Related papers: Radiative Tail in $\pi_{e2}$ Decay and Some Commen…
We have studied radiative pion decays Pi+ -> e+ nu gamma in three broad kinematic regions using the PIBETA detector and a stopped pion beam. Based on Dalitz distributions of 42,209 events we have evaluated absolute Pi -> e nu gamma…
The study of the cosmic ray positron flux has attracted intense attention in recent years, especially because the observations suggest that it could receive contributions from sources such as pulsars or the self--annihilation or decay of…
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for radiative Ke3 decays (neutral kaons). Special emphasis is given on the stability of the inner…
We carry out a detailed study of the branching fractions and lepton pair invariant-mass spectrum of \tau^- ->\pi^- \nu_\tau l^+l^- decays (l=e,\mu). In addition to the model-independent (QED) contributions, we include the…
With usage of the Low theorem the general expression for amplitude of radiative kaon decay \k+ \to \pi+\pi0\gamma is determined.
The pattern of chiral symmetry breaking is exploited to compute vector and axial-vector pion matrix elements in a uniform magnetic field. Our results are model independent, and thereby constitute low-energy theorems that must be obeyed by…
We consider radiative \beta--decay of the neutron in heavy baryon chiral perturbation theory, with an extension including explicit \Delta degrees of freedom. We compute the photon energy spectrum as well as the photon polarization; both…
We consider the impact of O(alpha^2) hadronic corrections to the energy spectrum of the decay electron in muon decay. We find that the correction can be described, within good approximation, by a linear function in the electron energy.…
Within Chiral Perturbation Theory, we study elastic pion scattering in the I=0, J=2, channel, whose main features are the f2(1270) resonance and the vanishing of the lowest order. By means of a chiral model that includes an explicit…
We discuss radiative corrections to K_{e3} and pi_{e3} decays within chiral perturbation theory with virtual photons and leptons. We then present the extraction of the CKM elements V_{us} and V_{ud} using the presently available…
Recently, much work has been devoted to the calculation of order $\alpha$ corrections to the decay rate of pionium, the $\pi^+ \pi^-$ bound state. In previous calculations, nonrelativistic QED corrections were neglected since they start at…
Recent experimental data on tau decays are used to reconstruct the difference in hadronic spectral densities with vector and axial-vector quantum numbers. The saturation of Das-Mathur-Okubo and Weinberg sum rules is studied. Two methods of…
Positronium decay rates are computed at the one-loop level, using convolution-type factorized amplitudes. The dynamics of this factorization is probed with dispersion relations, showing that unallowed approximations are usually made, and…
Some atomic decays of elementary particles with pionium ($\pi^+\pi^-$-dimesoatom) in the final state are considered. Only for K-meson atomic decays are the corresponding branching ratios big enough to make their experimental study…
We briefly summarize current experimental and theoretical results on the two important processes of the low-energy hadron physics involving neutral pions, the rare decay $\pi^0\to e^+e^-$ and the Dalitz decay of $\pi^0$, and provide a new…
We calculate the one-photon loop radiative corrections to the neutral pion-pair photoproduction process $\pi^-\gamma \to \pi^-\pi^0\pi^0$. At leading order this reaction is governed by the chiral pion-pion interaction. Since the chiral…
The differential cross sections for $\pi^- p \to \gamma n$ and $\pi^+ n \to \gamma p$ are computed up to $O(p^3)$ in heavy baryon chiral perturbation theory (HBChPT). The expressions at $O(p)$ and $O(p^2)$ have no free parameters. There are…
We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum…
Predictions for the muon decay spectrum are usually derived from the derivative-free Hamiltonian. However, it is not the most general form of the possible interactions. Additional simple terms with derivatives can be introduced. In this…
We have calculated the decay $\tau \rightarrow \nu \pi(K) \gamma$. We present the photon energy spectrum, the meson-photon invariant mass spectrum and the integrated rate as a function of a photon energy cut or an invariant mass cut. Both…