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We calculate form-factor ratios between the semileptonic decays {bar B}{sup 0} {yields} D{sup +} {ell}{sup -}{bar {nu}} and {bar B}{sub s}{sup 0} {yields} D{sub s}{sup +}{ell}{sup -}{bar {nu}} with lattice QCD. These ratios are a key theoretical input in a new strategy to determine the fragmentation fractions of the neutral B decays, which are needed for measurements of BR(B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -}). They use the MILC ensembles of gauge configurations with 2 + 1 flavors of sea quarks at two lattice spacings of approximately 0.12 fm and 0.09 fm. We use the model-independent z parametrization to extrapolate their simulation results at small recoil toward maximum recoil. The results for the form-factor ratios are {line_integral}{sub 0}{sup (s)} (M{sub {pi}}{sup 2})/{line_integral}{sub 0}{sup (d)} (M{sub K}{sup 2}) = 1.046(44){sub stat.}(15){sub syst.} and {line_integral}{sub 0}{sup (s)} (M{sub {pi}}{sup 2})/{line_integral}{sub 0}{sup (d)} (M{sub {pi}}{sup 2}) = 1.054(47){sub stat.}(17){sub syst.}. In contrast to a QCD sum-rule calculation, no significant departure from U-spin (d {leftrightarrow} s) symmetry is observed.

We fit lattice-QCD data for light-pseudoscalar masses and decay constants, from HISQ configurations generated by MILC, to SU(3) staggered chiral perturbation theory. At present such fits have rather high values of χ2/d.o.f., possibly due to the lack of ensembles with lighter-than-physical sea strange-quark masses. We propose solutions to this problem for future work. We also perform simple linear interpolations near the physical point on two ensembles with different lattice spacings, and obtain the preliminary result ( fK/ fπ) = 1.1872(41) in the continuum limit. XXIX International Symposium on Lattice Field Theory July 10 16 2011 Squaw Valley, Lake Tahoe, California

The semileptonic decay channel $B\ensuremath{\rightarrow}D\ensuremath{\tau}\ensuremath{\nu}$ is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently, the BABAR experiment reported the first observation of the exclusive semileptonic decay $B\ensuremath{\rightarrow}D{\ensuremath{\tau}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$, finding an approximately $2\ensuremath{\sigma}$ disagreement with the standard-model prediction for the ratio $R(D)=\mathrm{BR}(B\ensuremath{\rightarrow}D\ensuremath{\tau}\ensuremath{\nu})/\mathrm{BR}(B\ensuremath{\rightarrow}D\ensuremath{\ell}\ensuremath{\nu})$, where $\ensuremath{\ell}=e,\ensuremath{\mu}$. We compute this ratio of branching fractions using hadronic form factors computed in unquenched lattice QCD and obtain $R(D)=0.316(12)(7)$, where the errors are statistical and total systematic, respectively. This result is the first standard-model calculation of $R(D)$ from ab initio full QCD. Its error is smaller than that of previous estimates, primarily due to the reduced uncertainty in the scalar form factor ${f}_{0}({q}^{2})$. Our determination of $R(D)$ is approximately $1\ensuremath{\sigma}$ higher than previous estimates and, thus, reduces the tension with experiment. We also compute $R(D)$ in models with electrically charged scalar exchange, such as the type-II two-Higgs-doublet model. Once again, our result is consistent with, but approximately $1\ensuremath{\sigma}$ higher than, previous estimates for phenomenologically relevant values of the scalar coupling in the type-II model. As a by-product of our calculation, we also present the standard-model prediction for the longitudinal-polarization ratio ${P}_{L}(D)=0.325(4)(3)$.

We calculate the masses of bottom mesons using an improved relativistic action for the b-quarks and the RBC/UKQCD Iwasaki gauge configurations with 2+1 flavors of dynamical domain-wall light quarks. We analyze configurations with two lattice spacings: a^{-1} = 1.729 GeV (a ~ 0.11 fm) and a^{-1} = 2.281 GeV (a ~ 0.086 fm). We use an anisotropic, clover-improved Wilson action for the b-quark, and tune the three parameters of the action nonperturbatively such that they reproduce the experimental values of the B_s and B_s* heavy-light meson states. The masses and mass-splittings of the low-lying bottomonium states (such as the eta_b and Upsilon) can then be computed with no additional inputs, and comparison between these predictions and experiment provides a test of the validity of our method. We obtain bottomonium masses with total uncertainties of ~0.5-0.6% and fine-structure splittings with uncertainties of ~35-45%; for all cases we find good agreement with experiment. The parameters of the relativistic heavy-quark action tuned for b-quarks presented in this work can be used for precise calculations of weak matrix elements such as B-meson decay constants and mixing parameters with lattice discretization errors that are of the same size as in light pseudoscalar meson quantities. This general method can also be used for charmed meson masses and matrix elements if the parameters of the heavy-quark action are appropriately tuned., 30 pages, 14 figures, 14 tables

We calculate the leptonic decay constants of B_{(s)} and D_{(s)} mesons in lattice QCD using staggered light quarks and Fermilab bottom and charm quarks. We compute the heavy-light meson correlation functions on the MILC asqtad-improved staggered gauge configurations which include the effects of three light dynamical sea quarks. We simulate with several values of the light valence- and sea-quark masses (down to ~m_s/10) and at three lattice spacings (a ~ 0.15, 0.12, and 0.09 fm) and extrapolate to the physical up and down quark masses and the continuum using expressions derived in heavy-light meson staggered chiral perturbation theory. We renormalize the heavy-light axial current using a mostly nonperturbative method such that only a small correction to unity must be computed in lattice perturbation theory and higher-order terms are expected to be small. We obtain f_{B^+} = 196.9(8.9) MeV, f_{B_s} = 242.0(9.5) MeV, f_{D^+} = 218.9(11.3) MeV, f_{D_s} = 260.1(10.8) MeV, and the SU(3) flavor-breaking ratios f_{B_s}/f_{B} = 1.229(26) and f_{D_s}/f_{D} = 1.188(25), where the numbers in parentheses are the total statistical and systematic uncertainties added in quadrature.

We calculate form-factor ratios between the semileptonic decays ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$ and ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$ with lattice QCD. These ratios are a key theoretical input in a new strategy to determine the fragmentation fractions of neutral $B$ decays, which are needed for measurements of $\mathrm{BR}({B}_{s}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$. We use the MILC ensembles of gauge configurations with $2+1$ flavors of sea-quarks at two s of approximately 0.12 fm and 0.09 fm. We use the model-independent $z$ parametrization to extrapolate our simulation results at small recoil toward maximum recoil. Our results for the form-factor ratios are ${f}_{0}^{(s)}({M}_{\ensuremath{\pi}}^{2})/{f}_{0}^{(d)}({M}_{K}^{2})=1.046(44{)}_{\mathrm{stat}}(15{)}_{\mathrm{syst}}$ and ${f}_{0}^{(s)}({M}_{\ensuremath{\pi}}^{2})/{f}_{0}^{(d)}({M}_{\ensuremath{\pi}}^{2})=1.054(47{)}_{\mathrm{stat}}(17{)}_{\mathrm{syst}}$. In contrast to a QCD sum-rule calculation, no significant departure from $U$-spin ($d\ensuremath{\leftrightarrow}s$) symmetry is observed.

We calculate pseudoscalar masses on gauge configurations containing the effects of 2+1 flavors of dynamical asqtad quarks and quenched electromagnetism. The lattice spacings vary from 0.12 to 0.06 fm. The masses are fit with staggered chiral perturbation theory including NLO electromagnetic terms. We attempt to extract the fit parameters for the electromagnetic contributions, while taking into account the finite volume effects, and extrapolate them to the physical limit., Comment: 7 pages, 3 figures, 2 tables. Proceedings of the 30th International Symposium on Lattice Field Theory - Lattice 2012; June 24-29, 2012; Cairns, Australia. Expanded acknowledgements

We report on the status of our lattice-QCD calculation of the hadronic contribution to $B_d^0$ and $B^0_s$ mixing, with 2+1 flavors of dynamical sea quarks. Preliminary results for hadronic mixing matrix elements are given for a basis of five four-quark, dimension-six, $\Delta B=2$ mixing operators that spans the space of all possible hadronic mixing contributions in the Standard Model and beyond. At the intermediate stage of analysis reported on in this work, our errors are competitive with published Standard Model matrix element results. For beyond the Standard Model matrix elements, this is the first unquenched calculation and the first new lattice-QCD calculation in ten years., Comment: 13 pages, 6 figures. Proceedings of the XXIX International Symposium on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake Tahoe, California. Ver 2: New Figs. 2-4 and Table 4 corrects scripting error. Table 4 now includes results for BJU as well as BBGLN choice of evanescent operators

We give a brief overview and progress report on our lattice QCD calculation of neutral B mixing hadronic matrix elements needed for Standard Model and Beyond the Standard Model physics. Reference [1] contains more details and results., 3 pages, 0 figures, Proceedings of the 19th Particles and Nuclei International Conference (PANIC11), Cambridge, MA, U.S.A., July 2011

We report the non-perturbative tuning of parameters--- kappa_c, kappa_b, and kappa_crit ---that determine the heavy-quark mass in the Fermilab action. This requires the computation of the masses of Ds^(*) and Bs^(*) mesons comprised of a Fermilab heavy quark and a staggered light quark. Additionally, we report the hyperfine splittings for Ds and Bs mesons as a cross-check of our simulation and analysis methods. We find a splitting of 145 +/- 15 MeV for the Ds system and 40 +/- 9 MeV for the Bs system. These are in good agreement with the Particle Data Group average values of 143.9 +/- 0.4 MeV and 46.1 +/- 1.5 MeV, respectively. The calculations are carried out with the MILC 2+1 flavor gauge configurations at three lattice spacings $a$ approximately 0.15, 0.12, and 0.09 fm., 34 pages, 8 figures, 26 tables; some sections rearranged for clarity; conclusions unchanged; version accepted by Phys. Rev.D

We study the lattice spacing dependence, or scaling, of physical quantities using the highly improved staggered quark (HISQ) action introduced by the HPQCD/UKQCD Collaboration, comparing our results to similar simulations with the asqtad fermion action. Results are based on calculations with lattice spacings approximately 0.15, 0.12, and 0.09 fm, using four flavors of dynamical HISQ quarks. The strange and charm quark masses are near their physical values, and the light-quark mass is set to 0.2 times the strange-quark mass. We look at the lattice spacing dependence of hadron masses, pseudoscalar meson decay constants, and the topological susceptibility. In addition to the commonly used determination of the lattice spacing through the static quark potential, we examine a determination proposed by the HPQCD Collaboration that uses the decay constant of a fictitious ''unmixed ss'' pseudoscalar meson. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses.

We demonstrate a method for calculating the neutral B-meson decay constants and mixing matrix elements in unquenched lattice QCD with domain-wall light quarks and static b-quarks. Our computation is performed on the "2+1" flavor gauge configurations generated by the RBC and UKQCD Collaborations with a lattice spacing of a approx 0.11 fm (a^-1 = 1.729 GeV) and a lattice spatial volume of approximately (1.8 fm)^3. We simulate at three different light sea quark masses with pion masses down to approximately 430 MeV, and extrapolate to the physical quark masses using a phenomenologically-motivated fit function based on next-to-leading order heavy-light meson SU(2) chiral perturbation theory. For the b-quarks, we use an improved formulation of the Eichten-Hill action with static link-smearing to increase the signal-to-noise ratio. We also improve the heavy-light axial current used to compute the B-meson decay constant to O(alpha_s p a) using one-loop lattice perturbation theory. We present initial results for the SU(3)-breaking ratios f_{B_s}/f_{B_d} and xi = f_{B_s} sqrt{B_{B_s}}/f_{B_d} sqrt{B_{B_d}}, thereby demonstrating the viability of the method. For the ratio of decay constants, we find f_{B_s}/f_{B_d} = 1.15(12) and for the ratio of mixing matrix elements, we find xi = 1.13(12), where in both cases the errors reflect the combined statistical and systematic uncertainties, including an estimate of the size of neglected O(1/m_b) effects

We calculate the form factor ${f}_{+}({q}^{2})$ for $B$-meson semileptonic decay in unquenched lattice QCD with $2+1$ flavors of light sea quarks. We use Asqtad-improved staggered light quarks and a Fermilab bottom quark on gauge configurations generated by the MILC Collaboration. We simulate with several light-quark masses and at two lattice spacings, and extrapolate to the physical quark mass and continuum limit using heavy-light meson staggered chiral perturbation theory. We then fit the lattice result for ${f}_{+}({q}^{2})$ simultaneously with that measured by the BABAR experiment using a parameterization of the form-factor shape in ${q}^{2}$, which relies only on analyticity and unitarity in order to determine the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{\mathrm{ub}}|$. This approach reduces the total uncertainty in $|{V}_{\mathrm{ub}}|$ by combining the lattice and experimental information in an optimal, model-independent manner. We find a value of $|{V}_{\mathrm{ub}}|\ifmmode\times\else\texttimes\fi{}{10}^{3}=3.38\ifmmode\pm\else\textpm\fi{}0.36$.

We present the first lattice QCD calculation of the form factor for $\overline{B}\ensuremath{\rightarrow}{D}^{*}\ensuremath{\ell}\overline{\ensuremath{\nu}}$ with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC configurations), and the Fermilab action for the heavy quarks. The form factor is computed at zero recoil using a new double ratio method that yields the form factor more directly than the previous Fermilab method. Other improvements over the previous calculation include the use of much lighter light-quark masses, and the use of lattice (staggered) chiral perturbation theory in order to control the light-quark discretization errors and chiral extrapolation. We obtain for the form factor, ${\mathcal{F}}_{B\ensuremath{\rightarrow}{D}^{*}}(1)=0.921(13)(20)$, where the first error is statistical and the second is the sum of all systematic errors in quadrature. Applying a 0.7% electromagnetic correction and taking the latest PDG average for ${\mathcal{F}}_{B\ensuremath{\rightarrow}{D}^{*}}(1)|{V}_{cb}|$ leads to $|{V}_{cb}|=(38.7\ifmmode\pm\else\textpm\fi{}{0.9}_{\mathrm{exp} }\ifmmode\pm\else\textpm\fi{}{1.0}_{\mathrm{theo}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$.

Comparisons of lattice-QCD calculations of semileptonic form factors with experimental measurements often display two sets of points, one each for lattice QCD and experiment. Here we propose to display the output of a lattice-QCD analysis as a curve and error band. This is justified, because lattice-QCD results rely in part on fitting, both for the chiral extrapolation and to extend lattice-QCD data over the full physically allowed kinematic domain. To display an error band, correlations in the fit parameters must be taken into account. For the statistical error, the correlation comes from the fit. To illustrate how to address correlations in the systematic errors, we use the Becirevic-Kaidalov parametrization of the D -> pi l nu and D -> K l nu form factors, and a analyticity-based fit for the B -> pi l nu form factor f_+., 6 pp; v2 conforms with published version (one additional sentence and reference to clarify a point)

In the light pseudoscalar sector, we study rooted staggered chiral perturbation theory in the two-flavor case. The pion mass and decay constant are calculated through NLO for a partially-quenched theory. In the limit where the strange quark mass is large compared to the light quark masses and the taste splittings, we show that the SU(2) staggered chiral theory emerges from the SU(3) staggered chiral theory, as expected. Explicit relations between SU(2) and SU(3) low energy constants and taste-violating parameters are given. A brief summary of updated SU(2) chiral fits to the MILC lattice data is presented., Comment: 7 pages, talk given at the XXVIII International Symposium on Lattice Filed Theory, June 14-19,2010, Villasimius, Sardinia Italy

218 páginas, 106 figuras, 89 tablas.-- arXiv:0907.5386v2.-- Report of the CKM workshop, Rome 9-13th Sep. 2008.-- et al., One of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor and measurements and theoretical interpretations of their results have advanced tremendously: apart from masses and quantum numbers of flavor particles, 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. Till early 1990s observations of CP violation were confined to neutral $K$ mesons, but since then 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 summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field., We would like to thank the Universit´a ”Sapienza” of Rome and in particular its Department of Physics for the hospitality during the days of the workshop (9-13 September 2008). For the finantial and organizational support to the workshop itself we would like to thank INFN and in particular its Roma1 Section and the Local Organizing Committee (D. Anzellotti, C. Bulfon, G. Bucci, E. Di Silvestro, R. Faccini, M. Mancini, G. Piredda, and R. Soldatelli) respectively. The program of the workshop was elaborated by the Programm Committee (P. Ball, G. Cavoto, M. Ciuchini, R. Faccini – chair, R. Forty, S. Giagu, P. Gambino, B. Grinstein, S. Hashimoto, T. Iijima, G. Isidori, V. Luth, G. Piredda, M. Rescigno, and A. Stocchi) under consultation of the International Advisory Committee (I. I. Bigi, C. Bloise, A. Buras, N. Cabibbo, A. Ceccucci, P. Chang, F. Ferroni, A. Golutvin, A. Jawahery, A. S. Kronfeld, Y. Kwon, M. Mangano, W. J. Marciano, G. Martinelli, A. Masiero, T. Nakada, M. Neubert, P. Roudeau, A. I. Sanda, M. D. Shapiro, I. P.J. Shipsey, A. Soni, W. J. Taylor, N. G. Uraltsev, and M. Yamauchi). This work is supported by Australian Research Council and the Australian Department of Industry Innovation, Science and Research, the Natural Sciences and Engineering Research Council (Canada), the National Science Fundation of China, the Commissariat `a l’Energie Atomique and Institut National de Physique Nucl´eaire et de Physique des Particules (France), the Bundesministerium f¨ur Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Department of Science and Technology of India the Istituto Nazionale di Fisica Nucleare (Italy), the Ministry of Education Culture, Sports, Science, and Technology (Japan), the Japan Society of Promotion of Science, the BK21 program of the Ministry of Education of Korea, the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, the Slovenian Research Agency, Ministerio de Educaci´on y Ciencia (Spain), the Science and Technology Facilities Council (United Kingdom), and the US Department of Energy and National Science Foundation . Individuals have received support from European Community’s Marie-Curie Research Training Networks under contracts MRTN-CT-2006-035505 (‘Tools and Precision Calculations for Physics Discoveries at Colliders’) and MRTN-CT-2006-035482 (’FLAVIAnet’), from the National Science Fundation of China (grants 10735080 and 10625525), the DFG Cluster of Excellence ’Origin and Structure of the Universe’ (grant BU 706/2-1), the Jpan Society for the Promotion of Science (grant 20244037), and the A. von Humboldt Stiftung, from MICINN, Spain (grant FPA2007-60323), from the ITP at University of Zurich, from the US National Science Fundation (grant PHY-0555304) and Department of Energy (grants DE-FG02-96ER41005 and DE-AC02-07CH11359 – Fermi Research Alliance, LLC), and from Generalitat Valenciana (grant PROMETEO/2008/069).

=a, originally proposed bythe BMW collaboration, is computed using Symanzik flow at four lattice spacings ranging from0.15 to 0.06 fm. With a Taylor series ansatz, the results are simultaneously extrapolated to thecontinuum and interpolated to physical quark masses. We give a preliminary determination of thescale w