Virtual Photon Correction to the K+→π+π0π0K^+\to\pi^+\pi^0\pi^0 Decay

We consider electromagnetic corrections to the non-leptonic kaon decay, $K^+\to\pi^+\pi^0\pi^0$, due to explicit virtual photons only. The decay amplitude is calculated at one-loop level in the framework of Chiral Perturbation Theory. The interest in this process is twofold: It is actually measured by the NA48 collaboration from one side, and, the value of the amplitude at the $\pi\pi$ threshold gives access to $\pi\pi$ scattering lengths from the other side. We found that the present correction is about 5 to 6% the value of the Born amplitude squared. Combined with another piece published recently, this fixes the size of isospin breaking correction to the amplitude squared to 7% its one-loop level value in the absence of isospin breaking and at the center of Dalitz plot.Comment: 29 pages, 1 LaTeX file, 1 pdf file including all figure

Electron Mobility and Magneto Transport Study of Ultra-Thin Channel Double-Gate Si MOSFETs

We report on detailed room temperature and low temperature transport properties of double-gate Si MOSFETs with the Si well thickness in the range 7-17 nm. The devices were fabricated on silicon-on-insulator wafers utilizing wafer bonding, which enabled us to use heavily doped metallic back gate. We observe mobility enhancement effects at symmetric gate bias at room temperature, which is the finger print of the volume inversion/accumulation effect. An asymmetry in the mobility is detected at 300 K and at 1.6 K between the top and back interfaces of the Si well, which is interpreted to arise from different surface roughnesses of the interfaces. Low temperature peak mobilities of the reported devices scale monotonically with Si well thickness and the maximum low temperature mobility was 1.9 m2/Vs, which was measured from a 16.5 nm thick device. In the magneto transport data we observe single and two sub-band Landau level filling factor behavior depending on the well thickness and gate biasing

Matching the Electroweak Penguins Q7Q_7, Q8Q_8 and Spectral Correlators

Exact analytical expressions for the $\Delta S=1$ coupling \im G_E in terms of observable spectral functions are given. This coupling determines the size of the $\Delta I=3/2$ contribution to $\epsilon'$. We show analytically how the scheme-dependence and scale dependences vanish to all orders in $1/N_c$ and NLO in $\alpha_S$ explicitly both for $Q_7$ and $Q_8$. Numerical results are derived for both $Q_7$ and $Q_8$ from the $\tau$-data and known results on the scalar spectral functions. In particular we study the effect of all higher dimension operators. The coefficients of the leading operators in the OPE of the needed correlators are derived to NLO in $\alpha_S$.Comment: 38 pages, JHEP.cls,Changes: mistake in the calculations of the OPE coefficients corrected, numerical results: OPAL data discussed more extensively and analysis of ALEPH data extended and comparison with earlier work rewritte

The B_K Kaon Parameter in the 1/N_c Expansion

We present work going on calculating the kaon B_K parameter in the 1/N_c expansion. The goal of this work is to analyze analytically in the presence of chiral corrections this phenomenologically very important parameter. We present the method used and preliminary results for the chiral limit value for which we get the invariant \hat B_K^\chi=0.29 \pm 0.15. We also give some analytical indications of why the large N_c prediction of \hat B_K= 3/4 may have small 1/N_c corrections in the real case.Comment: Invited Talk given by J.P. at the "Large N_c QCD Workshop", 5-9 July 2004, Trento, Ital

Charged Kaon K -> 3 pi CP Violating Asymmetries

First full next-to-leading order analytical results in Chiral Perturbation Theory for the charged Kaon K -> 3 pi slope g and decay rates CP-violating asymmetries are presented. We discuss the constraints that a measurement of these asymmetries would impose on the Standard Model calculations of epsilon_K' and the kind of information it can provide on Im G_8, Im (e^2 G_E) and higher order weak couplings.Comment: Invited Talk given by J.P. at 32nd ICHEP, 16-22 August 2004, Beijing, China. 7 pages, 3 figures. Corrected first name of one autho

Determination of |V_us| from hadronic tau decays

The recent update of the strange spectral function and the moments of the invariant mass distribution by the OPAL collaboration from hadronic tau decay data are employed to determine |V_us| as well as m_s. Our result, |V_us|=0.2208\pm0.0034, is competitive to the standard extraction of |V_us| from K_e3 decays and to the new proposals to determine it. Furthermore, the error associated to our determination of |V_us| can be reduced in the future since it is dominated by the experimental uncertainty that will be eventually much improved by the B-factories hadronic tau data. Another improvement that can be performed is the simultaneous fit of both |V_us| and m_s to a set of moments of the hadronic tau decays invariant mass distribution, which will provide even a more accurate determination of both parameters.Comment: 6 pages. Invited talk given by E.G. at the XXXXth Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 5-12 Mar 200