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 (g−2)μ(g-2)_{\mu} with holographic models of QCD

We study the anomalous electromagnetic pion form factor $F_{\pi^0\gamma^*\gamma^*}$ 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 $F_{\pi^0\gamma^*\gamma^*}$, 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 $(g-2)_{\mu}$ 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 $a_{\mu}^{\pi^0}=6.54(25)\cdot 10^{-10}$, where the error is driven by the linear slope of $F_{\pi^0\gamma^*\gamma^*}$, soon to be measured with precision at KLOE-2. Our numerical analysis also indicates that large values of the magnetic susceptibility $\chi_0$ are disfavored, therefore pointing at a mild effect from the pion off-shellness. However, in the absence of stronger bounds on $\chi_0$, an additional $(10-15)$ systematic uncertainty on the previous value for $a_\mu^{\pi^0}$ 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

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 ‘safety’ 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