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

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.

Midrapidity production of π ± , K ± , and (p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √ s NN = 5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum (p T) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0-90%. The comparison of the p T-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √ s NN = 2.76 TeV show no significant energy dependence. Blast-wave fits of the p T spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π , K/π) as a function of p T show pronounced maxima at p T ≈ 3 GeV/c in central Pb-Pb collisions. At high p T , particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √ s NN = 2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high p T and compatible with measurements at √ s NN = 2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.

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Beam asymmetry and differential cross-section for the reaction γp → ηp were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the η-meson, η → 2γ and η → 3π 0 , were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N (1670) was investigated and no evidence was found. PACS. 13.60.Le Meson production-13.88.+e Polarization in interactions and scattering-25.20.Lj Pho-toproduction reactions