2
2.0

Jun 30, 2018
06/18

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

texts

######
eye 2

######
favorite 0

######
comment 0

We compute the $B\to\pi\ell\nu$ semileptonic form factors and update the determination of the CKM matrix element $|V_{ub}|$. We use the MILC asqtad ensembles with $N_f=2+1$ sea quarks at four different lattice spacings in the range $a \approx 0.045$~fm to $0.12$~fm. The lattice form factors are extrapolated to the continuum limit using SU(2) staggered chiral perturbation theory in the hard pion limit, followed by an extrapolation in $q^2$ to the full kinematic range using a functional...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.6038

2
2.0

Jun 30, 2018
06/18

Jun 30, 2018
by
A. Bazavov; C. Bernard; C. 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. L. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 2

######
favorite 0

######
comment 0

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. We use the MILC highly improved staggered quark (HISQ) ensembles with four dynamical quark flavors. Our primary results are $f_{D^+} = 212.6(0.4)({}^{+1.0}_{-1.2})\ \mathrm{MeV}$, $f_{D_s} = 249.0(0.3)({}^{+1.1}_{-1.5})\ \mathrm{MeV}$, and $f_{D_s}/f_{D^+} = 1.1712(10)({}^{+29}_{-32})$, where the errors are statistical and total systematic,...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.2667

3
3.0

Jun 30, 2018
06/18

Jun 30, 2018
by
A. Bazavov; C. Bernard; N. Brown; C. DeTar; J. Foley; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Komijani; J. Laiho; L. Levkova; M. Oktay; R. L. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 3

######
favorite 0

######
comment 0

We report on a preliminary scale determination with gradient-flow techniques on the $N_f = 2 + 1 + 1$ HISQ ensembles generated by the MILC collaboration. The ensembles include four lattice spacings, ranging from 0.15 to 0.06 fm, and both physical and unphysical values of the quark masses. The scales $\sqrt{t_0}/a$ and $w_0/a$ are computed using Symanzik flow and the cloverleaf definition of $\langle E \rangle$ on each ensemble. Then both scales and the meson masses $aM_\pi$ and $aM_K$ are...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1411.0068

5
5.0

Jun 30, 2018
06/18

Jun 30, 2018
by
S. Basak; A. Bazavov; C. Bernard; C. DeTar; E. Freeland; J. Foley; Steven Gottlieb; U. M. Heller; J. Komijani; J. Laiho; L. Levkova; J. Osborn; R. L. Sugar; A. Torok; D. Toussaint; R. S. Van de Water; R. Zhou; for the MILC Collaboration

texts

######
eye 5

######
favorite 0

######
comment 0

We report on the MILC Collaboration calculation of electromagnetic effects on light pseudoscalar mesons. The simulations employ asqtad staggered dynamical quarks in QCD plus quenched photons, with lattice spacings varying from 0.12 to 0.06 fm. Finite volume corrections for the MILC realization of lattice electrodynamics have been calculated in chiral perturbation theory and applied to the lattice data. These corrections differ from those calculated by Hayakawa and Uno because our treatment of...

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

Source: http://arxiv.org/abs/1409.7139

2
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

texts

######
eye 2

######
favorite 0

######
comment 0

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

texts

######
eye 3

######
favorite 0

######
comment 0

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

2
2.0

Jun 30, 2018
06/18

Jun 30, 2018
by
A. Bazavov; C. Bernard; C. 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; D. Mohler; E. T. Neil; M. B. Oktay; S. Qiu; J. N. Simone; R. L. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 2

######
favorite 0

######
comment 0

We present a study of the $D$ and $B$ leptonic decay constants on the MILC $N_f=2+1$ asqtad gauge ensembles using asqtad-improved staggered light quarks and clover heavy quarks in the Fermilab interpretation. Our previous analysis \cite{Bazavov:2011aa} computed the decay constants at lattice spacings $a \approx 0.14, 0.11$ and $0.083$ fm. We have extended the simulations to finer $a \approx 0.058$ and $0.043$ fm lattice spacings, and have also increased statistics; this allows us to address...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1403.6796

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

texts

######
eye 3

######
favorite 0

######
comment 0

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

3
3.0

Jun 29, 2018
06/18

Jun 29, 2018
by
J. Komijani; A. Bazavov; C. Bernard; N. Brambilla; N. Brown; C. DeTar; D. Du; A. X. El-Khadra; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; A. S. Kronfeld; J. Laiho; P. B. Mackenzie; C. Monahan; Heechang Na; E. T. Neil; J. N. Simone; R. L. Sugar; D. Toussaint; A. Vairo; R. S. Van de Water

texts

######
eye 3

######
favorite 0

######
comment 0

We present a progress report on our calculation of the decay constants $f_B$ and $f_{B_s}$ from lattice-QCD simulations with highly-improved staggered quarks. Simulations are carried out with several heavy valence-quark masses on $(2+1+1)$-flavor ensembles that include charm sea quarks. We include data at six lattice spacings and several light sea-quark masses, including an approximately physical-mass ensemble at all but the smallest lattice spacing, 0.03 fm. This range of parameters provides...

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

Source: http://arxiv.org/abs/1611.07411

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

texts

######
eye 2

######
favorite 0

######
comment 0

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
S. Aoki; Y. Aoki; D. Becirevic; C. Bernard; T. Blum; G. Colangelo; M. Della Morte; P. Dimopoulos; S. Dürr; H. Fukaya; M. Golterman; Steven Gottlieb; S. Hashimoto; U. M. Heller; R. Horsley; A. Jüttner; T. Kaneko; L. Lellouch; H. Leutwyler; C. -J. D. Lin; V. Lubicz; E. Lunghi; R. Mawhinney; T. Onogi; C. Pena; C. T. Sachrajda; S. R. Sharpe; S. Simula; R. Sommer; A. Vladikas; U. Wenger; H. Wittig

texts

######
eye 2

######
favorite 0

######
comment 0

We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in the semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for...

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

Source: http://arxiv.org/abs/1607.00299

3
3.0

Jun 29, 2018
06/18

Jun 29, 2018
by
MILC Collaboration; S. Basak; A. Bazavov; C. Bernard; C. DeTar; E. Freeland; J. Foley; Steven Gottlieb; U. M. Heller; J. Komijani; J. Laiho; L. Levkova; J. Osborn; R. L. Sugar; A. Torok; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 3

######
favorite 0

######
comment 0

The MILC Collaboration has completed production running of electromagnetic effects on light mesons using asqtad improved staggered quarks. In these calculations, we use quenched photons in the noncompact formalism. We study four lattice spacings from $\approx\!0.12\:$fm to $\approx\!0.045\:$fm. To study finite-volume effects, we used six spatial lattice sizes $L/a=12$, 16, 20, 28, 40, and 48, at $a\!\approx\!0.12\:$fm. We update our preliminary values for the correction to Dashen's theorem...

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

Source: http://arxiv.org/abs/1606.01228

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

texts

######
eye 2

######
favorite 0

######
comment 0

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

3
3.0

Jun 28, 2018
06/18

Jun 28, 2018
by
Fermilab Lattice; MILC Collaborations; :; A. Bazavov; C. Bernard; C. Bouchard; N. Brown; C. DeTar; D. Du; A. X. El-Khadra; E. D. Freeland; E. Gámiz; Steven Gottlieb; U. M. Heller; J. Komijani; A. S. Kronfeld; J. Laiho; L. Levkova; P. B. Mackenzie; C. Monahan; T. Primer; Heechang Na; E. T. Neil; J. N. Simone; R. L. Sugar; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 3

######
favorite 0

######
comment 0

We give a progress report on a project aimed at a high-precision calculation of the decay constants $f_B$ and $f_{B_s}$ from simulations with HISQ heavy and light valence and sea quarks. Calculations are carried out with several heavy valence-quark masses on ensembles with 2+1+1 flavors of HISQ sea quarks at five lattice spacings and several light sea-quark mass ratios $m_{ud}/m_s$, including approximately physical sea-quark masses. This range of parameters provides excellent control of the...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1511.02294

7
7.0

Jun 28, 2018
06/18

Jun 28, 2018
by
MILC Collaboration; S. Basak; A. Bazavov; C. Bernard; C. DeTar; E. Freeland; J. Foley; Steven Gottlieb; U. M. Heller; J. Komijani; J. Laiho; L. Levkova; R. Li; J. Osborn; R. L. Sugar; A. Torok; D. Toussaint; R. S. Van de Water; R. Zhou

texts

######
eye 7

######
favorite 0

######
comment 0

For some time, the MILC Collaboration has been studying electromagnetic effects on light mesons. These calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in XPT. That is, the sea quarks are electrically neutral, while the valence quarks carry charge. For the photons we use the non-compact formalism. We have new results with lattice spacing as small as 0.045 fm and a large range of volumes. We consider how well chiral perturbation theory describes these...

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

Source: http://arxiv.org/abs/1510.04997

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

texts

######
eye 11

######
favorite 0

######
comment 0

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

texts

######
eye 10

######
favorite 0

######
comment 0

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

texts

######
eye 5

######
favorite 0

######
comment 0

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

texts

######
eye 8

######
favorite 0

######
comment 0

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

5
5.0

Jun 27, 2018
06/18

Jun 27, 2018
by
MILC Collaboration; A. Bazavov; C. Bernard; N. Brown; C. DeTar; J. Foley; Steven Gottlieb; U. M. Heller; J. Komijani; J. Laiho; L. Levkova; R. L. Sugar; D. Toussaint; R. S. Van de Water

texts

######
eye 5

######
favorite 0

######
comment 0

We report on a scale determination with gradient-flow techniques on the $N_f=2+1+1$ highly improved staggered quark ensembles generated by the MILC Collaboration. The ensembles include four lattice spacings, ranging from approximately 0.15 to 0.06 fm, and both physical and unphysical values of the quark masses. The scales $\sqrt{t_0}/a$ and $w_0/a$ and their tree-level improvements, $\sqrt{t_{0,{\rm imp}}}$ and $w_{0,{\rm imp}}$, are computed on each ensemble using Symanzik flow and the...

Topic: High Energy Physics - Lattice

Source: http://arxiv.org/abs/1503.02769

48
48

Sep 24, 2013
09/13

Sep 24, 2013
by
C. Bernard; T. DeGrand; C. DeTar; S. Gottlieb; U. M. Heller; J. Hetrick; P. Lacock; K. Orginos; R. L. Sugar; D. Toussaint

texts

######
eye 48

######
favorite 0

######
comment 0

The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or "string", which should break in the presence of light quark-antiquark pairs. This expected zero-temperature phenomenon has proven elusive in simulations of lattice QCD. We study mixing between the string state and the two-meson decay channel in QCD with two flavors of dynamical sea quarks. We confirm that mixing is weak and find that it decreases at level crossing. While our study does not...

Source: http://arxiv.org/abs/hep-lat/0103012v2

32
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

texts

######
eye 32

######
favorite 0

######
comment 0

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

54
54

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

texts

######
eye 54

######
favorite 0

######
comment 0

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

32
32

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

texts

######
eye 32

######
favorite 0

######
comment 0

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

42
42

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

texts

######
eye 42

######
favorite 0

######
comment 0

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

90
90

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

texts

######
eye 90

######
favorite 0

######
comment 0

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

44
44

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

texts

######
eye 44

######
favorite 0

######
comment 0

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

36
36

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

texts

######
eye 36

######
favorite 0

######
comment 0

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

53
53

Sep 23, 2013
09/13

Sep 23, 2013
by
S. Collins; U. M. Heller; J. Sloan; J. Shigemitsu; A. Ali Khan; C. T. H. Davies

texts

######
eye 53

######
favorite 0

######
comment 0

We present a lattice investigation of the heavy-light meson decay constants using Wilson light quarks and NRQCD heavy quarks, partially including the effects of dynamical sea quarks. We calculate the pseudoscalar and vector decay constants over a wide range in heavy quark mass and are able to perform a detailed analysis of heavy quark symmetry. We find consistency between the extrapolation of the NRQCD results and the static case, as expected. We find the slope of the decay constants with $1/M$...

Source: http://arxiv.org/abs/hep-lat/9607004v1

39
39

Sep 23, 2013
09/13

Sep 23, 2013
by
K. M. Bitar; R. G. Edwards; U. M. Heller; A. D. Kennedy

texts

######
eye 39

######
favorite 0

######
comment 0

We study QCD with two flavors of dynamical Wilson fermions at $\beta = 5.5$ and three values of $\kappa$. The corresponding pion masses are 0.375, 0.324 and 0.262 in lattice units, with pion to rho mass ratios of 0.76, 0.71 and 0.62, respectively. We use the configurations to compute the heavy quark potential, leading to lattice spacings of 0.110, 0.105 and 0.099 fm, and to compute spectroscopy for several different valence quark $\kappa$'s.

Source: http://arxiv.org/abs/hep-lat/9607043v1

34
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

texts

######
eye 34

######
favorite 0

######
comment 0

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

texts

######
eye 51

######
favorite 0

######
comment 0

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

42
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

texts

######
eye 42

######
favorite 0

######
comment 0

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

59
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

texts

######
eye 59

######
favorite 0

######
comment 0

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

42
42

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; C. DeTar; S. Gottlieb; U. M. Heller; J. Hetrick; K. Rummukainen; R. L. Sugar; D. Toussaint

texts

######
eye 42

######
favorite 0

######
comment 0

Quantum chromodynamics with two zero-mass flavors is expected to exhibit a phase transition with O(4) critical behavior. Fixing the universality class is important for phenomenology and for facilitating the extrapolation of simulation data to physical quark mass values. Other groups have reported results from lattice QCD simulations with dynamical staggered quarks at Nt = 4, which suggest a departure from the expected critical behavior. We have pushed simulations to the largest volumes and...

Source: http://arxiv.org/abs/hep-lat/9908008v2

36
36

Sep 23, 2013
09/13

Sep 23, 2013
by
P. H. Damgaard; U. M. Heller; K. Splittorff

texts

######
eye 36

######
favorite 0

######
comment 0

The microscopic spectral density of the Hermitian Wilson-Dirac operator is computed numerically in quenched lattice QCD. We demonstrate that the results given for fixed index of the Wilson-Dirac operator can be matched by the predictions from Wilson chiral perturbation theory. We test successfully the finite volume and the mass scaling predicted by Wilson chiral perturbation theory at fixed lattice spacing.

Source: http://arxiv.org/abs/1110.2851v2

38
38

Sep 23, 2013
09/13

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

texts

######
eye 38

######
favorite 0

######
comment 0

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 chi^2/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...

Source: http://arxiv.org/abs/1111.4314v1

44
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

texts

######
eye 44

######
favorite 0

######
comment 0

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

34
34

Sep 23, 2013
09/13

Sep 23, 2013
by
H. Ohno; U. M. Heller; F. Karsch; S. Mukherjee

texts

######
eye 34

######
favorite 0

######
comment 0

We report on the behavior of the eigenvalue distribution of the Dirac operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We calculate the eigenvalue density at several values of the temperature close to the pseudocritical temperature. For this study we use gauge field configurations generated on lattices of size $32^3 \times 8$ with two light quark masses corresponding to pion masses of about 160 and 115 MeV. We find that the eigenvalue density below $T_c$ receives large...

Source: http://arxiv.org/abs/1111.1939v1

34
34

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; M. Oktay; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water

texts

######
eye 34

######
favorite 0

######
comment 0

We report on the status of a program of generating and using configurations with four flavors of dynamical quarks, using the HISQ action. We study the lattice spacing dependence of physical quantities in these simulations, using runs at several lattice spacings, but with the light quark mass held fixed at two tenths of the strange quark mass. 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...

Source: http://arxiv.org/abs/1012.1265v1

67
67

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

texts

######
eye 67

######
favorite 0

######
comment 0

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

42
42

Sep 23, 2013
09/13

Sep 23, 2013
by
R. Höllwieser; M. Faber; U. M. Heller

texts

######
eye 42

######
favorite 0

######
comment 0

We analyze topological charge contributions from classical SU(2) center vortices with shapes of planes and spheres using different topological charge definitions, namely the center vortex picture of topological charge, a discrete version of F\~{F} in the plaquette and hypercube definitions and the lattice index theorem. For the latter the zeromodes of the Dirac operator in the fundamental and adjoint representations using both the overlap and asqtad staggered fermion formulations are...

Source: http://arxiv.org/abs/1202.0929v3

49
49

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

texts

######
eye 49

######
favorite 0

######
comment 0

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

36
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

texts

######
eye 36

######
favorite 0

######
comment 0

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

36
36

Sep 23, 2013
09/13

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

texts

######
eye 36

######
favorite 0

######
comment 0

As part of a larger project to estimate the fB decay constant, we are recalculating fB_static using a variational smearing method in an effort to improve accuracy. Preliminary results for the static B_B parameter and HQET two point functions are also presented.

Source: http://arxiv.org/abs/hep-lat/9608088v1

39
39

Sep 23, 2013
09/13

Sep 23, 2013
by
C. Bernard; T. Blum; C. E. DeTar; Steven Gottlieb; U. M. Heller; J. E. Hetrick; L. Karkkainen; C. McNeile; K. Rummukainen; R. L. Sugar; D. Toussaint; M. Wingate

texts

######
eye 39

######
favorite 0

######
comment 0

We conclude our analysis of the N_t=6 equation of state for two flavor QCD, first described at last year's conference. We have obtained new runs at am_q=0.025 and improved runs at am_q=0.0125. The results are extrapolated to m_q=0, and we extract the speed of sound as well. We also present evidence for a restoration of the SU(2) X SU(2) chiral symmetry just above the crossover, but not of the axial U(1) chiral symmetry.

Source: http://arxiv.org/abs/hep-lat/9608026v1

52
52

Sep 23, 2013
09/13

Sep 23, 2013
by
S. Collins; U. M. Heller; J. Sloan; J. Shigemitsu; A. Ali Khan; C. T. H. Davies

texts

######
eye 52

######
favorite 0

######
comment 0

We present results for the spectrum and decay constants of B mesons from NRQCD using dynamical configurations at $\beta=5.6$ with two flavours of staggered fermions. The light quarks are generated using the Clover action with tadpole improvement.

Source: http://arxiv.org/abs/hep-lat/9608064v1

43
43

Sep 23, 2013
09/13

Sep 23, 2013
by
LHP Collaboration; S. Basak; R. Edwards; R. Fiebig; G. Fleming; U. M. Heller; C. Morningstar; D. Richards; I. Sato; S. Wallace

texts

######
eye 43

######
favorite 0

######
comment 0

The construction of the operators and correlators required to determine the excited baryon spectrum is presented, with the aim of exploring the spatial and spin structure of the states while minimizing the number of propagator inversions. The method used to construct operators that transform irreducibly under the symmetries of the lattice is detailed, and the properties of example operators are studied using domain-wall fermion valence propagators computed on MILC asqtad dynamical lattices.

Source: http://arxiv.org/abs/hep-lat/0312003v1

50
50

Sep 23, 2013
09/13

Sep 23, 2013
by
P. H. Damgaard; U. M. Heller; R. Niclasen; K. Rummukainen

texts

######
eye 50

######
favorite 0

######
comment 0

We classify SU(3) gauge field configurations in different topological sectors by the smearing technique. In each sector we compute the distribution of low lying eigenvalues of the staggered Dirac operator. In all sectors we find perfect agreement with the predictions for the sector of topological charge zero. The smallest Dirac operator eigenvalues of staggered fermions at presently realistic lattice couplings are thus insensitive to gauge field topology. On the smeared configurations, $4\nu$...

Source: http://arxiv.org/abs/hep-lat/9909017v1

39
39

Sep 23, 2013
09/13

Sep 23, 2013
by
P. H. Damgaard; R. G. Edwards; U. M. Heller; R. Narayanan

texts

######
eye 39

######
favorite 0

######
comment 0

In the large-volume limit $V\to\infty$ with $V < < 1/m_{\pi}^4$ the mass-dependent chiral condensate is predicted to satisfy exact finite-volume scaling laws that fall into three major universality classes. We test these analytical predictions with staggered fermions and overlap fermions in gauge field sectors of fixed topological charge $\nu$.

Source: http://arxiv.org/abs/hep-lat/9909009v1