相关论文: K_L to \pi^+ \pi^- e^+ e^-
The data on the form factors of the $K_{e4}$ decay permit to fix a value of the non-specified in the theory parameter entering in the lagrangian of the system of $0^+$ and $0^-$ mesons . Then, for a mass of the lightest $\sigma$-meson we…
The electromagnetic form factors of charged and neutral kaons are strongly constrained by their low-energy singularities, in the isovector part from two-pion intermediate states and in the isoscalar contribution in terms of $\omega$ and…
We analyse the rare kaon decays $K_S \to \gamma\gamma$ and $K_S \to \gamma\ell^+\ell^-$ $(\ell = e \mbox{ or } \mu)$ in a dispersive framework in which the weak Hamiltonian carries momentum. Our analysis extends predictions from lowest…
An improved update of the structure and decays of $\rho^0$, $\omega$ and $\phi$ mesons based on a chiral SU(3) Lagrangian, including anomaly terms is presented. We demonstrate that a consistent and quantitatively successful description of…
A theoretical description of the differential decay spectrum for the decay tau- -> nu_tau K_S pi-, which is based on the contributing K pi vector and scalar form factors F_+^{K pi}(s) and F_0^{K pi}(s) being calculated in the framework of…
The CP conserving amplitudes for the decays $K\to3\pi$ are calculated in Chiral Perturbation Theory at the next-to-leading order. We present the expressions in a compact form with single parameter functions only. These expressions are then…
Pion-nucleon scattering, pion photoproduction, and nucleon Compton scattering are analyzed within a scheme based on the chiral Lagrangian. Partial-wave amplitudes are obtained by an analytic extrapolation of subthreshold reaction amplitudes…
The rare decay $K_L\to\pi^0\nu\bar\nu$ is dominated by direct CP violation and can be computed with extraordinarily high precision. In principle also a CP conserving contribution to this process can arise within the Standard Model. We…
We investigate the form factors and decay rates for the semileptonic decays of the kaon($K_{l3})$ using the light-front quark model. The form factors $f_{\pm}(q^{2})$ are calculated in $q^{+}=0$ frame and analytically continued to the…
The recent precise measurements of the $e^+e^-\to K_SK_L$ and $e^+e^-\to K^+K^-$ cross sections and the hadronic spectral function of the $\tau^-\to K^-K_S\nu_\tau$ decay are used to extract the isoscalar and isovector electromagnetic kaon…
We present a comprehensive calculation of the $K_L\to\gamma^*\gamma^*$ form factor in dispersion theory, using input from the leptonic decays $K_L\to\ell^+\ell^-\gamma$, $K_L\to \ell_1^+\ell_1^-\ell_2^+\ell_2^-$, the hadronic mode $K_L\to…
We consider a process $K_{L e5} ( K_{L} \rightarrow \pi^{0} \pi^{0} \pi^{\pm} e^{\mp} \nu )$ as a standard model background to the experiment $K_{L} \rightarrow \pi^{0} \mu^{\pm} e^{\mp}$, which seeks for possible violation of lepton family…
We compute the form factors parametrizing radiative leptonic decays of heavy mesons B^+\to\gamma e^+\nu for photon energies much larger than \Lambda_{QCD}, where perturbative QCD methods for exclusive processes can be combined with the…
$K_{\ell 3}$ and $\pi_{e 3}$ transition form factors are calculated as an application of Dyson-Schwinger equations. The role of nonanalytic contributions to the quark--W-boson vertex is elucidated. A one-parameter model for this vertex…
CP violation leads to a difference between the parameters $g^+$ and $g^-$ describing the energy distributions of the charged pions produced in the $K^+ \to\pi^0 \pi^0 \pi^+$ and $K^- \to \pi^0\pi^0 \pi^-$ decays. We study the difference…
The form factors for semi-leptonic B decays, $\bar{B}\to\pi l\bar{\nu}_l$, are calculated under collinear factorization approach. The end-point divergences are regularized by a $\xi$-regularization, where $\xi$ means the collinear fraction…
The nucleon isovector electromagnetic form factors are calculated up to next-to-next-to-leading order by combining relativistic chiral perturbation theory (ChPT) of pion, nucleon, and $\Delta$(1232) with dispersion theory. We specifically…
In an analysis of a 2.92~fb$^{-1}$ data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be $\mathcal B(D^0 \to K^-e^+\nu_e)=(3.505\pm 0.014 \pm…
We consider the process $K_L \ra \mu^\pm e^\mp \nu \overline{\nu}$ at next to leading order in chiral perturbation theory. This process occurs in the standard model at second order in the weak interaction and constitutes a potential…
We investigate the transition formfactors for the B -> K^* l^+ l^- (l = mu, tau) decay in the light cone QCD. It is found that the light cone and 3-point QCD sum rules analyses for some of the formfactors for the decay B -> K^* l^+ l^- lead…