The role of pion rescattering in ππ decay of radially excited heavy quarkonia modeled in terms of a Qππ coupling, is investigated within the framework of the covariant Blankenbecler-Sugar equation. The effects of pion rescattering (or pion exchange) are shown to be large, unless the coupling of the two-pion system to the heavy quarks is mediated by a fairly light scalar σ meson, which couples t...

In production processes, e.g. J/Ψ → ωππ or p̄p → 3π, the σ and f0(980) overlap in the same partial wave. The conjecture of Extended Unitarity (EU) states that the ππ pair should have the same phase variation as ππ elastic scattering. This is an extension of Watson’s theorem beyond its original derivation, which stated only that the s-dependence of a single resonance should be universal. The pred...

We investigate the two-body decay modes ρρ, ππ∗(1300) and σσ of the f0(1500), all leading to the 4π decay channel, in a three-state mixing scheme, where the f0(1500) is a mixture of the lowest-lying scalar glueball with the nearby isoscalar states of the 0++ QQ̄ nonet. In the leading order of this scheme, the decay mechanism of the f0(1500) proceeds dominantly via its quarkonia components, which...

Extended analysis of the " penguin " part of K → ππ amplitude Abstract We make an attempt to clarify the role of the annihilation or " penguin " mode in the description of the K → ππ decay within the Standard Model. The attention is concentrated on new operators in the effective ∆S = 1 Hamiltonian and the violation of factorization for mesonic matrix elements of the local four-quark operators. ...

B decays into ππK and KKK, where the ππ and KK pairs interact in isospin zero S-wave, are studied in the ππ effective mass range from threshold to 1.2 GeV. The interplay of strong and weak decay amplitudes is analyzed using an unitary ππ and KK coupled channel model. Final state interactions are described in terms of four scalar form factors constrained by unitarity and chiral perturbation theo...

The influence of the hadronic ππ interaction on the wave functions of pionium (the Coulomb bound π+π− system) at distances ≤ 10 fm is calculated for s-states with principal quantum numbers n ≤ 4. Hadronic ππ potentials are used that reproduce the scattering phase shifts of two-loop chiral perturbation theory. The pionium wave functions ψn(r) are obtained by integrating the coupled Schrödinger e...

We study s-wave pion-pion (ππ) scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV. In the “Asqtad” improved staggered fermion formulation, we calculate the ππ four-point functions for isospin I = 0 and 2 channels, and use chiral perturbation theory at next-to-leading order to extrapolate our simulation results. Extrapolating to the physical pion mass gives the scat...

We discuss a possibility of large electroweak (EW) penguin contribution in B → Kπ and ππ. The recent experimental data may be still suggesting that there are some discrepancies between the data and theoretical estimations. In B → Kπ decays, to explain several theoretical relations among the branching ratios, a slightly large electroweak penguin contribution and large strong phase differences or...