1,387 research outputs found
Alien Registration- Hudson, Hortense (Auburn, Androscoggin County)
https://digitalmaine.com/alien_docs/22700/thumbnail.jp
Sphaleron-Bisphaleron bifurcations in a custodial-symmetric two-doublets model
The standard electroweak model is extended by means of a second
Brout-Englert-Higgs-doublet. The symmetry breaking potential is chosen is such
a way that (i) the Lagrangian possesses a custodial symmetry, (ii) a static,
spherically symmetric ansatz of the bosonic fields consistently reduces the
Euler-Lagrange equations to a set of differential equations. The potential
involves, in particular, products of fields of the two doublets, with a
coupling constant .Static, finite energy solutions of the classical
equations are constructed. The regular, non-trivial solutions having the lowest
classical energy can be of two types: sphaleron or bisphaleron, according to
the coupling constants. A special emphasis is put to the bifurcation between
these two types of solutions which is analyzed in function of the different
constants of the model,namely of .Comment: 10 pages, 3 figure
Blocks at Your Fingertips: Blurring the Line Between Blocks and Text in GP
Visual blocks languages offer many advantages to the beginner or “casual” programmer. They eliminate syntax issues, allow the user to work with logical program chunks, provide affordances such as drop-down menus, and leverage the fact that recognition is easier than recall. However, as users gain experience and start creating larger programs, they encounter two inconvenient properties of pure blocks languages: blocks take up more screen real-estate than textual languages and dragging blocks from a palette is slower than typing.
This paper describes three experiments in blurring the line between blocks and textual code in GP, a new blocks language for casual programmers currently under development
-to-Glueball form factor and Glueball production in decays
We investigate transition form factors of meson decays into a scalar
glueball in the light-cone formalism. Compared with form factors of to
ordinary scalar mesons, the -to-glueball form factors have the same power in
the expansion of . Taking into account the leading twist light-cone
distribution amplitude, we find that they are numerically smaller than those
form factors of to ordinary scalar mesons. Semileptonic ,
and decays are subsequently investigated. We
also analyze the production rates of scalar mesons in semileptonic decays
in the presence of mixing between scalar and glueball states. The
glueball production in meson decays is also investigated and the LHCb
experiment may discover this channel. The sizable branching fraction in , or could be a clear signal for a scalar glueball
state.Comment: 17 pages, 3 figure, revtex
Probing three-dimensional surfaces force fields with atomic resolution: Measurement strategies, limitations, and artifact reduction
Cataloged from PDF version of article.Noncontact atomic force microscopy (NC-AFM) is being increasingly used to measure the interaction force between an atomically sharp probe tip and surfaces of interest, as a function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image interpretation.
In this paper, we analyze their impact on the acquired data, compare different methods to record atomic-resolution surface force fields, and determine the approaches that suffer the least from the associated artifacts. The related discussion underscores the idea that since force fields recorded by using NC-AFM always reflect the properties of both the sample and the probe tip, efforts to reduce unwanted effects of the tip on recorded data are indispensable for the extraction of detailed information about the atomic-scale properties of the surface
Understanding Scanning Tunneling Microscopy Contrast Mechanisms on Metal Oxides: A Case Study
Cataloged from PDF version of article.A comprehensive analysis of contrast formation
mechanisms in scanning tunneling microscopy (STM) experiments on
a metal oxide surface is presented with the oxygen-induced
(2√2
√2)R45 missing row reconstruction of the Cu(100) surface
as a model system. Density functional theory and electronic
transport calculations were combined to simulate the STM imaging
behavior of pure and oxygen-contaminated metal tips with structurally
and chemically different apexes while systematically varying
bias voltage and tip sample distance. The resulting multiparameter
database of computed images was used to conduct an extensive comparison with experimental data. Excellent agreement was attained for a large
number of cases, suggesting that the assumed model tips reproduce most of the commonly encountered contrast-determining effects. Specifically, we find
that depending on the bias voltage polarity, copper-terminated tips allow selective imaging of two structurally distinct surface Cu sites, while oxygenterminated
tips show complex contrasts with pronounced asymmetry and tip sample distance dependence. Considering the structural and chemical
stability of the tips reveals that the copper-terminated apexes tend to react with surface oxygen at small tip sample distances. In contrast, oxygenterminated
tips are considerably more stable, allowing exclusive surface oxygen imaging at small tip sample distances. Our results provide a conclusive
understanding of fundamental STM imaging mechanisms, thereby providing guidelines for experimentalists to achieve chemically selective imaging by
properly selecting imaging parameters
Exploring atomic-scale lateral forces in the attractive regime: a case study on graphite (0001)
Cataloged from PDF version of article.A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of lateral forces with piconewton and picometer resolution as a function of both the in-plane tip position and the vertical tip-sample distance, without limitations due to a finite contact area or to stick-slip-related sudden jumps of tip apex atoms. After reviewing the measurement principle, the data obtained in this case study are utilized to illustrate the unique insight that the method offers. In particular, the local lateral forces that are expected to determine frictional resistance in the attractive regime are found to depend linearly on the normal force for small tip-sample distances
Enhancement of h --> gamma gamma in the Two Higgs Doublet Model Type I
We show that in the Two Higgs Doublet Model (THDM) Type I the partial decay
width of h --> gamma gamma can be considerably larger than in Type II, due to
light charged scalars with a mass about 100 GeV, which are not yet excluded in
Type I. A possible enhancement of the width compared to the SM is analyzed for
different Higgs potentials, subject to constraints from tree-level unitarity,
vacuum stability and electroweak precision tests.Comment: 12 pages. v2: Sign error in eq. (19) corrected. Results and figures
for the IDM changed accordingly. Other minor corrections. References and
improved discussion of interference effects adde
Resolving the A_{FB}^b puzzle in an extra dimensional model with an extended gauge structure
It is notorious that, contrary to all other precision electroweak data, the
forward-backward asymmetry for b quarks measured in Z decays at LEP1
is nearly three standard deviations away from the predicted value in the
Standard Model; significant deviations also occur in measurements of the
asymmetry off the Z pole. We show that these discrepancies can be resolved in a
variant of the Randall-Sundrum extra-dimensional model in which the gauge
structure is extended to to allow for
relatively light Kaluza-Klein excitations of the gauge bosons. In this
scenario, the fermions are localized differently along the extra dimension, in
order to generate the fermion mass hierarchies, so that the electroweak
interactions for the heavy third generation fermions are naturally different
from the light fermion ones. We show that the mixing between the Z boson with
the Kaluza-Klein excitations allows to explain the anomaly without
affecting (and even improving) the agreement of the other precision
observables, including the partial decay width, with experimental
data. Some implications of this scenario for the ILC are summarized.Comment: 23 pages, 5 figure
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