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ABSTRACT: We determine the strange quark condensate from lattice QCD for the first time
and compare its value to that of the light quark and chiral condensates. The
results come from a direct calculation of the expectation value of the trace of
the quark propagator followed by subtraction of the appropriate perturbative
contribution, derived here, to convert the non-normal-ordered $m\bar{\psi}\psi$
to the $\bar{MS}$ scheme at a fixed scale. This is then a well-defined physical
`nonperturbative' condensate that can be used in the Operator Product Expansion
of current-current correlators. The perturbative subtraction is calculated
through $\mathcal{O}(\alpha_s)$ and estimates of higher order terms are
included through fitting results at multiple lattice spacing values. The gluon
field configurations used are `second generation' ensembles from the MILC
collaboration that include 2+1+1 flavors of sea quarks implemented with the
Highly Improved Staggered Quark action and including $u/d$ sea quarks down to
physical masses. Our results are : $<\bar{s}{s}>^{\bar{MS}}(2 \mathrm{GeV})=
-(290(15) \mathrm{MeV})^3$, $<\bar{l}{l}>^{\bar{MS}}(2\, \mathrm{GeV})=
-(283(2) \mathrm{MeV})^3$, where $l$ is a light quark with mass equal to the
average of the $u$ and $d$ quarks. The strange to light quark condensate ratio
is 1.08(16). The light quark condensate is significantly larger than the chiral
condensate in line with expectations from chiral analyses. We discuss the
implications of these results for other calculations.
11/2012;
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I. F. Allison,
K. Y. Wong,
C. T. H. Davies,
C. McNeile, H. D. Trottier,
E. Dalgic,
J. Wu,
E. Follana,
R. R. Horgan,
G. P. Lepage,
J. Shigemitsu,
for the HPQCD collaboration
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ABSTRACT: We provide a new determination of the charm quark mass using the Highly Improved Staggered Quark (HISQ) action, finding m_c(3 GeV) = 0.983(23) GeV. Our determination makes extensive use of second order lattice perturbation theory in matching the bare lattice mass to the MSbar scheme. This matching utilises both traditional diagrammatic perturbation theory and weak coupling simulations. The second of these techniques allows us to extract perturbative coefficients from Monte-Carlo simulations and the process of doing this is laid out in some detail here. Comment: 7 pages, 4 figures, talk presented at the XXVI International Symposium on Lattice Field Theory, July 14-19, 2008, Williamsburg, Virginia, USA
10/2008;
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ABSTRACT: The effects of unquenching on the perturbative improvement coefficients in the Symanzik action are computed within the framework of L\"uscher-Weisz on-shell improvement. We find that the effects of quark loops are surprisingly large, and their omission may well explain the scaling violations observed in some unquenched studies.
09/2007;
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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, [......],
P B Mackenzie,
D Menscher,
F Maresca,
M Nobes,
M Okamoto,
D Renner,
J Simone,
R Sugar,
D Toussaint, H D Trottier
[show abstract]
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ABSTRACT: 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(Ds)=249+/-3+/-16 MeV for the Ds meson.
Physical Review Letters 10/2005; 95(12):122002. · 7.37 Impact Factor
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Andreas S. Kronfeld,
I. F. Allison,
C. Aubin,
C. Bernard,
C. T. H. Davies,
C. DeTar,
M. Di Pierro,
E. D. Freeland,
Steven Gottlieb,
A. Gray, [......],
D. Menscher,
M. Nobes,
M. Okamoto,
M. B. Oktay,
J. Osborn,
D. Renner,
J. N. Simone,
R. Sugar,
D. Toussaint, H. D. Trottier
[show abstract]
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ABSTRACT: In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the $q^2$ dependence of the form factor in semileptonic $D\to Kl\nu$ decay, the decay constant of the $D$ meson, and the mass of the $B_c$ meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments. Comment: v1: talk given at the International Conference on QCD and Hadronic Physics, Beijing, June 16-20, 2005; v2: poster presented at the XXIIIrd International Symposium on Lattice Field Theory, Dublin, July 25-30
09/2005;
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[show abstract]
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ABSTRACT: We obtain a new value for the QCD coupling constant by combining lattice QCD simulations with experimental data for hadron masses. Our lattice analysis is the first to (1) include vacuum polarization effects from all three light-quark flavors (using MILC configurations), (2) include third-order terms in perturbation theory, (3) systematically estimate fourth and higher-order terms, (4) use an unambiguous lattice spacing, and (5) use an [symbol: see text](a2)-accurate QCD action. We use 28 different (but related) short-distance quantities to obtain alpha((5)/(MS))(M(Z)) = 0.1170(12).
Physical Review Letters 08/2005; 95(5):052002. · 7.37 Impact Factor
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C Aubin,
C Bernard,
C Detar,
M Dipierro,
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
[show abstract]
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ABSTRACT: We present the first three-flavor lattice QCD calculations for D-->pilnu and D-->Klnu 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. Our results for the form factors at q(2)=0 are f(D-->pi)(+)(0)=0.64(3)(6) and f(D-->K)(+)(0)=0.73(3)(7), where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the Cabibbo-Kobayashi-Maskawa matrix elements |V(cd)|=0.239(10)(24)(20) and |V(cs)|=0.969(39)(94)(24), where the last errors are from experimental uncertainties.
Physical Review Letters 01/2005; 94(1):011601. · 7.37 Impact Factor
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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
[show abstract]
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ABSTRACT: 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 $|V_{cd}|$, $|V_{cs}|$, $|V_{cb}|$ and $|V_{ub}|$. We also check CKM unitarity, for the first time, using only lattice QCD as the theoretical input.
10/2004;
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C T H Davies,
E Follana,
A Gray,
G P Lepage,
Q Mason,
M Nobes,
J Shigemitsu, H D Trottier,
M Wingate,
C Aubin, [......],
J E Hetrick,
J Osborn,
R Sugar,
D Toussaint,
M Di Pierro,
A El-Khadra,
A S Kronfeld,
P B Mackenzie,
D Menscher,
J Simone
[show abstract]
[hide abstract]
ABSTRACT: The recently developed Symanzik-improved staggered-quark discretization allows unquenched lattice-QCD simulations with much smaller (and more realistic) quark masses than previously possible. To test this formalism, we compare experiment with a variety of nonperturbative calculations in QCD drawn from a restricted set of "gold-plated" quantities. We find agreement to within statistical and systematic errors of 3% or less. We discuss the implications for phenomenology and, in particular, for heavy-quark physics.
Physical Review Letters 02/2004; 92(2):022001. · 7.37 Impact Factor
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ABSTRACT: Perturbative coefficients for Wilson loops and the static-quark self-energy are extracted from Monte Carlo simulations at weak coupling. The lattice volumes and couplings are chosen to ensure that the lattice momenta are all perturbative. Twisted boundary conditions are used to eliminate the effects of lattice zero modes and to suppress nonperturbative finite-volume effects due to Z(3) phases. Simulations of the Wilson gluon action are done with both periodic and twisted boundary conditions, and over a wide range of lattice volumes (from $3^4$ to $16^4$) and couplings (from $\beta \approx 9$ to $\beta \approx 60$). A high precision comparison is made between the simulation data and results from finite-volume lattice perturbation theory. The Monte Carlo results are shown to be in excellent agreement with perturbation theory through second order. New results for third-order coefficients for a number of Wilson loops and the static-quark self-energy are reported. Comment: 36 pages, 15 figures, REVTEX document
11/2001;
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ABSTRACT: Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large beta on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z_3 tunneling.
11/1999;
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[show abstract]
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ABSTRACT: Calculations of the chiral condensate on the lattice using staggered fermions and the Lanczos algorithm are presented. Four gauge fields are considered: the quenched non-Abelian field, an Abelian projected field, and monopole and photon fields further decomposed from the Abelian field. Abelian projection is performed in maximal Abelian gauge and in Polyakov gauge. The results show that monopoles in maximal Abelian gauge largely reproduce the chiral condensate values of the full non-Abelian theory, in both SU(2) and SU(3) color. Comment: 13 pages in RevTex including 6 figures, uucompressed, self-extracting
09/1995;
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P B Mackenzie,
C Aubin,
C Bernard,
C Detar,
M Di Pierro,
Steven Gottlieb,
E Gregory,
U M Heller,
J E Hetrick,
A X El-Khadra, [......],
D Menscher,
M Nobes,
M Okamoto,
M B Oktay,
J Osborn,
D Renner,
J N Simone,
R Sugar,
D Toussaint, H D Trottier
[show abstract]
[hide abstract]
ABSTRACT: Fermilab Lattice, MILC, and HPQCD Collaborations We have calculated the semileptonic form factors of B and D mesons using unquenched, im-proved staggered light quarks, and improved clover heavy quarks. We discuss the use of unitarity constraints to bound the form factors in the high recoil momentum region.
01/2002;
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[show abstract]
[hide abstract]
ABSTRACT: Perturbative coefficients for Wilson loops and the static quark self-energy are extracted from Monte Carlo simulations at large β on finite volumes, where all the lattice momenta are large. The Monte Carlo results are in excellent agreement with perturbation theory through second order. New results for third order coefficients are reported. Twisted boundary conditions are used to eliminate zero modes and to suppress Z3 tunneling.
Nuclear Physics B - Proceedings Supplements.
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[show abstract]
[hide abstract]
ABSTRACT: We present the first lattice QCD calculation with realistic sea quark content of the D+-meson decay constant fD+. 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 fD+ = 201 + 3 + 17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain fDs = 249 + 3 + 16 MeV for the Ds meson.
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[show abstract]
[hide abstract]
ABSTRACT: We determine the leptonic decay constants fDs and fD in three flavor unquenched lattice QCD. We use O(a2)-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 fDs = 263+5 −9 ± 24 MeV and fD = 225+11 −13 ± 21 MeV. In each case, the first reported error is statistical while the second is the combined systematic uncertainty.
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ABSTRACT: We present the first three-flavor lattice QCD calculations for D→ rrlv and D→ Klv 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. Our results for the form factors at q2 = 0 are fD→rr(0)= 0:64(3)(6) and fD→K (0) = 0:73(3)(7), where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the Cabibbo-Kobayashi-Maskawa matrix elements [Vcd] = 0:239(10)(24)(20) and [Vcs]= 0.969(39)(94)(24), where the last errors are from experimental uncertainties.
