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2.0

Jun 30, 2018
06/18

Jun 30, 2018
by
A. Bazavov; Tanmoy Bhattacharya; C. DeTar; H. -T. Ding; Steven Gottlieb; Rajan Gupta; P. Hegde; U. M. Heller; F. Karsch; E. Laermann; L. Levkova; Swagato Mukherjee; P. Petreczky; C. Schmidt; C. Schroeder; R. A. Soltz; W. Soeldner; R. Sugar; M. Wagner; P. Vranas

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We present results for the equation of state in (2+1)-flavor QCD using the highly improved staggered quark action and lattices with temporal extent $N_{\tau}=6,~8,~10$, and $12$. We show that these data can be reliably extrapolated to the continuum limit and obtain a number of thermodynamic quantities and the speed of sound in the temperature range $(130-400)$ MeV. We compare our results with previous calculations, and provide an analytic parameterization of the pressure, from which other...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice, Nuclear Theory

Source: http://arxiv.org/abs/1407.6387

3
3.0

Jun 30, 2018
06/18

Jun 30, 2018
by
A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; D. Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Kim; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou

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We compute the leptonic decay constants $f_{D^+}$, $f_{D_s}$, and $f_{K^+}$, and the quark-mass ratios $m_c/m_s$ and $m_s/m_l$ in unquenched lattice QCD using the experimentally determined value of $f_{\pi^+}$ for normalization. We use the MILC highly improved staggered quark (HISQ) ensembles with four dynamical quark flavors---up, down, strange, and charm---and with both physical and unphysical values of the light sea-quark masses. The use of physical pions removes the need for a chiral...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1407.3772

3
3.0

Jun 30, 2018
06/18

Jun 30, 2018
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; Si-Wei Qiu; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We compute the zero-recoil form factor for the semileptonic decay $\bar{B}^0\to D^{*+}\ell^-\bar{\nu}$ (and modes related by isospin and charge conjugation) using lattice QCD with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC \asqtad\ configurations), and the Fermilab action for the heavy quarks. Our calculations incorporate higher statistics, finer lattice spacings, and lighter quark masses than our 2008 work. As a byproduct of...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1403.0635

2
2.0

Jun 29, 2018
06/18

Jun 29, 2018
by
E. Gamiz; A. Bazavov; C. Bernard; C. DeTar; D. Du; A. X. El-Khadra; E. D. Freeland; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; P. B. Mackenzie; E. T. Neil; T. Primer; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We discuss the reduction of errors in the calculation of the form factor $f_+^{K \pi}(0)$ with HISQ fermions on the $N_f=2+1+1$ MILC configurations from increased statistics on some key ensembles, new data on ensembles with lattice spacings down to 0.042 fm and the study of finite-volume effects within staggered ChPT. We also study the implications for the unitarity of the CKM matrix in the first row and for current tensions with leptonic determinations of $\vert V_{us}\vert$.

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice, High Energy Physics - Experiment

Source: http://arxiv.org/abs/1611.04118

2
2.0

Jun 29, 2018
06/18

Jun 29, 2018
by
A. Bazavov; C. Bernard; C. M. Bouchard; C. C. Chang; C. DeTar; Daping Du; A. X. El-Khadra; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; A. S. Kronfeld; J. Laiho; P. B. Mackenzie; E. T. Neil; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We calculate---for the first time in three-flavor lattice QCD---the hadronic matrix elements of all five local operators that contribute to neutral $B^0$- and $B_s$-meson mixing in and beyond the Standard Model. We present a complete error budget for each matrix element and also provide the full set of correlations among the matrix elements. We also present the corresponding bag parameters and their correlations, as well as specific combinations of the mixing matrix elements that enter the...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1602.03560

11
11

Jun 28, 2018
06/18

Jun 28, 2018
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; R. D. Jain; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; Yuzhi Liu; P. B. Mackenzie; Y. Meurice; E. T. Neil; Si-Wei Qiu; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We compute the form factors for the $B \to Kl^+l^-$ semileptonic decay process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea quark, generated by the MILC Collaboration. The ensembles span lattice spacings from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the chiral extrapolation. The asqtad improved staggered action is used for the light valence and sea quarks, and the clover action with the Fermilab interpretation is used for the heavy $b$ quark. We...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1509.06235

10
10.0

Jun 28, 2018
06/18

Jun 28, 2018
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; A. S. Kronfeld; J. Laiho; L. Levkova; Yuzhi Liu; E. Lunghi; P. B. Mackenzie; Y. Meurice; E. Neil; Si-Wei Qiu; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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The rare decay $B\to\pi\ell^+\ell^-$ arises from $b\to d$ flavor-changing neutral currents and could be sensitive to physics beyond the Standard Model. Here, we present the first $ab$-$initio$ QCD calculation of the $B\to\pi$ tensor form factor $f_T$. Together with the vector and scalar form factors $f_+$ and $f_0$ from our companion work [J. A. Bailey $et~al.$, Phys. Rev. D 92, 014024 (2015)], these parameterize the hadronic contribution to $B\to\pi$ semileptonic decays in any extension of the...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1507.01618

5
5.0

Jun 27, 2018
06/18

Jun 27, 2018
by
Fermilab Lattice; MILC Collaborations; :; Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; Yuzhi Liu; P. B. Mackenzie; Y. Meurice; E. T. Neil; Si-Wei Qiu; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We present a lattice-QCD calculation of the $B\to\pi\ell\nu$ semileptonic form factors and a new determination of the CKM matrix element $|V_{ub}|$. We use the MILC asqtad 2+1-flavor lattice configurations at four lattice spacings and light-quark masses down to 1/20 of the physical strange-quark mass. We extrapolate the lattice form factors to the continuum using staggered chiral perturbation theory in the hard-pion and SU(2) limits. We employ a model-independent $z$ parameterization to...

Topics: High Energy Physics - Experiment, High Energy Physics - Phenomenology, High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.07839

8
8.0

Jun 27, 2018
06/18

Jun 27, 2018
by
Fermilab Lattice; MILC Collaborations; :; Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; Si-Wei Qiu; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay $\overline{B} \rightarrow D \ell \overline{\nu}$ at nonzero recoil. We carry out numerical simulations on fourteen ensembles of gauge-field configurations generated with 2+1 flavors of asqtad-improved staggered sea quarks. The ensembles encompass a wide range of lattice spacings (approximately 0.045 to 0.12 fm) and ratios of light (up and down) to strange sea-quark masses ranging from...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.07237

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32

Sep 24, 2013
09/13

Sep 24, 2013
by
E. T. Neil; Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; R. Jain; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; for the Fermilab Lattice Collaboration; for the MILC Collaboration

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We give an update on simulation results for the decay constants f_B, f_{B_s}, f_D and f_{D_s}. These decay constants are important for precision tests of the standard model, in particular entering as inputs to the global CKM unitarity triangle fit. The results presented here make use of the MILC (2+1)-flavor asqtad ensembles, with heavy quarks incorporated using the clover action with the Fermilab method. Partially quenched, staggered chiral perturbation theory is used to extract the decay...

Source: http://arxiv.org/abs/1112.3978v1

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53

Sep 23, 2013
09/13

Sep 23, 2013
by
A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; R. Jain; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; E. T. Neil; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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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...

Source: http://arxiv.org/abs/1112.3051v1

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31

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; Ph. de Forcrand; Steven Gottlieb; U. M. Heller; J. E. Hetrick; O. Jahn; L. Levkova; F. Maresca; D. B. Renner; R. Sugar; D. Toussaint

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We have extended our computation of the inverse participation ratio of low-lying (asqtad) Dirac eigenvectors in quenched SU(3). The scaling dimension of the confining manifold is clearer and very near 3. We have also computed the 2-point correlator which further characterizes the localization.

Source: http://arxiv.org/abs/hep-lat/0510025v1

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41

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; B. Billeter; C. DeTar; L. Levkova; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Osborn; D. B. Renner; D. Toussaint; R. Sugar

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We report new data for the topological susceptibility computed on 2+1 flavor dynamical configurations with lattice spacing 0.06 fm, generated with the asqtad action. The topological susceptibility is computed by HYP smearing and compared with rooted staggered chiral perturbation theory as the pion mass goes to zero. At 0.06 fm, the raw data is already quite close to the continuum extrapolated values obtained from coarser lattices. These results provide a further test of the asqtad action with...

Source: http://arxiv.org/abs/0710.3124v1

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89

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Levkova; R. Sugar; D. Toussaint

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We present results for the QCD equation of state, quark densities and susceptibilities at nonzero chemical potential, using 2+1 flavor asqtad ensembles with $N_t=4$. The ensembles lie on a trajectory of constant physics for which $m_{ud}\approx0.1m_s$. The calculation is performed using the Taylor expansion method with terms up to sixth order in $\mu/T$.

Source: http://arxiv.org/abs/0710.1330v4

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43

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; T. Burch; C. DeTar; L. Levkova; Steven Gottlieb; U. M. Heller; J. E. Hetrick; R. Sugar; D. Toussaint

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We present results for the QCD equation of state with nonzero chemical potential using the Taylor expansion method with terms up to sixth order in the expansion. Our calculations are performed on asqtad 2+1 quark flavor lattices at $N_t=4$.

Source: http://arxiv.org/abs/0710.2520v1

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35

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Levkova; J. Osborn; D. Renner; R. Sugar; D. Toussaint

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We discuss the current status of our calculation of the physics of pi and K mesons using three dynamical flavors of improved staggered quarks. This year, we have a new ensemble with a lattice spacing of 0.06 fm and a light sea mass of 0.2 m_s, as well as significant increases in statistics at several coarser lattice spacings and/or heavier sea masses. Results for decay constants, quark masses, low energy constants, condensates, and V_{us} are presented.

Source: http://arxiv.org/abs/0710.1118v2

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34

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Aubin; C. Bernard; C. DeTar; M. Di Pierro; A. El-Khadra; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Hetrick; A. S. Kronfeld; P. B. Mackenzie; D. Menscher; M. Nobes; M. Okamoto; M. B. Oktay; J. Osborn; J. Simone; R. Sugar; D. Toussaint; H. D. Trottier

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We present the first three-flavor lattice QCD calculations for $D\to \pi l\nu$ and $D\to K l\nu$ semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC collaboration. With an improved staggered action for light quarks, we are able to simulate at light quark masses down to 1/8 of the strange mass. Consequently, the systematic error from the chiral extrapolation is much smaller than in previous calculations with Wilson-type light quarks....

Source: http://arxiv.org/abs/hep-ph/0408306v1

51
51

Sep 23, 2013
09/13

Sep 23, 2013
by
A. Bazavov; C. Bernard; C. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; P. B. Mackenzie; M. B. Oktay; R. Sugar; D. Toussaint; R. S. Van de Water

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Dramatic progress has been made over the last decade in the numerical study of quantum chromodynamics (QCD) through the use of improved formulations of QCD on the lattice (improved actions), the development of new algorithms and the rapid increase in computing power available to lattice gauge theorists. In this article we describe simulations of full QCD using the improved staggered quark formalism, ``asqtad'' fermions. These simulations were carried out with two degenerate flavors of light...

Source: http://arxiv.org/abs/0903.3598v2

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42

Sep 23, 2013
09/13

Sep 23, 2013
by
A. Bazavov; T. Bhattacharya; M. Cheng; N. H. Christ; C. DeTar; S. Ejiri; Steven Gottlieb; R. Gupta; U. M. Heller; K. Huebner; C. Jung; F. Karsch; E. Laermann; L. Levkova; C. Miao; R. D. Mawhinney; P. Petreczky; C. Schmidt; R. A. Soltz; W. Soeldner; R. Sugar; D. Toussaint; P. Vranas

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We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent Nt=8. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two O(a^2) improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is...

Source: http://arxiv.org/abs/0903.4379v1

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59

Sep 23, 2013
09/13

Sep 23, 2013
by
A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; J. Osborn; R. Sugar; D. Toussaint

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We report on recent progress in employing the Highly Improved Staggered Quark (HISQ) action introduced by the HPQCD/UKQCD collaboration in simulations with dynamical fermions. The HISQ action is an order $a^2$ Symanzik-improved action with further suppressed taste symmetry violations. The improvement in taste symmetry is achieved by introducing Fat7 smearing of the original gauge links and reunitarization (projection to an element of U(3) or SU(3)) followed by Asq-type smearing. Major...

Source: http://arxiv.org/abs/0903.0874v1

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44

Sep 23, 2013
09/13

Sep 23, 2013
by
A. Bazavov; T. Bhattacharya; M. Cheng; C. DeTar; H. -T. Ding; Steven Gottlieb; R. Gupta; P. Hegde; U. M. Heller; F. Karsch; E. Laermann; L. Levkova; S. Mukherjee; P. Petreczky; C. Schmidt; R. A. Soltz; W. Soeldner; R. Sugar; D. Toussaint; W. Unger; P. Vranas

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We present results on the chiral and deconfinement properties of the QCD transition at finite temperature. Calculations are performed with 2+1 flavors of quarks using the p4, asqtad and HISQ/tree actions. Lattices with temporal extent N_tau=6, 8 and 12 are used to understand and control discretization errors and to reliably extrapolate estimates obtained at finite lattice spacings to the continuum limit. The chiral transition temperature is defined in terms of the phase transition in a theory...

Source: http://arxiv.org/abs/1111.1710v2

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42

Sep 23, 2013
09/13

Sep 23, 2013
by
MILC Collaboration; C. Bernard; T. DeGrand; C. DeTar; Steven Gottlieb; Urs M. Heller; J. E. Hetrick; N. Ishizuka; C. McNeile; R. Sugar; D. Toussaint; M. Wingate

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We report on the MILC collaboration's calculation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$, and their ratios. Our central values come from the quenched approximation, but the quenching error is estimated from $N_F=2$ dynamical staggered lattices. We use Wilson light valence quarks and Wilson and static heavy quarks. We find, for example, $f_B=157 \pm 11 {}^{+25}_{-9} {}^{+23}_{-0} \MeV$, $f_{B_s}/f_B = 1.11 \pm 0.02 {}^{+0.04}_{-0.03} \pm 0.03$, $f_{D_s} = 210 \pm 9 {}^{+25}_{-9} {}^{+17}_{-1}...

Source: http://arxiv.org/abs/hep-ph/9806412v2

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30

Sep 23, 2013
09/13

Sep 23, 2013
by
MILC Collaboration; A. Bazavov; C. Bernard; C. DeTar; X. Du; W. Freeman; Steven Gottlieb; Urs M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; M. B. Oktay; J. Osborn; R. Sugar; D. Toussaint; R. S. Van de Water

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We present the current status of the MILC collaboration's calculations of the properties of the light pseudoscalar meson sector. We use asqtad staggered ensembles with 2+1 dynamical flavors down to $a \approx 0.045$ fm and light quark mass down to 0.05 $m_s$. Here we describe fits to the data using chiral forms from SU(3) chiral perturbation theory, including all staggered taste violations at NLO and the continuum NNLO chiral logarithms. We emphasize issues of convergence of the chiral...

Source: http://arxiv.org/abs/1012.0868v1

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66

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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We present an update of our calculations of the decay constants of the D, D_s, B, and B_s mesons in unquenched 2+1 flavor QCD. We use the MILC library of improved staggered gauge ensembles at lattice spacings 0.09, 0.12, and 0.15 fm, clover heavy quarks with the Fermilab normalizations, and improved staggered light valence quarks.

Source: http://arxiv.org/abs/0904.1895v1

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48

Sep 23, 2013
09/13

Sep 23, 2013
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; Daping Du; A. X. El-Khadra; J. Foley; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; Jongjeong Kim; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; Y. Meurice; E. Neil; M. B. Oktay; Si-Wei Qiu; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou

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We calculate form-factor ratios between the semileptonic decays \bar{B}->D^+\ell^-\bar{\nu} and \bar{B}_s->D_s^+\ell^-\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^0_s-> \mu^+\mu^-). We 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...

Source: http://arxiv.org/abs/1202.6346v2

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46

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; P. Williams; S. Datta; Steven Gottlieb; C. DeTar; Urs M. Heller; C. McNeile; K. Orginos; R. Sugar; D. Toussaint

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We compute the leptonic decay constants of heavy-light vector mesons in the quenched approximation. The reliability of lattice computations for heavy quarks is checked by comparing the ratio of vector to pseudoscalar decay constant with the prediction of Heavy Quark Effective Theory in the limit of infinitely heavy quark mass. Good agreement is found. We then calculate the decay constant ratio for B mesons: $f_{B^*}/f_B= 1.01(0.01)(^{+0.04}_{-0.01})$. We also quote quenched $f_{B^*}=177(6)(17)$...

Source: http://arxiv.org/abs/hep-lat/0109015v2

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36

Sep 23, 2013
09/13

Sep 23, 2013
by
The MILC Collaboration; C. Bernard; T. Blum; T. DeGrand; C. DeTar; Steven Gottlieb; U. M. Heller; J. Hetrick; C. McNeile; K. Rummukainen; A. Soni; R. Sugar; D. Toussaint; M. Wingate

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We describe the current status of the MILC collaboration computation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios. Progress over the past year includes: better statistics and plateaus at $\beta=6.52$ (quenched), $\beta=5.6$ ($N_F=2$) and $\beta=5.445$ ($N_F=2$), new runs with a wide range of dynamical quark masses at $\beta=5.5$ ($N_F=2$), an estimate of the systematic errors due to the chiral extrapolation, and an improved analysis which consistently takes into account both the...

Source: http://arxiv.org/abs/hep-lat/9608092v1

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42

Sep 23, 2013
09/13

Sep 23, 2013
by
K. Orginos; R. Sugar; D. Toussaint

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We study improved Kogut-Susskind fermion actions focusing on flavor symmetry restoration. Several variants of fat actions suitable for dynamical simulations are considered, including an action with no tree level order a-squared errors. The spectrum of all the pions is computed and used as a measure of flavor symmetry violation. Finally, the Naik term is introduced to restore rotational symmetry.

Source: http://arxiv.org/abs/hep-lat/9909087v1

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Sep 22, 2013
09/13

Sep 22, 2013
by
M. Okamoto; C. Aubin; C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Hetrick; A. S. Kronfeld; P. B. Mackenzie; D. P. Menscher; M. Nobes; M. B. Oktay; J. Osborn; J. N. Simone; R. Sugar; D. Toussaint; H. D. Trottier

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We present results for form factors of semileptonic decays of $D$ and $B$ mesons in 2+1 flavor lattice QCD using the MILC gauge configurations. With an improved staggered action for light quarks, we successfully reduce the systematic error from the chiral extrapolation. The results for $D$ decays are in agreement with experimental ones. The results for B decays are preliminary. Combining our results with experimental branching ratios, we then obtain the CKM matrix elements $|V_{cd}|$,...

Source: http://arxiv.org/abs/hep-lat/0409116v1

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Sep 22, 2013
09/13

Sep 22, 2013
by
C. Bernard; C. DeTar; Steven Gottlieb; E. Gregory; Urs Heller; C. McNeile; J. Osborn; R. Sugar; D. Toussaint

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We present preliminary results of a determination of the semileptonic form factor for the decay of pseudoscalar heavy-light mesons to pseudoscalar light-light mesons in full QCD. In this preliminary study we focus on the effects of dynamical quark loops. Accordingly, we compare results of simulations with matched quenched and Asqtad dynamical gauge configurations. The latter include three flavors of light quarks. Our simulation uses clover Wilson valence quarks, treated in the Fermilab...

Source: http://arxiv.org/abs/hep-lat/0309055v1

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39

Sep 22, 2013
09/13

Sep 22, 2013
by
MILC Collaboration; C. Aubin; C. Bernard; C. DeTar; Steven Gottlieb; E. B. Gregory; Urs M. Heller; J. E. Hetrick; J. Osborn; R. Sugar; D. Toussaint

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We compute pseudoscalar meson masses and decay constants using staggered quarks on lattices with three flavors of sea quarks and lattice spacings $\approx 0.12$ fm and $\approx 0.09$ fm. We fit partially quenched results to ``staggered chiral perturbation theory'' formulae, thereby taking into account the effects of taste-symmetry violations. Chiral logarithms are observed. From the fits we calculate $f_\pi$ and $f_K$, extract Gasser-Leutwyler parameters of the chiral Lagrangian, and (modulo...

Source: http://arxiv.org/abs/hep-lat/0309088v1

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Sep 22, 2013
09/13

Sep 22, 2013
by
MILC Collaboration; C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Osborn; R. Sugar; D. Toussaint

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We report on preliminary results from multi-particle fits to meson propagators with three flavors of light dynamical quarks. We are able to measure excited states in propagators with pion quantum numbers, which we interpret as the pion 2S state, and is evidence of locality of the action. In the a_0 (0^{++}) propagators we find evidence for excited states which are probably the expected decay channels, pi+eta and K+Kbar.

Source: http://arxiv.org/abs/hep-lat/0309117v1

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44

Sep 22, 2013
09/13

Sep 22, 2013
by
Jon A. Bailey; C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. Okamoto; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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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...

Source: http://arxiv.org/abs/0811.3640v3

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Sep 22, 2013
09/13

Sep 22, 2013
by
C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. Okamoto; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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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...

Source: http://arxiv.org/abs/0906.2498v2

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Sep 22, 2013
09/13

Sep 22, 2013
by
MILC Collaboration; Claude Bernard; Tom Blum; Carleton DeTar; Steven Gottlieb; Urs M. Heller; James E. Hetrick; Craig McNeile; K. Rummukainen; R. Sugar; D. Toussaint

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We calculate the light quark spectrum of lattice QCD in the quenched approximation using Kogut-Susskind quarks. By combining results for different lattice spacings, several volumes and five quark masses, we are able to take the light quark mass, infinite volume, continuum limit. When we use non-linear chiral extrapolations, we find that the nucleon to rho mass ratio is 1.254 +- 0.018 +- 0.027, where the errors are statistical and systematic (within the quenched approximation), respectively....

Source: http://arxiv.org/abs/hep-lat/9805004v2

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Sep 22, 2013
09/13

Sep 22, 2013
by
S. Basak; A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; J. Osborn; R. Sugar; D. Toussaint

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We present our initial study of the electromagnetic splittings of charged and neutral mesons, and the violation of Dashen's theorem. Hadron masses are calculated on MILC N_f=2+1 QCD ensembles at lattice spacing \approx 0.15fm, together with quenched non-compact U(1) configurations. The O(a^2) tadpole improved staggered quark (asqtad) action is used both for the sea quarks and for six different valence quark masses. Chiral extrapolations are performed using partially quenched chiral perturbation...

Source: http://arxiv.org/abs/0812.4486v1

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Sep 22, 2013
09/13

Sep 22, 2013
by
C. Bernard; T. DeGrand; C. DeTar; Steven Gottlieb; E. Gregory; A. Hart; A. Hasenfratz; Urs Heller; J. Hetrick; J. Osborn; R. Sugar; D. Toussaint

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Chiral perturbation theory predicts that in quantum chromodymamics light dynamical quarks suppress the topological (instanton) susceptibility. We investigate this suppression through direct numerical simulation using the Asqtad improved lattice fermion action. This action holds promise for carrying out nonperturbative simulations over a range of quark masses for which chiral perturbation theory is expected to converge. To test the effectiveness of the action in capturing instanton physics, we...

Source: http://arxiv.org/abs/hep-lat/0308019v2

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44

Sep 22, 2013
09/13

Sep 22, 2013
by
C. Bernard; S. Datta; C. DeTar; S. Gottlieb; U. M. Heller; J. Hetrick; C. Mcneile; K. Orginos; R. Sugar; D. Toussaint

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We present results for pseudoscalar decay constants of heavy-light mesons using both quenched and N_f = 2 dynamical fermion configurations. A variety of fermion actions is investigated : Wilson, nonperturbative clover, and fat-link clover. For heavy quarks the Fermilab formalism is applied. In the quenched approximation, results with the nonperturbatively improved clover action of the Alpha collaboration allow us to study the systematic error of the continuum extrapolation from the Wilson...

Source: http://arxiv.org/abs/hep-lat/0011029v1

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Sep 22, 2013
09/13

Sep 22, 2013
by
The MILC Collaboration; C. Bernard; T. Blum; A. De; T. DeGrand; C. DeTar; Steven Gottlieb; Urs M. Heller; N. Ishizuka; L. Kärkkäinen; J. Labrenz; K. Rummukainen; A. Soni; R. Sugar; D. Toussaint

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Preliminary results from the MILC collaboration for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios are presented. We compute in the quenched approximation at $\beta=6.3$, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify all systematic errors other than quenching, and have a first indication of the size of quenching errors.

Source: http://arxiv.org/abs/hep-ph/9503336v1

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Sep 21, 2013
09/13

Sep 21, 2013
by
C. Aubin; C. Bernard; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. E. Hetrick; J. Osborn; R. Sugar; D. Toussaint

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We have extended our program of QCD simulations with an improved Kogut-Susskind quark action to a smaller lattice spacing, approximately 0.09 fm. Also, the simulations with a approximately 0.12 fm have been extended to smaller quark masses. In this paper we describe the new simulations and computations of the static quark potential and light hadron spectrum. These results give information about the remaining dependences on the lattice spacing. We examine the dependence of computed quantities on...

Source: http://arxiv.org/abs/hep-lat/0402030v1

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29

Sep 21, 2013
09/13

Sep 21, 2013
by
C. Bernard; T. Blum; T. DeGrand; C. Detar; S. Gottlieb; A. Krasnitz; R. Sugar; D. Toussaint

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We have carried out spectrum calculations with two flavors of dynamical Kogut-Susskind quarks on four lattice sizes from $8^3\times 24$ to $16^3\times24$ at couplings that correspond to chiral symmetry restoration for a lattice with 6 time slices. We estimate that the linear spatial sizes of the lattices range from 1.8 to 3.6 fm. We find significant finite size effects for all particles between the smallest and largest volume with the larger quark mass that we study, $am_q=0.025$, where $a$ is...

Source: http://arxiv.org/abs/hep-lat/9305023v1

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43

Sep 21, 2013
09/13

Sep 21, 2013
by
MILC Collaboration; C. Aubin; C. Bernard; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. E. Hetrick; J. Osborn; R. Sugar; D. Toussaint

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As part of our program of lattice simulations of three flavor QCD with improved staggered quarks, we have calculated pseudoscalar meson masses and decay constants for a range of valence quark masses and sea quark masses on lattices with lattice spacings of about 0.125 fm and 0.09 fm. We fit the lattice data to forms computed with staggered chiral perturbation theory. Our results provide a sensitive test of the lattice simulations, and especially of the chiral behavior, including the effects of...

Source: http://arxiv.org/abs/hep-lat/0407028v3

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39

Sep 21, 2013
09/13

Sep 21, 2013
by
C. Bernard; C. DeTar; M. Di Pierro; A. X. El-Khadra; R. T. Evans; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. Okamoto; J. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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We present the first lattice QCD calculation of the form factor for B-> D* l 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...

Source: http://arxiv.org/abs/0808.2519v2

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43

Sep 21, 2013
09/13

Sep 21, 2013
by
A. Bazavov; C. Bernard; C. DeTar; X. Du; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; M. B. Oktay; R. Sugar; D. Toussaint; R. S. Van de Water

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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...

Source: http://arxiv.org/abs/1011.1792v1

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36

Sep 21, 2013
09/13

Sep 21, 2013
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; A. X. El-Khadra; E. D. Freeland; E. Gamiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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The experimentally measured rates of the semileptonic decays K -> pi l nu and D -> K(pi) l nu can be combined with lattice calculations of the associated form factors to precisely extract the CKM matrix elements |V_{us}| and |V_{cs(d)}|. We report on the status of form factor calculations with Fermilab charm quarks and staggered light quarks on the 2+1 flavor asqtad staggered MILC ensembles. Analysis of data for the D -> pi l nu form factor provides a nontrivial test of our methods via...

Source: http://arxiv.org/abs/1011.2423v1

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42

Sep 21, 2013
09/13

Sep 21, 2013
by
Jon A. Bailey; A. Bazavov; C. Bernard; C. M. Bouchard; C. DeTar; A. X. El-Khadra; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; M. B. Oktay; J. N. Simone; R. Sugar; D. Toussaint; R. S. Van de Water

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We present an update of our calculation of the form factor for B -> D* l nu at zero recoil, with higher statistics and finer lattices. As before, we use the Fermilab action for b and c quarks, the asqtad staggered action for light valence quarks, and the MILC ensembles for gluons and light quarks (L\"uscher-Weisz married to 2+1 rooted staggered sea quarks). In this update, we have reduced the total uncertainty on F(1) from 2.6% to 1.7%. At Lattice2010 we presented a still-blinded...

Source: http://arxiv.org/abs/1011.2166v1

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Sep 20, 2013
09/13

Sep 20, 2013
by
C. Bernard; T. Burch; C. DeTar; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. Osborn; R. Sugar; D. Toussaint

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We report on a lattice determination of the mass of the exotic $1^{-+}$ hybrid meson using an improved Kogut-Susskind action. Results from both quenched and dynamical quark simulations are presented. We also compare with earlier results using Wilson quarks at heavier quark masses. The results on lattices with three flavors of dynamical quarks show effects of sea quarks on the hybrid propagators which probably result from coupling to two meson states. We extrapolate the quenched results to the...

Source: http://arxiv.org/abs/hep-lat/0301024v2

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42

Sep 20, 2013
09/13

Sep 20, 2013
by
C. Aubin; C. Bernard; C. DeTar; M. Di Pierro; E. D. Freeland; Steven Gottlieb; U. M. Heller; J. E. Hetrick; A. X. El-Khadra; A. S. Kronfeld; L. Levkova; P. B. Mackenzie; D. Menscher; F. Maresca; M. Nobes; M. Okamoto; D. Renner; J. Simone; R. Sugar; D. Toussaint; H. D. Trottier

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We present the first lattice QCD calculation with realistic sea quark content of the D^+ meson decay constant f_{D^+}. We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f_{D^+} = 201 +/- 3 +/- 17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f_{D_s} = 249 +/- 3 +/- 16 MeV for the D_s meson.

Source: http://arxiv.org/abs/hep-lat/0506030v2

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Sep 20, 2013
09/13

Sep 20, 2013
by
MILC Collaboration; C. Bernard; C. DeTar; Steven Gottlieb; Urs M. Heller; J. E. Hetrick; C. McNeile; K. Rummukainen; R. Sugar; D. Toussaint

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We made an extensive study of the light hadron spectrum using the Wilson gauge action and Kogut-Susskind quarks. Using both dynamical quarks and the quenched approximation, we determine hadron masses for five and four gauge couplings respectively, with at least five quark masses at each coupling. In the continuum limit, we find a significant difference between two flavors of dynamical quarks and the quenched approximation for a range of quark masses.

Source: http://arxiv.org/abs/hep-lat/9810035v1

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Sep 20, 2013
09/13

Sep 20, 2013
by
J. N. Simone; C. Aubin; C. Bernard; C. DeTar; M. di Pierro; A. X. El-Khadra; Steven Gottlieb; E. B. Gregory; U. M. Heller; J. E. Hetrick; A. S. Kronfeld; P. B. Mackenzie; D. P. Menscher; M. Nobes; M. Okamoto; M. B. Oktay; J. Osborn; R. Sugar; D. Toussaint; H. D. Trottier; :; The Fermilab Lattice; MILC; HPQCD Collaborations

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We determine the leptonic decay constants in three flavor unquenched lattice QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm quarks in the Fermilab heavy quark formalism. Our preliminary results, based upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is statistical while the is the combined systematic uncertainty.

Source: http://arxiv.org/abs/hep-lat/0410030v1