1,720 research outputs found
Form factor in K+ --> pi+ pi0 gamma: interference versus direct emission
We analyze the effect of a form factor in the magnetic contribution to K+ -->
pi+ pi0 gamma. We emphasize how this can show up experimentally: in particular
we try to explore the difference between a possible interference contribution
and a form factor in the magnetic part. The form factor used for K+ --> pi+ pi0
gamma is analogous to the one for KL --> pi+ pi- gamma, experimentally well
established.Comment: 9 pages revtex, 10 eps figures; improved presentation of theoretical
and experimental status; refs. adde
Long-distance contribution to the forward-backward asymmetry in decays K+ --> pi+ l+ l-
The long-distance contribution via the two-photon intermediate state to the
forward-backward asymmetries in decays K+ --> pi+ l+ l- (l=e and mu) has been
studied within the standard model. In order to evaluate the dispersive part of
the K+ --> pi+ gamma* gamma* --> pi+ l+ l- amplitude, we employ a
phenomenological form factor to soften the ultraviolet behavior of the
transition. It is found that, this long-distance transition, although subject
to some theoretical uncertainties, can lead to significant contributions to the
forward-backward asymmetries, which could be tested in the future high-precise
experiments.Comment: 13 pages, 5 figure
The hadronic light by light contribution to the with holographic models of QCD
We study the anomalous electromagnetic pion form factor
with a set of holographic models. By comparing with
the measured value of the linear slope, some of these models can be ruled out.
From the remaining models we obtain predictions for the low-energy quadratic
slope parameters of , currently out of experimental
reach but testable in the near future. We find it particularly useful to encode
this low-energy information in a form factor able to satisfy also QCD
short-distance constraints. We choose the form factor introduced by D'Ambrosio,
Isidori and Portoles in kaon decays, which has the right short distance for a
particular value of the quadratic slope, which is later shown to be compatible
with our holographic predictions. We then turn to a determination of the
(dominant) pion exchange diagram in the hadronic light by light scattering
contribution to the muon anomalous magnetic moment. We quantify the theoretical
uncertainty in coming from the different input we use: QCD short
distances, experimental input and low-energy holographic predictions. We also
test the pion-pole approximation. Our final result is
, where the error is driven by the
linear slope of , soon to be measured with precision
at KLOE-2. Our numerical analysis also indicates that large values of the
magnetic susceptibility are disfavored, therefore pointing at a mild
effect from the pion off-shellness. However, in the absence of stronger bounds
on , an additional systematic uncertainty on the previous
value for cannot be excluded.Comment: 20 pages, 5 figures. Substantial improvements throughout the text to
match the published version. Enhanced discussion of the analysis in Section
IV with the addition of two appendices. Conclusions unchange
Chronic venous insufficiency strengthens the thrombo-embolic risk in congestive heart failure in elderly patients
FROM THE DIGITAL TWIN OF ARCHITECTURAL HERITAGE TO THE DEFINITION OF THE CONSTRAINT MAPS. THE CASE STUDY OF THE CASTELLO SFORZESCO IN MILAN
The work presented here is part of the widespread digitisation process that is affecting the world of architecture and cultural heritage. The text reports part of the activities carried out on the Castello Sforzesco in Milan, in collaboration with its Superintendence bodies. This work proposes an innovative way to draft, in a digital environment, 3D constraint maps, capable of describing and protecting the complex system of structures in that area, especially in the subsoil. The activity began with the creation of a georeferenced 3D model of all the existing architectural elements in the analyzed area of the Castle. The work was carried out on the northwest corner of the fortress, the area between the Torre della Colubrina and the Porta del Soccorso. The modeling activity was based both on data obtained from surveys and historical documentation describing structures that are no longer visible. From the 3D model, it was then possible to obtain all useful data to draw up constraint maps in GIS (Geographic Information System) environment. This latter allows multiple interactions both with the normal surface cartographic information (Topographic Database and others) and with the multitude of datasets available for managing the territory and its subsystems. The constraints consider a âsafetyâ offset, applied in all three directions. These maps describe the various three-dimensional areas, referring to the different structures present in the subsoil, within which it is recommended to operate with extreme caution, in relation to the position and conformation of the same identified assets
The s ---> d gamma decay in and beyond the Standard Model
The New Physics sensitivity of the s ---> d gamma transition and its
accessibility through hadronic processes are thoroughly investigated. Firstly,
the Standard Model predictions for the direct CP-violating observables in
radiative K decays are systematically improved. Besides, the magnetic
contribution to epsilon prime is estimated and found subleading, even in the
presence of New Physics, and a new strategy to resolve its electroweak versus
QCD penguin fraction is identified. Secondly, the signatures of a series of New
Physics scenarios, characterized as model-independently as possible in terms of
their underlying dynamics, are investigated by combining the information from
all the FCNC transitions in the s ---> d sector.Comment: 54 pages, 14 eps figure
EWPD Constraints on Flavor Symmetric Vector Fields
Electroweak precision data constraints on flavor symmetric vector fields are
determined. The flavor multiplets of spin one that we examine are the complete
set of fields that couple to quark bi-linears at tree level while not initially
breaking the quark global flavor symmetry group. Flavor safe vector masses
proximate to, and in some cases below, the electroweak symmetry breaking scale
are found to be allowed. Many of these fields provide a flavor safe mechanism
to explain the t tbar forward backward anomaly, and can simultaneously
significantly raise the allowed values of the Standard Model Higgs mass
consistent with electroweak precision data.Comment: Matches version published in JHE
About one long-range contribution to K+ -> pi+ l+ l- decays
We investigate the mechanism of K+ -> pi+ l+ l- (l= e, mu) decays in which a
virtual photon is emitted either from the incoming K+ or the outgoing pi+. We
point out some inconsistencies with and between two previous calculations,
discuss the possible experimental inputs, and estimate the branching fractions.
This mechanism alone fails to explain the existing experimental data by more
than one order-of-magnitude. But it may show itself by its interference with
the leading long-range mechanism dominated by the a_1^+ and rho^0 mesons.Comment: 12 pages, RevTeX, epsf.sty, 2 embedded figure
Charge asymmetry in K+- --> \pi+-\gamma\gamma induced by the electromagnetic penguin operators
The CP-violating charge asymmetry in decays K+- --> \pi+- \gamma\gamma, which
is induced by the electromagnetic penguin operators, has been studied both in
thestandard model and in its extensions. Because of a large enhancement of the
Wilson coefficients of the electromagnetic penguin operators in the
supersymmetric extensions of the standard model, a significant upper bound on
this charge asymmetry could be expected, and thus high precision measurements
of this interesting CP-violating quantity might explore new physics effects
beyond the standard model.Comment: LaTeX, 10 pages, minor changes, Published versio
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