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We present a lattice computation of the isospin-breaking corrections to pseudoscalar meson masses using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a∍0.062, 0.082, and 0.089 fm) with pion masses in the range Mp∍210 - 450MeV. The strange and charm quark masses are tuned at their physical values. We adopt the RM123 method based on the combined expansion of the path integral in powers of the d - and u -quark mass difference (md - mu) and of the electromagnetic coupling αem. Within the quenched QED approximation, which neglects the effects of the sea-quark charges, and after the extrapolations to the physical pion mass and to the continuum and infinite volume limits, we provide results for the pion, kaon, and (for the first time) charmed-meson mass splittings, for the prescription-dependent parameters επ0, εγ(MS, 2GeV), eK0 (MS, 2GeV), related to the violations of the Dashen's theorem, and for the light quark mass difference (md - mu) (MS, 2GeV). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present a lattice QCD calculation of the pseudoscalar decay constants fK, fD and fDs performed using the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 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 values in the real world. The simulations are based on a unitary setup for the two light mass-degenerate quarks and on a mixed action approach for the strange and charm quarks. We use data simulated at three different values of the lattice spacing in the range 0.06-0.09 fm and at pion masses in the range 210-450 MeV. Our main results are fK+/fπ+ = 1.184(16), fK+ = 154.4(2.0) MeV, which incorporate the leading strong isospin breaking correction due to the up and down quark mass difference, and fK = 155.0(1.9) MeV, fD = 207.4(3.8) MeV, fDs = 247.2(4.1) MeV, fDfD = 1.192(22) and (fDs/fD)/(fK/ fn) = 1.003(14) obtained in the isospin symmetric limit of QCD. Combined with the experimental measurements of the leptonic decay rates of kaon, pion, D and Ds mesons our results lead to the following determination of the Cabibbo-Kobayashi- Maskawa (CKM) matrix elements: |Vus| =0.2269(29), |Vcd| = 0.2221(67) and |V„| = 1.014(24). Using the latest value of |Vud| from superallowed nuclear ß decays the unitarity of the first row of the CKM matrix is fulfilled at the per mill level. [ABSTRACT FROM AUTHOR]

We present the first unquenched lattice QCD results for the bag parameters controlling the short distance contribution to D meson oscillations in the standard model and beyond. We have used the gauge configurations produced by the European Twisted Mass collaboration with Nƒ = 2 dynamical quarks, at four lattice spacings and light meson masses in the range 280-500 MeV. Renormalization is carried out nonperturbatively with the regularization-independent momentum subtraction method. The bag-parameter results have been used to constrain new physics effects in D0 - D0 mixing, to put a lower bound to the generic new physics scale and to constrain off-diagonal squark mass terms for TeV-scale supersymmetry. [ABSTRACT FROM AUTHOR]

Abstract: We present the summer 2012 update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. The increased accuracy on several of the fundamental constraints is now enhancing some of the tensions amongst and within the constraint themselves. In particular, the long standing tension between exclusive and inclusive determinations of the and CKM matrix elements is now playing a major role. Then we present the generalisation the UT analysis to investigate new physics (NP) effects, updating the constraints on NP contributions to processes. In the NP analysis, both CKM and NP parameters are fitted simultaneously to obtain the possible NP effects in any specific sector. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these low-energy effective interactions. [Copyright &y& Elsevier]

We present the update of the Unitarity Triangle analysis performed by the UT fit Collaboration within the Standard Model and beyond. Within the Standard Model, we find an overall consistency among the constraints, with some tension between the fit prediction and the experimental measurement of , and . Generalising the analysis beyond the Standard Model, we allow for New Physics effects in all processes simultanously. We obtain constraints on the parameters of the Cabibbo-Kobayashi-Maskawa matrix together with the New Physics ones. We find that a deviation from the Standard Model at the 3.1σ level in the mixing phase is confirmed by the present update, which includes the new DØ result on the dimuon charge asymmetry. However the new CDF measurement of is not included yet as the experimental likelihood is not publicly available. [ABSTRACT FROM AUTHOR]

We present the first lattice QCD estimate of the form factor , which is the key theoretical ingredient to extract from decays. Our result, , is in good agreement with the model estimate by Leutwyler and Roos and with the recent QCD sum rule estimate. After combining recent experimental results with our value for , we could verify the unitarity of the first row of the CKM matrix, namely . To make our estimate fully model independent we need to remove the quenched approximation and use ever lower quark masses (keeping, however, finite volume effects under control). [Copyright &y& Elsevier]

The results of a preliminary partially quenched () study of the light hadron spectrum, renormalization constants and light quark masses are presented. Numerical simulations are carried out with the LL-SSOR preconditioned Hybrid Monte Carlo with two degenerate dynamical fermions, using the plaquette gauge action and the Wilson quark action at . Finite volume effects have been investigated employing two lattice volumes: 163 ×48 and 243 ×48. Configurations have been generated at four values of the sea quark mass corresponding to . [Copyright &y& Elsevier]

We present the first lattice Nf=2+1+1 determination of the tensor form factor fDπ(K)T(q²) corresponding to the semileptonic D→π(K)ℓνℓ and rare D→π(K)ℓℓ decays as a function of the squared four-momentum transfer q². Together with our recent determination of the vector fDπ(K)+(q²) and scalar fDπ(K)0(q²) form factors, we complete the set of hadronic matrix elements regulating the semileptonic D→π(K)ℓνℓ and rare D→π(K)ℓℓ transitions within and beyond the standard model, when a nonzero tensor coupling is possible. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf=2+1+1 flavors of 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. We simulated at three different values of the lattice spacing and with pion masses as small as 220 MeV and with the valence heavy quark in the mass range from 0.7mphysc to 1.2mphysc. The matrix elements of the tensor current are determined for a plethora of kinematical conditions in which parent and child mesons are either moving or at rest. As in the case of the vector and scalar form factors, Lorentz symmetry breaking due to hypercubic effects is clearly observed also in the data for the tensor form factor 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 and infinite volume limits, we determine the tensor form factor in the whole kinematical region from q²=0 up to q²max=(MD-Mπ(K))2 accessible in the experiments. A set of synthetic data points, representing our results for fDπ(K)T(q²) for several selected values of q², is provided and the corresponding covariance matrix is also available. At zero four-momentum transfer, we get fDπT(0)=0.506 (79) and fDKT(0)=0.687 (54), which correspond to fDπT(0)/fDπ+(0)=0.827 (114) and fDKT(0)/fDK+(0)=0.898 (50). [ABSTRACT FROM AUTHOR]

We present a lattice determination of the vector and scalar form factors of the D→πℓν and D→Kℓν semileptonic decays, which are relevant for the extraction of the CKM matrix elements |Vcd| and |Vcs| from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 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 nonperiodic boundary conditions. The matrix elements of both vector and scalar currents are determined for 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 q² = 0 up to q² max = (MD-Mπ(K))² accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of q² where some deviations are visible. A set of synthetic data points, representing our results for fDπ(K)+(q²) and fDπ(K)0(q²) for several selected values of q², is provided and also the corresponding covariance matrix is available. At zero four-momentum transfer, we get fD→π+(0)=0.612(35) and fD→K+(0)=0.765(31). Using the experimental averages for |Vcd|fD→π+(0) and |Vcs|fD→K+(0), we extract |Vcd|=0.2330(137) and |Vcs|=0.945(38), respectively. The second row of the CKM matrix is found to be in agreement with unitarity within the current uncertainties: |Vcd|²+|Vcs|²+|Vcb|2=0.949(78). [ABSTRACT FROM AUTHOR]