The branching ratios and CP asymmetries of B → ππ decays measured in B factory experiments indicate a large ratio of color-suppressed (C) to color-allowed (T ) tree contributions and a large relative phase between the tree and penguin amplitude. In this talk, I would like to report on a recent analysis to see whether the large C/T ratio can be explained within the QCD based model with i) a larg...

We present precise measurements of CP and CPT symmetry based on the full dataset of K → ππ decays collected by the KTeV experiment at FNAL. We measure the direct CP violation parameterRe(ǫ/ǫ) = (19.2 ±2.1) × 10. We find the KL-KS mass difference ∆m = (5265 ± 10)×10 6 h̄s and the KS lifetime τS = (89.62 ± 0.05)×10 s. We test CPT symmetry by finding the phase of the indirect CP violation parameter...

We review results of an analysis of ππ interactions in S, P and D waves for two-pion effective mass from threshold to about 1.4 GeV. In particular we show a recent improvement of this analysis above the KK̄ threshold using more data for phase shifts and including the S0 wave inelasticity from ππ → KK̄. In addition, we have improved the fit to the f2(1270) resonance and used a more flexible P wave...

Properties of the light scalar mesons face the experimental data on the φ → π 0 π 0 γ decay and the ππ scattering Abstract The high-statistical KLOE data on the φ → π 0 π 0 γ decay are described simultaneously with the data on ππ scattering and the ππ → K ¯ K reaction. The description is carried out taking into account the chiral shielding of the putative σ(600) meson and it's mixing with the w...

The low-energy ππ amplitude is computed explicitly to two-loop accuracy in the chiral expansion. It depends only on six independent (combinations of) low-energy constants which are not fixed by chiral symmetry. Four of these constants are determined via sum rules which are evaluated using ππ scattering data at higher energies. Dependence of the low-energy phase shifts and of the threshold param...

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...

We investigate the structure of the scalar mesons f0(975) and a0(980) within realistic meson-exchange models of the ππ and πη interactions. Starting from a modified version of the Jülich model for ππ scattering we perform an analysis of the pole structure of the resulting scattering amplitude and find, in contrast to existing models, a somewhat large mass for the f0(975) (mf0 = 1015 MeV, Γf0 = ...

The production and decay of vector mesons (ρ, ω) in pA reactions at COSY energies is studied with particular emphasis on their in-medium spectral functions. It is explored within transport calculations, if hadronic in-medium decays like ππ or πγ might provide complementary information to their dilepton (ee) decays. Whereas the ππ signal from the ρ-meson is found to be strongly distorted by pion...

We present a method to measure the CKM phase α and the tree and penguin (strong and electroweak) amplitudes in B → ππ decays, based on isospin consideration and the weak assumption that all tree amplitudes have a common strong phase and all penguin amplitudes have a different common phase. The method needs only the time-independent measurements of the relevant decay rates in B → ππ. We also pro...

The study of ππ scattering is a classical subject in the field of strong interactions: it is a scattering process that may occur at very low energy, far away from the resonance region, and it only involves the quasi–Goldstone bosons of the chiral symmetry of strong interactions. If we stay at low energy, we could expect its dynamics to be strongly constrained by chiral symmetry: as Weinberg sho...