Related papers: The reaction e+e- --> e+e-pi+pi- and the pion form…
The pion electromagnetic form factor at spacelike momentum transfer is calculated in relativistic impulse approximation using the Covariant Spectator Theory. The same dressed quark mass function and the equation for the pion bound-state…
We analyze the radiative pion decay pi+ -> e+ nu_e gamma within nonlocal chiral quark models that include wave function renormalization. In this framework we calculate the vector and axial-vector form factors FV and FA at q^2=0 --where q^2…
We extract the K^+-->pi^+e^+e^- amplitude scale at q^2=0 from the recent Brookhaven E865 high-statistics data. We find that the q^2=0 scale is fitted in excellent agreement with the theoretical long-distance amplitude. Lastly, we find that…
We consider a model with $\rho\pi\pi$, $\rho KK$, and gauge-invariant $\rho\gamma$ couplings and obtain the pion form factor $F_\pi$ at timelike momentum transfers by resummation of pion and kaon loops. We use a dispersion representation…
We have measured the $\pi^+\to {\rm e}^+\nu\gamma$ branching ratio over a wide region of phase space, based on a total of 65,460 events acquired using the PIBETA detector. Minimum-$\chi^2$ fits to the measured $(E_{e^+},E_\gamma)$ energy…
The measurement of the pion form factor and, more generally, of the cross section for electron--positron annihilation into hadrons through the radiative return has become an important task for high luminosity colliders such as the $\Phi$-…
We use recent data on K^+ -> pi^+e^+e^-, together with known values for the pion form factor, to derive the kaon electromagnetic form factor for 0 <q^2 <0.125 (GeV/c)^2. The results are then compared with predictions of the Linear sigma…
We present a sample of results for the cross sections of several processes of low energetic $e^+e^-$ annihilation into final states containing pions accompanied by one or two photons, or a light lepton pair. The results, which have been…
We present a study of the reaction $\pi^-p \to ne^+e^-$ for $\sqrt{s}=1.49\,\textrm{GeV}$, including non-resonant Born terms and contributions of the $N(1440)$, $N(1520)$, $N(1535)$ resonances ($R$), using an effective-Lagrangian model,…
The pion electromagnetic form factor is calculated at lower and higher momentum transfer in order to explore constituent quark models and the differences among those models. In particular, the light-front constituent quark model is utilized…
A model independent formalism for the electron positron annihilation reaction $e^++e^-\to a_1(1260)+\pi $ has been derived. The differential and total cross sections and the elements of the spin--density matrix of the $a_1$-meson were…
The two-photon-exchange (TPE) effects in the process $e^+e^- \rightarrow \pi^+\pi^-$ at large momentum transfer are discussed within the perturbative QCD (pQCD). The contributions from the twist-2 and twist-3 distribution amplitudes (DAs)…
A new formula for the pion form factor F_pi is proposed which takes into account the pseudoscalar meson loops and the mixing among rho(770), rho(1450), and rho(1700). The expression possesses correct analytical properties and can be used in…
The electromagnetic form factor of the pion is calculated in a pseudoscalar field theoretical model which constituent quarks. We extract the form factor using the "+" component of the electromagnetic current in the light-cone formalism. For…
The cross section for the process $e^+e^-\to\pi^+\pi^-$ is measured in the c.m. energy range 1.04-1.38 GeV from 995 000 selected collinear events including 860000 $e^+e^-$ events, 82000 $\mu^+\mu^-$ events, and 33000 $\pi^+\pi^-$ events.…
In the paper, the electromagnetic off-shell pion form factors in the Bethe-Salpeter formalism with a separable kernel are considered. Different types of vertex functions of a pion are investigated. The separable kernel of the…
We have measured the cross section of the radiative process e+e- -> pi+pi-gamma with the KLOE detector at the Frascati phi-factory DAPHNE, from events taken at a CM energy W=1 GeV. Initial state radiation allows us to obtain the cross…
Cross sections for the reaction ${^1}$H($e,e'\pi^+$)$n$ were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF high-intensity, continous electron beam in order to determine the charged pion form…
The Monte Carlo generator EKHARA allows to simulate the process (e+e- to e+e-pi0) at energies of meson factories. We review the motivation, describe the current status of the generator, and discuss features, which will appear in the…
The strong and electromagnetic corrections to $\rho-\omega$ mixing are calculated using a SU(2) version of resonance chiral theory up to next-to-leading orders in $1/N_C$ expansion, respectively. Up to our accuracy, the effect of the…