We perform a dispersive theoretical study of the reaction γγ → ππ emphasizing the low energy region. The large source of theoretical uncertainty to calculate the γγ → ππ total cross section for √ s & 0.5 GeV within the dispersive approach is removed. This is accomplished by taking one more subtraction in the dispersion relations, where the extra subtraction constant is fixed by considering new ...

We perform a dispersive theoretical study of the reaction γγ → ππ emphasizing the low energy region. The large source of theoretical uncertainty to calculate the γγ → ππ total cross section for √ s & 0.5 GeV within the dispersive approach is removed. This is accomplished by taking one more subtraction in the dispersion relations, where the extra subtraction constant is fixed by considering new ...

The recent experimental data of both ππ/Kπ scattering and production processes, suggesting the existence of scalar σ and κ mesons, are reviewed. In many ππ/Kπ production processes the direct effects of their productions are observed, while they are, because of chiral symmetry, hidden in scattering processes, and now σ(500∼600) and κ(800∼900) are considered to be confirmed experimentally. The re...

We demonstrate that, together with the available experimental information , chiral symmetry determines the low energy behaviour of the ππ scattering amplitude to within very small uncertainties. In particular, the threshold parameters of the S–, P –, D– and F –waves are predicted, as well as the mass and width of the ρ and of the broad bump in the S–wave. The implications for the coupling const...

A portfolio of photochemical transformations found in a variety areas can be rationalized through consideration either gain 4nπ-electron aromaticity or relief (4n+2) π-electron antiaromaticity excited states ππ* character. These back-of-an-envelope tools provided by Baird's rule serve as compass for excursions electronically states. More information the Review H. Ottosson and co-workers (DOI: 1...

We present estimates of the charming penguin contribution to B → Kπ, ππ,Kη,Kη decays due to intermediate charmed meson states. We find that this contribution is indeed significant for B → Kπ decays, and its inclusion, together with the tree and penguin terms, produces large branching ratios in agreement with data, though the analysis is affected by large theoretical uncertainties. On the other ...

We discuss strategies to determine hadronic decay couplings from lattice studies. As an application, we explore the decay of a vector meson to two pseudoscalar mesons with Nf = 2 flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, we show how the transition rate can be evaluated from the amplitude for ρ→ ππ and from the annihilation component of ...

The σ resonance was observed as a conspicuous ππ peak in hadronic decays like J/ψ → ππω or D → πππ. The phase of the σ → ππ amplitude, extracted from production data within the conventional isobar model, is assumed to coincide with that in ππ elastic scattering. We check the validity of this assumption by using Lehmann-Symanzik-Zimmermann (LSZ) reduction and unitarity. The rescattering effects ...

The all–important consequence of Chiral Dynamics for ππ scattering is the Adler zero, which forces ππ amplitudes to grow asymptotically. The continuation of this subthreshold zero into the physical regions requires a P –wave resonance, to be identified with the ρ. It is a feature of ππ scattering that convergent dispersive integrals for the I = 1 channel are essentially saturated by the ρ–reson...