We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with N f = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their physical values. The simulations are based on a unitary setup for the two light quarks and on a mixed action approach for the strange and charm quarks. The analysis uses data at three values of the lattice spacing and pion masses in the range 210 ÷ 450 MeV, allowing for accurate continuum limit and controlled chiral extrapolation. The quark mass renormalization is carried out non-perturbatively using the RI -MOM method. The results for the quark masses converted to the MS scheme are: m ud (2 GeV) = 3.70(17) MeV, m s (2 GeV) = 99.6(4.3) MeV and m c (m c ) = 1.348(46) GeV. We obtain also the quark mass ratios m s /m ud = 26.66(32) and m c /m s = 11.62(16). By studying the mass splitting between the neutral and charged kaons and using available lattice results for the electromagnetic contributions, we evaluate m u /m d = 0.470(56), leading to m u = 2.36(24) MeV and m d = 5.03(26) MeV.

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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

In this paper, for the first time to our knowledge, a method is proposed to compute electromagnetic effects in hadronic processes, such as decays, using lattice simulations. The method can be applied, for example, to the leptonic and semileptonic decays of light or heavy pseudoscalar mesons. For these quantities the presence of infrared divergences in intermediate stages of the calculation makes the procedure much more complicated than is the case for the hadronic spectrum, for which calculations already exist. In order to compute the physical widths, diagrams with virtual photons must be combined with those corresponding to the emission of real photons. Only in this way do the infrared divergences cancel as first understood by Bloch and Nordsieck in 1937. We present a detailed analysis of the method for the leptonic decays of a pseudoscalar meson. The implementation of our method, although challenging, is within reach of the present lattice technology

We calculate the rates for the charged lepton flavour violating decays ℓ i → ℓ j γ, τ → ℓπ, τ → ℓη, τ → ℓη ′ , µ − → e − e + e − , the six three body leptonic decays τ − → ℓand the rate for µ − e conversion in nuclei in the Littlest Higgs model with T-parity (LHT). We also calculate the rates for K L,S → µe, K L,S → π 0 µe and B d,s → ℓ i ℓ j . We find that the relative effects of mirror leptons in these transitions are by many orders of magnitude larger than analogous mirror quark effects in rare K and B decays analyzed recently. In particular, in order to suppress the µ → eγ and µ − → e − e + e − decay rates and the µ − e conversion rate below the experimental upper bounds, the relevant mixing matrix in the mirror lepton sector V Hℓ must be rather hierarchical, unless the spectrum of mirror leptons is quasi-degenerate. We find that the pattern of the LFV branching ratios in the LHT model differs significantly from the one encountered in the MSSM, allowing in a transparent manner to distinguish these two models with the help of LFV processes. We also calculate (g −2) µ and find the new contributions to a µ below 1·10 −10 and consequently negligible. We compare our results with those present in the literature.

We present a lattice determination of the vector and scalar form factors of the D → π ν and D → K ν semileptonic decays, which are relevant for the extraction of the CKM matrix elements |V cd | and |V cs | from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with N f = 2 + 1 + 1 flavors of dynamical quarks, at three different values of the lattice spacing (a 0.062, 0.082, 0.089 fm) and with pion masses as small as 210 MeV. Quark momenta are injected on the lattice using non-periodic boundary conditions. The matrix elements of both vector and scalar currents are determined for a plenty of kinematical conditions in which parent and child mesons are either moving or at rest. Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum limit we determine the vector and scalar form factors in the whole kinematical region from q 2 = 0 up to q2 accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of q 2 where some deviations are visible. A set of synthetic data points, representing our results for f(q 2 ) for several selected values of q 2 , is provided and also the corresponding covariance matrix is available. At zero 4-momentum transfer we get: f

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We present a quenched lattice study of the form factors f + (q 2 ) and f 0 (q 2 ) of the matrix elements π|sγ µ u|K . We focus on the second-order SU(3)-breaking quantity [1 − f + (0)], which is necessary to extract |V us | from K ℓ3 decays. For this quantity we show that it is possible to reach the percent precision which is the required one for a significant determination of |V us |. The leading quenched chiral logarithms are corrected for by using analytic calculations in quenched chiral perturbation theory. Our final result, f K 0 π − + (0) = 0.960 ± 0.005 stat ± 0.007 syst , where the systematic error does not include the residual quenched effects, is in good agreement with the estimate made by Leutwyler and Roos. A comparison with other non-lattice computations and the impact of our result on the extraction of |V us | are also presented. a