We propose a non-perturbative method for computing the renormalization constants of generic composite operators. This method is intended to reduce some systematic errors, which are present when one tries to obtain physical predictions from the matrix elements of lattice operators. We also present the results of a calculation of the renormalization constants of several two-fermion operators, obtained, with our method, by numerical simulation of QCD, on a 16 3 × 32 lattice, at β = 6.0. The results of this simulation are encouraging, and further applications to four-fermion operators and to the heavy quark effective theory are proposed.

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We present a method to evaluate on the lattice the leading isospin breaking effects due to both the small mass difference between the up and down quarks and the QED interaction. Our proposal is applicable in principle to any QCD+QED gauge invariant hadronic observable which can be computed on the lattice. It is based on the expansion of the path-integral in powers of the small parameters (m d − mu)/ΛQCD andαem, wherem f is the renormalized quark mass andαem the renormalized fine structure constant. In this paper we discuss in detail the general strategy of the method and the conventional, although arbitrary, separation of QCD from QED isospin breaking corrections. We obtain results for the pion mass splitting, M (2)(3) and for the flavour symmetry breaking parameters R and Q. We also update our previous results for the QCD isospin breaking corrections to the K 2 decay rate and for the QCD contribution to the neutron-proton mass splitting.arXiv:1303.4896v1 [hep-lat]

Using the latest determinations of several theoretical and experimental parameters, we update the Unitarity Triangle analysis in the Standard Model. The basic experimental constraints come from the measurements of |V ub /V cb |, ∆m d , the lower limit on ∆m s , ε K , and the measurement of the phase of the B d -B d mixing amplitude through the time-dependent CP asymmetry in B 0 → J/ψK 0 decays. In addition, we consider the direct determination of α, γ, 2β+γ and cos 2β from the measurements of new CP-violating quantities, recently performed at the B factories. We also discuss the opportunities offered by improving the precision of the various physical quantities entering in the determination of the Unitarity Triangle parameters. The results and the plots presented in this paper can also be found at the URL http://www.utfit.org, where they are continuously updated with the newest experimental and theoretical results.

An upgraded analysis of ǫ, x d and ǫ ′ /ǫ, using the latest determinations of the relevant experimental and theoretical parameters, is presented. Using the recent determination of the top quark mass, m t = (174 ± 17) GeV, our best estimate is ǫ ′ /ǫ = 3.1 ± 2.5, which lies in the range given by E731. We describe our determination of ǫ ′ /ǫ and make a comparison with other similar studies. A detailed discussion of the matching of the full theory to the effective Hamiltonian, written in terms of lattice operators, is also given.

Froggatt-Nielsen mechanism in a model with SU(3)c×SU(3)L×U (1) Abstract: We update the constraints on new-physics contributions to ∆F = 2 processes from the generalized unitarity triangle analysis, including the most recent experimental developments. Based on these constraints, we derive upper bounds on the coefficients of the most general ∆F = 2 effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of new physics that contributes to these low-energy effective interactions. We point out that, due to the enhancement in the renormalization group evolution and in the matrix elements, the coefficients of non-standard operators are much more constrained than the coefficient of the operator present in the Standard Model. Therefore, the scale of new physics in models that generate new ∆F = 2 operators, such as next-to-minimal flavour violation, has to be much higher than the scale of minimal flavour violation, and it most probably lies beyond the reach of direct searches at the LHC.

We present a new calculation of the CP violation parameter ǫ ′ /ǫ. The results reported in this paper have been obtained by using the ∆S = 1 effective Hamiltonian computed at the next-to-leading order, including QCD and QED penguins. The matrix elements of the relevant operators have been taken from lattice QCD, at a scale µ = 2 GeV. At this relatively large scale, the perturbative matching between the relevant operators and the corresponding coefficients is quite reliable.The effect of the next-to-leading corrections is to lower the prediction obtained at the leading order, thus favouring the experimental result of E731. We analyze different contributions to the final result and compare the leading and next-to-leading cases.