Electromagnetic corrections in the anomaly sector

Chiral perturbation theory in the anomaly sector for $N_f=2$ is extended to include dynamical photons, thereby allowing a complete treatment of isospin breaking. A minimal set of independent chiral lagrangian terms is determined and the divergence structure is worked out. There are contributions from irreducible and also from reducible one-loop graphs, a feature of ChPT at order larger than four. The generating functional is non-anomalous at order $e^2p^4$, but not necessarily at higher order in $e^2$. Practical applications to $\gamma\pi\to\pi\pi$ and to the $\pi^0\to2\gamma$ amplitudes are considered. In the latter case, a complete discussion of the corrections beyond current algebra is presented including quark mass as well as electromagnetic effects.Comment: 26 pages, 3 figure

Four-point correlator constraints on electromagnetic chiral parameters and resonance effective lagrangians

We pursue the analysis of a set of generalized DGMLY sum rules for the electro-magnetic chiral parameters at order $e^{\mathrm{2}}p^{\mathrm{2}}$ and discuss implications for effective lagrangians with resonances. We exploit a formalism in which charge spurions are introduced and treated as sources. We show that no inconsistency arises from anomalies up to quadratic order in the spurions. We focus on the sum rules associated with QCD 4-point correlators which were not analyzed in detail before. Convergence properties of the sum rules are deduced from a general analysis of the form of the counterterms in the presence of electromagnetic spurions. Following the approach in which vector and axial-vector resonances are described with antisymmetric tensor fields and have a chiral order, we show that the convergence constraints are violated at chiral order four and can be satisfied by introducing a set of terms of order six. The relevant couplings get completely and uniquely determined from a set of generalized Weinberg sum-rule relations. An update on the corrections to Dashen's low-energy theorem is given

Four-point correlator constraints on electromagnetic chiral parameters and resonance effective lagrangians

We pursue the analysis of a set of generalized DGMLY sum rules for the electro-magnetic chiral parameters at order $e^{\mathrm{2}}p^{\mathrm{2}}$ and discuss implications for effective lagrangians with resonances. We exploit a formalism in which charge spurions are introduced and treated as sources. We show that no inconsistency arises from anomalies up to quadratic order in the spurions. We focus on the sum rules associated with QCD 4-point correlators which were not analyzed in detail before. Convergence properties of the sum rules are deduced from a general analysis of the form of the counterterms in the presence of electromagnetic spurions. Following the approach in which vector and axial-vector resonances are described with antisymmetric tensor fields and have a chiral order, we show that the convergence constraints are violated at chiral order four and can be satisfied by introducing a set of terms of order six. The relevant couplings get completely and uniquely determined from a set of generalized Weinberg sum-rule relations. An update on the corrections to Dashen's low-energy theorem is given

New physics in e⁺e⁻→Zγ with polarized beams

We present a complete description of angular distributions in the presence of new interactions for the process e⁺e⁻→Zγ with polarized beams at future linear colliders, by considering the most general form-factors allowed by gauge invariance. We include the possibility of CP violation, and classify the couplings according to their CP properties. Chirality conserving and chirality violating couplings give rise to distinct dependence on beam polarization. We present a comprehensive discussion including both types of couplings and provide a detailed comparison of the effects due to each. We discuss some selected asymmetries which would enable isolating effects of the CP-violating form-factors. We also present sensitivities on the corresponding couplings achievable at a future linear collider with realistic polarization and luminosity