Related papers: Pionium in the elementary particle decays
The article describes experimental status of EtaPrime->Pi+Pi-Eta and EtaPrime->Pi+Pi-Pi0 decays. A theoretical framework used for description of the decays mechanism is also reviewed. The possibilities for the measurements with WASA-at-COSY…
Non-relativisitic second-order corrections to the wave function at origin in muonic and exotic atoms are considered. The corrections are due to the electronic vacuum polarization. Such corrections are of interest due to various effective…
Pionium lifetime corrections to the nonrelativistic formula are calculated in the framework of the quasipotential-constraint theory approach. The calculation extends an earlier evaluation, made in the scheme of standard chiral perturbation…
It is pointed out that the decay of the recently observed charmonium eta_c^prime resonance, eta_c^prime -> eta_c pi pi is simply related to the well studied decay psi^prime -> J/psi pi pi and can thus be used for absolute normalization of…
We describe the $\pi\pi$ $S$-wave in $D^+ \to\pi^+ \pi^- \pi^+$ decays using a unitary model for the $\pi\pi$ Final State Interactions (FSI). The three body decay is treated as a quasi two-body process where, at the weak vertex, the D meson…
The relationship between the pionium lifetime and the $\pi\pi$ scattering lengths is established, including the sizable electromagnetic corrections. The bound state formalism that is used is that of constraint theory which provides a…
We construct an effective non-relativistic quantum field theory that describes bound states of pi+ pi- pairs and their hadronic decays. We then derive a general expression for the lifetime of the ground state at next-to-leading order in…
Strong pionic decays of baryons are studied in a non-relativistic quark model framework via a convergent (p/E) expansion of the transition operator. Results are compared to the ones obtained within a more conventional (p/m) expansion.
A next-generation rare pion decay experiment, PIONEER, is strongly motivated by several inconsistencies between Standard Model (SM) predictions and data pointing towards the potential violation of lepton flavor universality. It will probe…
Pionic beta decay \pi^+ to \pi^0 e^+ \nu_e is analyzed in chiral perturbation theory with virtual photons and leptons. All electromagnetic corrections up to order e^2 p^2 are taken into account. Theoretical results are confronted with…
The lowest order QED radiative corrections to the cross-section of the recharged process of transition of two charged pions to two neutral ones and to the pionium life time are calculated in frames of scalar QED. It is argued that the…
We calculate the width for the omega -> pi pi decay in nuclear matter in a hadronic model including mesons, nucleons and Delta isobars. We find a substantial width of the longitudinally polarized omega modes, reaching ~100MeV for mesons…
The pionic decay of a possible d'-dibaryon in the process d' --> pi + N + N is studied in the microscopic quark shell model and with a single-quark transition operator describing the transition q --> pi + q'. For the d' with quantum numbers…
We suggest a few particle physics processes in which excited 2p pionium $\mathrm{A}^\prime_{2\pi}$ may be observed. They include the $e^+e^-\to\pi^+\pi^-$ annihilation, the $V^0\to\pi^0\ell^+\ell^-$ and $K^\pm\to\pi^\pm\ell^+\ell^-$…
An upper limit on the branching ratio for the decay $K^+ \! \rightarrow \! \pi^+ \nu \overline{\nu}$ is set at $2.4 \times 10^{-9}$ at the 90\% C.L. using pions in the kinematic region $214~{\rm MeV}/c < P_\pi < 231~{\rm MeV}/c$. An upper…
Two aspects of isospin breaking in the decay $K^\pm \to \pi^0 \pi^0 e^\pm \stackrel{_{(-)}}{\nu_e}$ are studied and discussed. The first addresses the possible influence of the phenomenological description of the unitarity cusp on the…
An overview is presented about old and recent methods to compute the $K\to \pi \pi$ decay amplitude.
The decays of pions, the lightest particles composed of quarks, provide important insight into fundamental questions in particle physics including basic symmetries, the universality of fermionic weak interactions, and aspects of the strong…
We discuss the rescattering effects in decays $B\to \pi+K$. The picture we take is very simple: first, B decay into $K*\rho$, then $K*$ and $\rho$ go to kaon and pion by exchanging a pion. We find a up to ten percent CP violation asymmetry…
Experimental measurement of the probability of direct decay of a pion into a positron allows searching for interactions beyond the Standard Model: test of the hypothesis about the universality of the charged current,search for new…