A separable potential formalism is used to describe the ππ and KK interactions in the I G (J P C) = 0 + (0 ++) states in the energy range from the ππ threshold up to 1.4 GeV. Introduction of relativistic propaga-tors into a system of Lippmann-Schwinger equations leads to a very good description of the data (χ 2 = 0.93 per one degree of freedom). Three poles are found in this energy region: f 0 ...

We propose a non relativistic effective Lagrangian approach to study hadronic atom observables in the framework of QCD (including photons). We apply our formalism to derive a general expression for the width of the ππ atom decaying into two neutral pions. It contains all terms at leading and next-to-leading order in isospin breaking. The result allows one to evaluate the combination a0 − a2 of ...

We re-investigate the impact of isospin violation for extracting the s-wave ππ scattering phase shift difference δ 0 (M K) − δ 2 (M K) from K → ππ decays. Compared to our previous analysis in 2003, more precise experimental data and improved knowledge of low-energy constants are used. In addition, we employ a more robust data-driven method to obtain the phase shift difference δ 0

Mayer's second cluster integral for the pion gas is calculated in quantum mechanical approach. It is shown that nonresonant repulsive ππ-interactions as well as the finite width of resonances yield important but almost canceling contributions at typical chemical freeze-out temperatures of the hadron gas. The repulsive ππ-interactions to the second cluster integral is identified with Van der Waa...

We measure the CP -violating asymmetries in decays to the D → KK and D → ππ CP eigenstates using 540 fb of data collected with the Belle detector at or near the Υ(4S) resonance. Cabibbo-favored D → Kπ decays are used to correct for systematic detector effects. The results, A CP = (−0.43 ± 0.30 ± 0.11)% and A ππ CP = (+0.43± 0.52 ± 0.12)%, are consistent with no CP violation.

We have evaluated forward dispersion relations for scattering amplitudes that follow from direct fits to several sets of ππ scattering experiments, together with the precise K decay results, and high to energy data. We find that some of the most commonly used experimental sets, as well as some recent theoretical analyses based on Roy equations, do not satisfy these constraints by several standa...