAM for Turing universal
computation and the efficient self-assembly of shapes, but we show that in the
DaTAM these behaviors can in fact be exhibited at temperature 1. We then show
that the DaTAM doesn't provide asymptotic improvements over the aTAM in its
ability to efficiently build thin rectangles. Finally, we present a series of
results which prove that the temperature-2 aTAM and temperature-1 DaTAM have
mutually exclusive powers. That is, each is able to self-assemble shapes that
the other can't, and each has systems which cannot be simulated by the other.
Beyond being of purely theoretical interest, these results have practical
motivation as duples have already proven to be useful in laboratory
implementations of DNA-based tiles
The Proton Spin and Flavor Structure in the Chiral Quark Model
After a pedagogical review of the simple constituent quark model and deep
inelastic sum rules, we describe how a quark sea as produced by the emission of
internal Goldstone bosons by the valence quarks can account for the observed
features of proton spin and flavor structures. Some issues concerning the
strange quark content of the nucleon are also discussed.Comment: 59 pages with table of contents, Lecture delivered at the Schladming
Winter School (March 1997), to be published by Springer-Verlag under the
title "Computing Particle Properties" (eds. C. B. Lang and H. Gausterer
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