The general structure of the cross section of γN scattering with polarized photon and/or nucleon in initial and/or final state is systematically described and exposed through invariant amplitudes. A low-energy expansion of the cross section up to and including the order O(ω 4 ) is given which involves ten structure parameters of the nucleon (dipole, quadrupole, dispersion, and spin polarizabilities). Their physical meaning is discussed in detail.Using fixed-t dispersion relations, predictions for these parameters are obtained and compared with results of chiral perturbation theory. It is emphasized that Compton scattering experiments at large angles can fix the most uncertain of these structure parameters. Predictions for the cross section and double-polarization asymmetries are given and the convergence of the expansion is investigated. The feasibility of the experimental determination of some of the structure parameters is discussed.

The Virgo Experiment is a gravitational wave interferometric detector. It consists in a Michelson interferometer with two 3 km long Fabry‐Perot cavities as orthogonal arms. The installation of the detector has been completed in September 2003 and presently the apparatus is under commissioning. In this article an overview of the detector status is presented

Photon-photon interactions have been studied at the ϕ-factory DAΦNE with the detector KLOE operating the machine at [Formula: see text] GeV, without tagging of the final leptons. The results about the γγ → η process and the evidence for γγ → π0π0 production at low π0π0 invariant mass are reviewed. The process γγ → π0 will be studied at KLOE-2 running the machine at ϕ-peak thanks to new lepton tagger detectors. In particular, the possibility to measure the two-photon width of π0 and the π0γ*γ transition form factor in the low (space-like) Q2 region is considered.

This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms. JINST 7 P03012In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency.This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper.

We present a new limit on the production of a light dark-force mediator with the KLOE detector at DANE. This boson, called U, has been searched for in the decay φ → ηU, U → e+e−, analyzing the decay η → π0π0π0 in a data sample of 1.7 fb−1. No structures are observed in the e+e− invariant mass distribution over the background. This search is combined with a previous result obtained from the decay η → π + π − π 0 , increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of α′/α < 1.7 × 10−5 for 30 < MU < 400 MeV and α′/α 8 × 10−6 for the sub-region 50 < MU < 210 MeV. This result assumes the Vector Meson Dominance expectations for the φηγ∗ transition form factor. The dependence of this limit on the transition form factor has also been studied

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.

The existence of a light dark force mediator has been tested with the KLOE detector at DAΦNE. This particle, called U , is searched for using the decay chain φ → η U , η → π + π − π 0 , U → e + e − . No evidence is found in 1.5 fb −1 of data. The resulting exclusion plot covers the mass range 5 < M U < 470 MeV, setting an upper limit on the ratio between the U boson coupling constant and the fine structure constant, α ′ /α, of ≤ 2 × 10 −5 at 90% C.L. for 50 < M U < 420 MeV.

There are no reasons why the energy spectra of the relic gravitons amplified by the pumping action of the background geometry should not increase at high frequencies. A typical example of this behavior are quintessential inflationary models where the slopes of the energy spectra can be either blue or mildly violet. In comparing the predictions of scenarios leading to blue and violet graviton spectra we face the problem of correctly deriving the sensitivities of the interferometric detectors. Indeed the expression of the signal-to-noise ratio not only depends upon the noise power spectra of the detectors but also upon the spectral form of the signal and, therefore, one can reasonably expect that models with different spectral behaviors will produce different signal-to-noise ratios. By assuming monotonic (blue) spectra of relic gravitons we will give general expressions for the signal-to-noise ratio in this class of models. As an example we studied the case of quintessential gravitons. The minimum achievable sensitivity to h 2 0 ΩGW of different pairs of detectors is computed, and compared with the theoretical expectations.