Electrodynamics in the presence of an axion

The low energy limit of an axion field coupled to gauge fields is investigated through the behaviour of the gauge field propagator in a local vaccum angle background. The local (singular) part of the effective action for the axion field is calculated at one loop level. In the case of a timelike, linearly growing axion field, representing a massive axion, we give an asymptotic expansion of the causal propagator and we solve nonlocally for the first coefficient. We show that, for a generic axionic background, short distance propagation of the gauge fields is well defined.Comment: 13 page

Folding Froggatt-Nielsen into the Stueckelberg-Higgs mechanism in anomalous U(1) models

We describe a simple connection between the Froggatt-Nielsen, Stueckelberg and Higgs mechanisms, all three of them combined in a consistent way. This is illustrated in the context of a class of generalizations of the Standard Model with a gauge structure extended by a certain number of anomalous U(1) factors. These are built in the effective action in a way that gauge invariance and unitarity are preserved. Among other features, a physical axion with properties different from those of a Peccei-Quinn axion emerges.Comment: 9 pages, Based on talks presented at HEP2006, Recent Developments in High Energy Physics and Cosmology, The Annual Workshop of the Hellenic Society for the study of High Energy Physics, Ioannina, Greece, April 13-16, 2006. Some extra material include

Extra Quarks and Bileptons in BSM Physics in a 331331 Model

We describe some salient features of the $331_F$ (Frampton-Pisano-Pleitez) bilepton model, in which the constraints of anomaly cancelation require the number of generations to be three. In a class of six models, four of which characterised by a $\beta$ parameter describing the embedding of the hypercharge in the $SU(3)_L$ symmetry, a specific choice for $\beta$ allows bileptons in the spectrum, i.e. vectors and scalars of lepton numbers $\pm 2$. At the same time the model allows exotic quarks, with the third quark generation treated asymmetrically respect to the other two. Bileptons generate specific signatures in the form of multilepton final states in Drell-Yan like processes, with and without associated jets, which can be searched for at the LHC.Comment: 7 pages, 2 Figures. Proceedings of the Workshop QCD@work 2018, 25-28 June 2018, Matera, Ital

Deeply Virtual Neutrino Scattering at Leading Twist

We illustrate the generalization of results concerning exclusive electromagnetic processes in the deeply virtual limit (DVCS) to the case of the weak interactions.We briefly describe the derivation of the differential cross section for neutrino-nucleon reactions mediated by the neutral current and the amplitude for similar reactions mediated by the charged currents.Comment: 3 pages, 3 figures, Talk Presented at Neutrino Oscillations Workshop (NOW 2006), Otranto, Lecce, Italy, September 9-16 200

Polarized Double Photon Production in QCD to Order αs\alpha_s

We present a complete order $\alpha_s$ analysis of the process $p p\to \gamma \gamma + X$ with polarized initial states, previously studied by us with leading order structure functions. We include in our calculation new sets of parton densities evolved in NLO QCD, such as those of Gehrmann and Stirling and of Gl\"{u}ck et al., which incorporate the new anomalous dimensions of Mertig and Van Neerven in the evolution equation. A detailed phenomenological analysis is also given which includes the photon isolation. Our results indicate that the asymmetries, although not very large, should be substantial enough at RHIC energies to be measurable in future planned experiments.Comment: 29 pages revtex, 13 psfig

Exact Correlators from Conformal Ward Identities in Momentum Space and the Perturbative TJJTJJ Vertex

We present a general study of 3-point functions of conformal field theory in momentum space, following a reconstruction method for tensor correlators, based on the solution of the conformal Ward identities (CWI' s), introduced in recent works by Bzowski, McFadden and Skenderis (BMS). We investigate and detail the structure of the CWI's, their non-perturbative solutions and the transition to momentum space, comparing them to perturbation theory by taking QED as an example. We then proceed with an analysis of the $TJJ$ correlator, presenting independent and detailed re-derivations of the conformal equations in the reconstruction method of BMS, originally formulated using a minimal tensor basis in the transverse traceless sector. A careful comparison with a second basis introduced in previous studies shows that this correlator is affected by one anomaly pole in the graviton (T) line, induced by renormalization. The result shows that the origin of the anomaly, in this correlator, should be necessarily attributed to the exchange of a massless effective degree of freedom. Our results are then exemplified in massless QED at one-loop in $d$-dimensions, expressed in terms of perturbative master integrals. An independent analysis of the Fuchsian character of the solutions, which bypasses the 3K integrals, is also presented. We show that the combination of field theories at one-loop - with a specific field content of degenerate massless scalar and fermions - is sufficient to generate the complete non-perturbative solution, in agreement with a previous study in coordinate space. The result shows that free conformal field theories, in specific dimensions, arrested at one-loop, reproduce the general result for the $TJJ$. Analytical checks of this correspondence are presented in $d=3,4$ and $5$ spacetime dimensions[..].Comment: 79 pages, 3 Figures. Final version, with changes in section 8. Accepted for publication in Nuclear Physics

X-Events and Their Interpretation

We point out that when doubly-charged bileptons are pair produced at the LHC, kinematics dictate that they are both almost at rest in the lab frame and therefore their decays lead to final state muons in a characteristic X-shape with only very tiny track curvature because of the high muon energies. Such X-events have essentially no standard model background and provide a smoking gun for the 331 model.Comment: 5 pages LaTeX. Updated affiliatio