The techniques of lattice gauge theory offer the possibility of accurate, non-perturbative calculation of the masses and matrix elements predicted by low-energy QCD. Of particular interest are the properties of the K-meson system and the lowenergy, weak matrix elements that are required to understand Kaon decays, especially those which enter the K → ππ amplitudes which violate CP symmetry. Pres...

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...

In the framework of heavy baryon chiral perturbation theory, we give the chiral expansion for the πN → ππN threshold amplitudes D1 and D2 to quadratic order in the pion mass. The theoretical results agree within one standard deviation with the empirical values. We also derive a relation between the two threshold amplitudes of the reaction πN → ππN and the ππ S–wave scattering lengths, a0 and a0...

Recent data from Belle show unusually large partial widths Υ(5S) → Υ(1S)ππ and Υ(5S) → Υ(2S)ππ. The Z(4430) narrow resonance also reported by Belle in ψπ spectrum has the properties expected of a c̄cud̄ charged isovector tetraquark T c̄c . The analogous state T b̄b in the bottom sector might mediate anomalously large cascade decays in the Upsilon system, Υ(mS) → T b̄b π → Υ(nS)ππ, with a tetraquark-...

Using 58 million J/ψ events taken with the BESII detector, a search for ηc CP violating decays into ππ and KK̄ has been performed. No clear ηc signal is observed, and upper limits for B(ηc → ππ) and B(ηc → KK̄) are given at the 90% confidence level, B(J/ψ → γηc) · B(ηc → π π) < 1.1 × 10, B(J/ψ → γηc) · B(ηc → π π) < 0.71 × 10, B(J/ψ → γηc) · B(ηc → K K) < 0.96 × 10 and B(J/ψ → γηc) ·B(ηc → K 0 SK...

The influence of strong and electroweak penguin amplitudes in B/B̄ → ππ is investigated in connection with the determination of the unitarity triangle angle α of the CKM matrix. A relation between the observable asymmetry, the angle α, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in B → ππ decays is only mildly influenced by t...

We have measured ππ and KK production in two-photon collisions using 87.7 fb of data collected with the Belle detector at the asymmetric energy ee collider KEKB. The cross sections are measured to high precision in the two-photon center-of-mass energy (W ) range between 2.4GeV < W < 4.1GeV and angular region |cos θ∗| < 0.6. The cross section ratio σ(γγ → KK)/σ(γγ → ππ) is measured to be 0.89 ± ...

We present fixed-t subtracted dispersion relations for Compton scattering off the nucleon at energies E γ ≤ 500 MeV, as a formalism to extract the nucleon polarizabilities with a minimum of model dependence. The subtracted dispersion integrals are mainly saturated by πN intermediate states in the s-channel γN → πN → γN and ππ intermediate states in the t-channel γγ → ππ → N ¯ N. For the subproc...

The relationship between the pionium lifetime and the ππ scattering lengths is established, including the sizable electromagnetic corrections. The bound state formalism that is used is that of constraint theory which provides a covariant three-dimensional reduction of the Bethe–Salpeter equation. The framework of generalized chiral perturbation theory allows then an analysis of the lifetime val...

We report on recent progress in studying two aspects of B physics, in which penguin amplitudes play an important role: 1. Bounds on penguin pollution in B(t) → ππ constraining CKM parameters, and a lower bound on B → ππ improving precision in sin 2α. 2. A suggestion for measuring the photon polarization in electroweak penguin decay, B → K1(1400)γ, providing a precision test of the Standard Model.