Investigation at a φ-factory can shed light on several debated issues in particle physics. We discuss: i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled kaon states, iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and η/η′ mesons, iv) the contribution to understand the nature of light scalar mesons, and v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the e + e − physics in the continuum with the measurements of (multi)hadronic cross sections and the study of γγ processes.

We have developed a phenomenological approach which describes very well the π 0 , η and η ′ meson production in the two-photon interactions. The simultaneous description of the π 0 , η and η ′ meson two-photon form factors is consistent with data in the space-like region. The obtained form factors are implemented in the event generator EKHARA and the simulated cross sections are presented. Uncertainties in the measured form factors coming from the model dependence in Monte Carlo simulations are studied. The model predictions for the form factor slopes at the origin are given and the high-Q 2 limit is also discussed.

We present EKHARA Monte Carlo event generator of reactions e + e − → e + e − π 0 and e + e − → e + e − π + π − . The newly added channel (e + e − → e + e − π 0 ) is important for γ * γ * physics and can be used for the pion transition form factor studies at meson factories.Keywords: Monte Carlo generator, Pion transition form factor, Pion pair production, Two-photon processes, e + e − annihilation and Empirical Models and Theories Nature of problem: PROGRAM SUMMARYThe first version of EKHARA [1,2] was developed to simulate background for the pion form factor measurement at meson factories coming from the process e + e − → e + e − π + π − . The newly added channel e + e − → e + e − π 0 will help in the pion transition from factor studies at meson factories [3]. Solution method:Events consisting of the momenta of the outgoing particles are generated by Monte Carlo methods. The generated events are distributed accordingly to the theoretical cross section. For the e + e − → e + e − π 0 mode the Monte Carlo sampling developed in [4] was adopted. Restrictions:In order to compile the code, the FORTRAN 77 compiler should support quadruple precision numbers. Unusual features:Calculations are carried in quadruple precision, in order to avoid numerical cancellations in e + e − → e + e − π + π − mode. Running time:Depends on the requested mode and applied kinematic cuts. Example: on Intel Core2 Quad CPU Q6600 @ 2.40GHz, using only one thread,• 10 5 unweighted e + e − π 0 events are generated in 78 seconds (no cuts),• 10 5 weighted e + e − π + π − events are generated in 38 seconds (with cuts [2]).

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A possibility of KLOE-2 experiment to measure the width Γ π 0 →γγ and the π 0 γγ * form factor F (Q 2 ) at low invariant masses of the virtual photon in the space-like region is considered. This measurement is an important test of the strong interaction dynamics at low energies. The feasibility is estimated on the basis of a Monte-Carlo simulation. The expected accuracy for Γ π 0 →γγ is at a per cent level, which is better than the current experimental world average and theory. The form factor will be measured for the first time at Q 2 ≤ 0.1 GeV 2 in the space-like region. The impact of these measurements on the accuracy of the pion-exchange contribution to the hadronic light-bylight scattering part of the anomalous magnetic moment of the muon is also discussed.

A model is developed for electromagnetic form factors of the charged and neutral K−mesons. The formalism is based on ChPT Lagrangians with vector mesons. The form factors, calculated without fitting parameters, are in a good agreement with experiment for space-like and time-like photon momenta. Contribution of the two-kaon channels to the muon anomalous magnetic moment a µ is calculated.

The features of the Resonance Chiral Theory (RχT) related to the description of the lightest scalar resonances, σ , f 0 (980) and a 0 (980), are discussed. Major attention is paid to the fits of the invariant mass distributions in the radiative decays of the φ (1020) meson (φ → (γa 0 →)γπη and φ → (γ f 0 /σ →)γππ). The study of the scalar sector in RχT is motivated by the success of the theory predictive power in numerous processes with other types of resonances. We conclude that RχT is sufficiently flexible to describe these decays, however the further quantitative improvement is required. The technical work-outs and related important questions are outlined.

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