In the past decade, one of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor. In this time frame, measurements and the theoretical interpretation of their results have advanced tremendously. A much broader understanding of flavor particles has been achieved; apart from their masses and quantum numbers, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. In the past, observations of CP violation were confined to neutral K mesons, but since the early 1990s, a large number of CP-violating processes have been studied in detail in neutral B mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of K, D, and B mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments; thus a review of the status of quark flavor physics is timely. This report is the result of the work of physicists attending the 5th CKM workshop, hosted by the University of Rome "La Sapienza", September 9-13, 2008. It summarizes the results of the current generation of experiments that are about to be completed and it confronts these results with the theoretical understanding of the field which has greatly improved in the past decade. (C) 2010 Elsevier B.V. All rights reserved

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.

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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.